/var
|- account/
|- arpwatch/
|- cache/
|- crash/
|- db/
|- empty/
|- ftp/
|- gdm/
|- kerberos/
|- lib/
|- local/
|- lock/
|- log/
|- mail -> spool/mail/
|- mailman/
|- named/
|- nis/
|- opt/
|- preserve/
|- run/
+- spool/
|- at/
|- clientmqueue/
|- cron/
|- cups/
|- lpd/
|- mail/
|- mqueue/
|- news/
|- postfix/
|- repackage/
|- rwho/
|- samba/
|- squid/
|- squirrelmail/
|- up2date/
|- uucppublic/
|- vbox/
|- tmp/
|- tux/
|- www/
|- yp/
/usr
/usr usually contains by far the largest share of data on a system. Hence,
this is one of the most important directories in the system as it contains
all the user binaries, their documentation, libraries, header files, etc....
X and its supporting libraries can be found here. User programs like telnet,
ftp, etc.... are also placed here. In the original Unix implementations, /usr
was where the home directories of the users were placed (that is to say,
/usr/someone was then the directory now known as /home/someone). In current
Unices, /usr is where user-land programs and data (as opposed to 'system land'
programs and data) are. The name hasn't changed, but it's meaning has narrowed
and lengthened from "everything user related" to "user usable programs and data".
As such, some people may now refer to this directory as meaning 'User System Resources'
and not 'user' as was originally intended.
/usr is shareable, read-only data. That means that /usr should
be shareable between various FHS-compliant hosts and must not be written to.
Any information that is host-specific or varies with time is stored elsewhere.
Large software packages must not use a direct subdirectory under the /usr
hierarchy.
|
- /usr/X11R6
-
-
Another large
subdirectory structure begins here, containing libraries, executables,
docs, fonts and much more concerning the X Window System. Its inclusion
here is somewhat inconsistent and so is the difference between '/usr'
and '/usr/X11R6' directories. One would assume that programs that run on
X only have their files in the '/usr/X11R6' hierarchy, while the others
use '/usr'. Regrettably, it isn't so. KDE and GNOME put their files in
the '/usr' hierarchy, whereas the window manager Window Maker uses
'/usr/X11R6'. Documentation files for X11R6 are not in '/usr/X11R6/doc',
but primarily in '/usr/X11R6/lib/X11/doc'. This mess is due to the fact
that in contrast to other operating systems, the graphical desktop
isn't an integral part of the system. Linux is still primarily used on
servers, where graphical systems don't make sense.
-
This hierarchy is reserved for the X Window System, version 11 release
6, and related files. To simplify matters and make XFree86 more
compatible with the X Window System on other systems, the following
symbolic links must be present if /usr/X11R6 exists:
/usr/bin/X11 -> /usr/X11R6/bin
/usr/lib/X11 -> /usr/X11R6/lib/X11
/usr/include/X11 -> /usr/X11R6/include/X11
|
-
In
general, software must not be installed or managed via the above
symbolic links. They are intended for utilization by users only. The
difficulty is related to the release version of the X Window System - in
transitional periods, it is impossible to know what release of X11 is
in use.
- /usr/X11R6/bin
-
XFree86 system binaries.
These are necessary for the initialisation, configuration and running of
the X windowing system. X, xf86config, xauth, xmodmap and even xpenguin
are located here.
- /usr/X11R6/include
-
XFree86 system header files. There are required for the compilation of some applications that utilise the X toolkit.
- /usr/X11R6/lib
-
XFree86 system libraries.
- /usr/X11R6/lib/modules
-
XFree86 system modules. These are the modules that X loads upon startup.
Without these modules video4linux, DRI and GLX extensions and drivers
for certain input devices would cease to function.
- /usr/X11R6/lib/X11/fonts
-
XFree86 system fonts. Fonts that are utilised by 'xfs' (the X Font Server) and programs of that ilk.
- /usr/bin
-
This directory contains the vast majority of binaries on your system.
Executables in this directory vary widely. For instance vi, gcc,
gnome-session and mozilla and are all found here.
- /usr/doc
-
The central documentation directory. Documentation is actually located in /usr/share/doc and linked from here.
- /usr/etc
-
Theoretically, that's another directory for configuration files. Virtually unused now.
- /usr/games
-
Once upon a time, this directory contained network games files. Rarely used now.
- /usr/include
-
The directory for 'header files', needed for compiling user space source code.
- /usr/include/'package-name'
-
Application specific header files.
- /usr/info
-
This directory used to contain the files for the info documentation system. Now they are in '/usr/share/info'.
- /usr/lib
-
This directory contains program libraries. Libraries are collections of frequently used program routines.
- /usr/local
-
The original idea behind '/usr/local' was to have a separate ('local')
'/usr' directory on every machine besides '/usr', which might be just
mounted read-only from somewhere else. It copies the structure of
'/usr'. These days, '/usr/local' is widely regarded as a good place in
which to keep self-compiled or third-party programs.
The /usr/local hierarchy is for use by the system administrator when
installing software locally. It needs to be safe from being overwritten
when the system software is updated. It may be used for programs and
data that are shareable amongst a group of hosts, but not found in /usr.
Locally installed software must be placed within /usr/local rather than
/usr unless it is being installed to replace or upgrade software in
/usr.
- /usr/man
-
It once held the man pages. It has been moved to /usr/share/man.
- /usr/sbin
-
This directory contains programs for administering a system, meant to be
run by 'root'. Like '/sbin', it's not part of a user's $PATH. Examples
of included binaries here are chroot, useradd, in.tftpd and pppconfig.
- /usr/share
-
This directory contains 'shareable', architecture-independent files
(docs, icons, fonts etc). Note, however, that '/usr/share' is generally
not intended to be shared by different operating systems or by different
releases of the same operating system. Any program or package which
contains or requires data that doesn't need to be modified should store
that data in '/usr/share' (or '/usr/local/share', if installed locally).
It is recommended that a subdirectory be used in /usr/share for this
purpose."
- /usr/share/doc
-
Location of package
specific documentation files. These directories often contain useful
information that might not be in the man pages. They may also contain
templates and configuration files for certain utilities making
configuration that much easier.
- /usr/share/info
-
Location of 'info' pages. This style of documentation seems to be largely ignored now. Manual pages are in far greater favour.
- /usr/share/man
-
Manual pages. They are organised into 8 sections, which are explained below.
-
man1: User programs
Manual pages that describe publicly accessible commands are contained
in this chapter. Most program documentation that a user will need to
use is located here.
man2: System calls
This section describes all of the system calls (requests for the kernel
to perform operations).
man3: Library functions and subroutines
Section 3 describes program library routines that are not direct calls
to kernel services. This and chapter 2 are only really of interest to
programmers.
man4: Special files
Section 4 describes the special files, related driver functions, and
networking support available in the system. Typically, this includes
the device files found in /dev and the kernel interface to networking
protocol support.
man5: File formats
The formats for many data files are documented in the section 5. This
includes various include files, program output files, and system files.
man6: Games
This chapter documents games, demos, and generally trivial programs.
Different people have various notions about how essential this is.
man7: Miscellaneous Manual pages that are difficult to classify are
designated as being section 7. The troff and other text processing
macro packages are found here.
man8: System administration Programs used by system administrators
for system operation and maintenance are documented here. Some of
these programs are also occasionally useful for normal users.
|
- /usr/src
-
The 'linux' sub-directory holds the Linux kernel sources, header-files and documentation.
- /usr/src/RPM
-
RPM provides a substructure for building RPMs from SRPMs. Organisation
of this branch is fairly logical with packages being organised according
to a package's architecture.
- /usr/src/RPM/BUILD
-
A temporary store for RPM binary files that are being built from source code.
- /usr/src/RPM/RPMS/athlon,
/usr/src/RPM/RPMS/i386, /usr/src/RPM/RPMS/i486, /usr/src/RPM/RPMS/i586,
/usr/src/RPM/RPMS/i686, /usr/src/RPM/RPMS/noarch
-
These directories contain architecture dependant RPM source files.
- /usr/src/RPM/SOURCES
-
This directory contains the source TAR files, patches, and icon files for software to be packaged.
- /usr/src/RPM/SPECS
-
RPM SPEC files. A SPEC file is a file that contains information as well as scripts that are necessary to build a package.
- /usr/src/RPM/SRPMS
-
Contains the source RPM files which result from a build.
- /usr/src/linux
-
Contains the source code for the Linux kernel.
- /usr/src/linux/.config
-
The last kernel source configuration. This file is normally created
through the 'make config', 'make menuconfig' or 'make xconfig' steps
during kernel compilation.
- /usr/src/linux/.depend, /usr/src/linux/.hdepend
-
'make dep' checks the dependencies of the selections you made when you
created your .config file. It ensures that the required files can be
found and it builds a list that is to be used during compilation. Should
this process be successful these two files are created.
- /usr/src/linux/COPYING
-
GNU License
- /usr/src/linux/CREDITS
-
A partial credits-file of people that have contributed to the Linux
project. It is sorted by name and formatted to allow easy grepping and
beautification by scripts. The fields are: name (N), email (E),
web-address (W), PGP key ID and fingerprint (P), description (D), and
snail-mail address (S).
- /usr/src/linux/MAINTAINERS
-
List of maintainers and details on how to submit kernel changes.
- /usr/src/linux/Makefile
-
Contains data necessary for compilation of a working kernel. It allows
developers and end-users to compile a kernel with a few simple steps
(ie. make dep, make clean, make bzImage, make modules, make
modules_install) and also not have to worry about re-compiling
everything from scratch if parts of it have already been done so and are
up to date.
- /usr/src/linux/README
-
These are the
release notes for Linux version 2.4. Read them carefully, as they tell
you what this is all about, explain how to install the kernel, and what
to do if something goes wrong.
- /usr/src/linux/REPORTING-BUGS
-
A suggested procedure for reporting Linux bugs. You aren't obliged to
use the bug reporting format, it is provided as a guide to the kind of
information that can be useful to developers - no more.
- /usr/src/linux/Rules.make
-
This file contains rules which are shared between multiple Makefiles.
- /usr/src/linux/Documentation
-
Contains documentation that may be necessary in order to re-compile a
kernel. However, it also provides quite a lot of information about your
Linux system in general as well. For those who wish to seek further
information on the contents of this directory you may consult the
/usr/src/linux/Documentation/00-INDEX file. Further, more detailed
documentation may be found in /usr/src/linux/Documentation/Docbook. Of
course, the contents of this directory is written in Docbook but may be
converted to pdf, ps or html using the make targets of 'pdfdocs',
'psdocs' and 'htmldocs' respectively.
- /usr/tmp
-
User space temporary files. This directory is not found on modern
distributions at all and was most likely created as a consequence of
Linux's UNIX heritage
Red Hat Enterprise Linux uses the Filesystem Hierarchy Standard (FHS) file system structure, which defines the names, locations, and permissions for many file types and directories.
The FHS document is the authoritative reference to any FHS-compliant
file system, but the standard leaves many areas undefined or extensible.
This section is an overview of the standard and a description of the
parts of the file system not covered by
the standard.
Compliance with the standard means many things, but the two most
important are compatibility with other compliant systems and the ability
to mount a /usr/ partition as read-only. This second point is important
because the directory contains common executables and should not be changed by users. Also, since the /usr/ directory is mounted as read-only, it can be mounted from the CD-ROM or from another machine via a read-only
NFS mount.
The directories and files noted here are a small subset of those
specified by the FHS document. Refer to the latest FHS document for the
most complete information.
The complete standard is available online at http://www.pathname.com/fhs/.
1.2.1.1. The /boot/ Directory
The /boot/ directory contains static
files required to boot the system, such as the Linux kernel. These files
are essential for the system to boot properly.
Warning
Do not remove the /boot/ directory. Doing so renders the system unbootable.
1.2.1.2. The /dev/ Directory
The /dev/ directory contains device nodes
that either represent devices that are attached to the system or
virtual devices that are provided by the kernel. These device nodes are
essential for the system to function properly. The udev demon takes care of creating and removing all these device nodes in /dev/.
Devices in the /dev directory and
subdirectories are either character (providing only a serial stream of
input/output) or block (accessible randomly). Character devices include
mouse, keyboard, modem while block devices include hard disk, floppy
drive etc. If you have GNOME or KDE installed in your system, devices
such as external drives or cds are automatically detected when connected
(e.g via usb) or inserted (e.g via CD or DVD drive) and a popup window
displaying the contents is automatically displayed. Files in the /dev directory are essential for the system to function properly. Examples of common files in the /dev include:
/dev/hda - the master device on primary IDE channel.
/dev/hdb - the slave device on primary IDE channel.
/dev/tty0 - first virtual console.
/dev/tty1 - second virtual console.
/dev/sda - first device on primary SCSI or SATA channel.
/dev/lp0 - first parallel port.
1.2.1.3. The /etc/ Directory
The /etc/ directory is reserved for configuration files that are local to the machine. No binaries are to be placed in /etc/. Any binaries that were once located in /etc/ should be placed into /sbin/ or /bin/.
Examples of directories in /etc are the X11/ and skel/:
/etc
|- X11/
|- skel/
The /etc/X11/ directory is for X Window System configuration files, such as xorg.conf. The /etc/skel/
directory is for "skeleton" user files, which are used to populate a
home directory when a user is first created. Applications also store
their configuration files in this directory and may reference them when
they are executed.
1.2.1.4. The /lib/ Directory
The /lib/ directory should contain only those libraries needed to execute the binaries in /bin/ and /sbin/. These shared library images are
particularly important for booting the system and executing commands within the root file system.
1.2.1.5. The /media/ Directory
The /media/ directory contains
subdirectories used as mount points for removeable media such as usb
storage media, DVDs, CD-ROMs, and Zip disks.
1.2.1.6. The /mnt/ Directory
The /mnt/ directory is reserved for
temporarily mounted file systems, such as NFS file system mounts. For
all removeable media, please use the /media/ directory. Automatically detected removeable media will be mounted in the /media directory.
Note
The /mnt directory must not be used by installation programs.
1.2.1.7. The /opt/ Directory
The /opt/ directory provides storage for most application software packages.
A package placing files in the /opt/
directory creates a directory bearing the same name as the package. This
directory, in turn, holds files that otherwise would be scattered
throughout the file system, giving the system administrator an easy way
to determine the role of each file within a particular package.
For example, if sample is the name of a particular software package located within the /opt/ directory, then all of its files are placed in directories inside the /opt/sample/ directory, such as /opt/sample/bin/ for binaries and /opt/sample/man/ for manual pages.
Packages that encompass many different sub-packages, data files, extra fonts, clipart etc are also located in the /opt/ directory, giving that large package a way to organize itself. In this way, our sample package may have different tools that each go in their own sub-directories, such as /opt/sample/tool1/ and /opt/sample/tool2/, each of which can have their own bin/, man/, and other similar directories.
1.2.1.8. The /proc/ Directory
The /proc/ directory contains special
files that either extract information from or send information to the
kernel. Examples include system memory, cpu information, hardware
configuration etc.
Due to the great variety of data available within /proc/
and the many ways this directory can be used to communicate with the
kernel, an entire chapter has been devoted to the subject. For more
information, refer to Chapter 3, The proc File System.
1.2.1.9. The /sbin/ Directory
The /sbin/ directory stores executables used by the root user. The executables in /sbin/ are used at boot time, for system administration and to perform system recovery operations. Of this directory, the FHS says:
/sbin contains binaries essential for booting, restoring, recovering, and/or repairing the system in addition to the binaries in /bin. Programs executed after /usr/ is known to be mounted (when there are no problems) are generally placed into /usr/sbin. Locally-installed system administration programs should be placed into /usr/local/sbin.
At a minimum, the following programs should be in /sbin/:
arp, clock,
halt, init,
fsck.*, grub,
ifconfig, mingetty,
mkfs.*, mkswap,
reboot, route,
shutdown, swapoff,
swapon
1.2.1.10. The /srv/ Directory
The /srv/ directory contains
site-specific data served by your system running Red Hat Enterprise
Linux. This directory gives users the location of data files for a
particular service, such as FTP, WWW, or CVS. Data that only pertains to
a specific user should go in the /home/ directory.
1.2.1.11. The /sys/ Directory
The /sys/ directory utilizes the new sysfs
virtual file system specific to the 2.6 kernel. With the increased
support for hot plug hardware devices in the 2.6 kernel, the /sys/ directory contains information similarly held in /proc/, but displays a hierarchical view of specific device information in regards to hot plug devices.
1.2.1.12. The /usr/ Directory
The /usr/ directory is for files that can be shared across multiple machines. The /usr/
directory is often on its own partition and is mounted read-only. At a
minimum, the following directories should be subdirectories of /usr/:
/usr
|- bin/
|- etc/
|- games/
|- include/
|- kerberos/
|- lib/
|- libexec/
|- local/
|- sbin/
|- share/
|- src/
|- tmp -> ../var/tmp/
Under the /usr/ directory, the bin/ subdirectory contains executables, etc/ contains system-wide configuration files, games is for games, include/ contains C header files, kerberos/ contains binaries and other Kerberos-related files, and lib/ contains object files and libraries that are not designed to be directly utilized by users or shell scripts. The libexec/ directory contains small helper programs called by other programs, sbin/ is for system administration binaries (those that do not belong in the /sbin/ directory), share/ contains files that are not architecture-specific, src/ is for source code.
1.2.1.13. The /usr/local/ Directory
The FHS says:
The /usr/local hierarchy is for use by
the system administrator when installing software locally. It needs to
be safe from being overwritten when the system software is updated. It
may be used for programs and data that are shareable among a group of
hosts, but not found in /usr.
The /usr/local/ directory is similar in structure to the /usr/ directory. It has the following subdirectories, which are similar in purpose to those in the /usr/ directory:
/usr/local
|- bin/
|- etc/
|- games/
|- include/
|- lib/
|- libexec/
|- sbin/
|- share/
|- src/
In Red Hat Enterprise Linux, the intended use for the /usr/local/ directory is slightly different from that specified by the FHS. The FHS says that /usr/local/
should be where software that is to remain safe from system software
upgrades is stored. Since software upgrades can be performed safely with
RPM Package Manager ( RPM), it is not necessary to protect files by putting them
in /usr/local/. Instead, the /usr/local/ directory is used for software that is local to the machine.
For instance, if the /usr/ directory is
mounted as a read-only NFS share from a remote host, it is still
possible to install a package or program under the /usr/local/ directory.
1.2.1.14. The /var/ Directory
Since the FHS requires Linux to mount /usr/ as read-only, any programs that write log files or need spool/ or lock/ directories should write them to the /var/ directory. The FHS states /var/ is for:
...variable data files. This includes spool
directories and files, administrative and logging data, and transient
and temporary files.
Below are some of the directories found within the /var/ directory:
/var
|- account/
|- arpwatch/
|- cache/
|- crash/
|- db/
|- empty/
|- ftp/
|- gdm/
|- kerberos/
|- lib/
|- local/
|- lock/
|- log/
|- mail -> spool/mail/
|- mailman/
|- named/
|- nis/
|- opt/
|- preserve/
|- run/
+- spool/
|- at/
|- clientmqueue/
|- cron/
|- cups/
|- exim/
|- lpd/
|- mail/
|- mailman/
|- mqueue/
|- news/
|- postfix/
|- repackage/
|- rwho/
|- samba/
|- squid/
|- squirrelmail/
|- up2date/
|- uucp
|- uucppublic/
|- vbox/
|- tmp/
|- tux/
|- www/
Linux Filesystem Hierarchy
Version 0.65
Binh Nguyen
2004-07-30
This document outlines the set of requirements and guidelines for file
and directory placement under the Linux operating system according to
those of the FSSTND v2.3 final (January 29, 2004) and also its actual
implementation on an arbitrary system. It is meant to be accessible to
all members of the Linux community, be distribution independent and is
intended to discuss the impact of the FSSTND and how it has managed to
increase the efficiency of support interoperability of applications,
system administration tools, development tools, and scripts as well as
greater uniformity of documentation for these systems.
Copyright 2003 Binh Nguyen
Trademarks are owned by their owners.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.2; with no Invariant Sections, with no Front-Cover Texts,
and with no Back-Cover Texts. A copy of the license is included in
the section entitled "GNU Free Documentation License".
Chapter 1. Linux Filesystem Hierarchy
1.1. Foreward
When
migrating from another operating system such as Microsoft Windows to
another; one thing that will profoundly affect the end user greatly will
be the differences between the filesystems.
What are filesystems?
A filesystem is
the methods and data structures that an operating system uses to keep
track of files on a disk or partition; that is, the way the files are
organized on the disk. The word is also used to refer to a partition or
disk that is used to store the files or the type of the filesystem.
Thus, one might say I have two filesystems meaning one has two
partitions on which one stores files, or that one is using the extended
filesystem, meaning the type of the filesystem.
The difference between a disk or partition and the filesystem it
contains is important. A few programs (including, reasonably enough,
programs that create filesystems) operate directly on the raw sectors of
a disk
or partition; if there is an existing file system there it will be
destroyed or seriously corrupted. Most programs operate on a filesystem,
and therefore won't work on a partition that doesn't contain one (or
that contains one of the wrong type).
Before a partition or disk can be used as a filesystem, it needs to be initialized, and the bookkeeping
data structures need to be written to the disk. This process is called making a filesystem.
Most UNIX filesystem types have a similar general structure,
although the exact details vary quite a bit. The central concepts are superblock, inode, data block, directory block, and indirection block.
The superblock contains information about the filesystem as a whole,
such as its size (the exact information here depends on the filesystem).
An inode contains all information about a file, except its name. The
name is stored in the directory, together with the number of the inode. A
directory entry consists of a filename and the number of the inode
which represents the file. The inode contains the numbers of several
data blocks, which are used to store the data in the file. There is
space only for a few data block numbers in the inode, however, and if
more are needed, more space for pointers to the data blocks is allocated
dynamically. These dynamically allocated blocks are indirect blocks;
the name indicates that in order to find the data block, one has to find
its number in the indirect block first.
Like UNIX, Linux chooses to have a single hierarchical directory
structure. Everything starts from the root directory, represented by /,
and then expands into sub-directories instead of having so-called
'drives'. In
the Windows environment, one may put one's files almost anywhere: on C
drive, D drive, E drive etc. Such a file system is called a hierarchical
structure and is managed by the programs themselves (program
directories), not by the operating system. On the other hand, Linux
sorts directories descending from the root directory / according to
their importance to the boot process.
If you're wondering why Linux uses the frontslash / instead of
the backslash \ as in Windows it's because it's simply following the
UNIX tradition. Linux, like Unix also chooses to be case sensitive. What
this means is that the case, whether in capitals or not, of the
characters becomes very important. So this is not the same as THIS. This
feature accounts for a fairly large proportion of problems for new
users especially during file transfer operations whether it may be via
removable disk media such as floppy disk or over the wire by way of FTP.
The filesystem order is specific to the function of a
file and not to its program context (the majority of Linux filesystems
are 'Second Extended File Systems', short 'EXT2' (aka 'ext2fs' or
'extfs2') or are themselves subsets of this filesystem such as ext3 and
Reiserfs). It is within this filesystem
that the operating system determines into which directories programs
store their files.
If you install a program in Windows, it usually stores most of
its files in its own directory structure. A help file for instance may
be in C:\Program Files\[program name]\ or in C:\Program
Files\[program-name]\help or in C:\Program Files\[program
-name]\humpty\dumpty\doo. In Linux, programs put their documentation
into /usr/share/doc/[program-name], man(ual) pages into
/usr/share/man/man[1-9] and info pages into /usr/share/info.
They are merged into and with the system hierarchy.
As all Linux users know, unless you mount a partition or a
device, the system does not know of the existence of that partition or
device. This might not appear to be the easiest way to provide access to
your partitions or devices, however it offers the advantage of far
greater flexibility when compared to other operating systems. This kind
of layout, known as the unified filesystem, does offer several
advantages over the approach
that Windows uses. Let's take the example of the /usr directory. This
sub-directory of the root directory contains most of the system
executables. With the Linux filesystem, you can choose to mount it off
another partition or even off another machine over the network using an
innumerable set of protocols such as NFS (Sun), Coda
(CMU) or AFS (IBM). The underlying system will not and need not know the
difference. The presence of the /usr
directory is completely transparent. It appears to be a local directory
that is part of the local directory structure.
Compliance requires that:
+---------+-----------------+-------------+
| | shareable | unshareable |
+---------+-----------------+-------------+
|static | /usr | /etc |
| | /opt | /boot |
+---------+-----------------+-------------+
|variable | /var/mail | /var/run |
| | /var/spool/news | /var/lock |
+---------+-----------------+-------------+
"Shareable" files are defined as those that can be stored on one host and
used on others. "Unshareable" files are those that are not shareable. For
example, the files in user home directories are shareable whereas device
lock files are not. "Static" files include binaries, libraries,
documentation files and other files that do not change without system
administrator intervention. "Variable" files are defined as files that
are not static.
|
Another reason for this
unified filesystem is that Linux caches a lot of disk accesses using
system memory while it is running to accelerate these processes. It is
therefore vitally important that these buffers are flushed (get their
content written to disk), before the system closes down. Otherwise files
are left in an undetermined state which is of course a very bad thing.
Flushing is achieved by 'unmounting' the partitions during proper system
shutdown. In other words, don't switch your system off while it's
running! You may get away with it quite often, since the Linux
file system is very robust, but you may also wreak havoc upon important
files. Just hit ctrl-alt-del or use the proper commands (e.g. shutdown,
poweroff, init 0). This will shut down the system in a decent way which
will thus, guarantee the integrity of your files.
Many of us in
the Linux community have come to take for granted the existence of
excellent books and documents about Linux, an example being those
produced by the Linux Documentation Project. We are used to having
various packages taken from different sources such as Linux FTP sites
and distribution CD-ROMs integrate together smoothly. We have come to
accept that we all know where critical files like mount can be found on
any machine running Linux. We also take for granted CD-ROM based
distributions that can be run directly from the CD and which consume
only a small amount of physical hard disk or a RAM disk for some
variable files like /etc/passwd, etc. This has not always been the case.
During the adolescent years of Linux during the early to mid-90s
each distributor had his own favorite scheme for locating files in the
directory hierarchy. Unfortunately, this caused many problems. The Linux File System Structure
is a document, which was created to help end this anarchy. Often the
group, which creates this document or the document itself, is referred
to as the FSSTND. This is short for file system standard". This document
has helped to standardize the layout of file systems on Linux systems
everywhere. Since the original release of the standard, most
distributors have adopted it in whole or in part, much to
the benefit of all Linux users.
Since the first draft of the standard, the FSSTND project has
been coordinated by Daniel Quinlan and development of this standard has
been through consensus by a group of developers and Linux enthusiasts.
The FSSTND group set out to accomplish a number of specific goals. The
first goal was to solve a number of problems that existed with the
current distributions at the time. Back then, it was not possible to
have a shareable /usr
partition, there was no clear distinction between /bin and /usr/bin, it
was not possible to set up a diskless
workstation, and there was just general confusion about what files went
where. The second goal was to ensure the continuation of some reasonable
compatibility with the de-facto standards already in use in Linux and
other UNIX-like operating systems. Finally, the standard had to gain
widespread approval by the developers, distributors, and users within
the Linux community. Without such support, the standard would be
pointless, becoming just another way of laying out the file system.
Fortunately,
the FSSTND has succeeded though there are also some goals that the
FSSTND project did not set out to achieve. The FSSTND does not try to
emulate the scheme of any specific commercial UNIX operating system
(e.g. SunOS, AIX, etc.) Furthermore, for many of the files covered by
the FSSTND, the standard does not dictate whether the files should be
present, merely where the files should be if they are present. Finally,
for
most files, the FSSTND does not attempt to dictate the format of the
contents of the files. (There are some specific exceptions when several
different packages may need to know the file formats to work together
properly. For example, lock files that contain the process ID of the
process holding the lock.) The overall objective was to establish the
location where common files could be found, if they existed on a
particular machine. The FSSTND project began in early August 1993. Since
then, there have been a number of public revisions of this document.
The latest, v2.3 was released on January 29, 2004.
If you're
asking "What's the purpose of all this? Well, the answer depends on who
you are. If you are a
Linux user, and you don't administrate your own system then the FSSTND
ensures that you will be able to find programs where you'd expect them
to be if you've already had experience on another Linux machine. It also
ensures that any documentation you may have makes sense. Furthermore,
if you've already had some experience with Unix before, then the FSSTND
shouldn't be too different from what you're currently using, with a few
exceptions. Perhaps the most important thing is that the development of a
standard brings Linux to a level of maturity authors and commercial
application developers feel they can support.
If you administer
your own machine then you gain all the benefits of the FSSTND mentioned
above. You may also feel more secure in the ability of others to provide
support for you, should you have a problem. Furthermore, periodic
upgrades to your system are theoretically easier. Since there is an
agreed-upon standard for the locations of files, package maintainers can
provide instructions for upgrading that will not leave extra, older
files lying around your system inhabiting valuable disk space. The
FSSTND also means that there is more support from those providing source
code packages for you to compile and install yourself. The provider
knows, for example, where the executable for sed is to be found on a
Linux machine and can use that in his installation scripts or Makefiles.
If you run a large network, the FSSTND may ease many of your NFS
headaches, since it specifically addresses the problems which formerly
made shared implementations of /usr impractical. If you are a
distributor, then you will be affected most by the Linux FSSTND. You may
have to do a little extra work to make sure that your distribution is
FSSTND-compliant, but your users (and hence your business) will gain by
it. If your system is compliant, third party add-on packages (and
possibly your own) will integrate smoothly with your system. Your users
will, of course, gain all the benefits listed above, and many of your
support headaches will be eased.
You will benefit from all the discussion and thought that has been put
into the FSSTND and avoid many of the pitfalls involved in designing a
filesystem structure yourself. If you adhere to the FSSTND, you will
also be able to take advantage of various features that the FSSTND was
designed around. For example, the FSSTND makes "live" CD-ROMs containing
everything except some of the files in the / and /var directories
possible. If you write documentation for Linux, the FSSTND makes it much
easier to do so, which makes sense to the Linux community. You no
longer need to worry about the specific location of lock files on one
distribution versus another, nor are you forced to write documentation
that is only useful to the users of a specific distribution. The FSSTND
is at least partly responsible for the recent explosion of Linux books
being published.
If you are a developer, the existence of the
FSSTND greatly eases the possibility for potential problems. You can
know where important system binaries are found, so you can use them from
inside your programs or your shell scripts. Supporting users is also
greatly eased, since you don't have to worry about things like the
location of these binaries when resolving support issues. If you are the
developer of a program that needs to integrate with the rest of the
system, the FSSTND ensures that you can be certain of the steps to meet
this end. For example, applications such as kermit, which access the
serial ports, need to know they can achieve exclusive access to the TTY
device. The FSSTND specifies a common method of doing this so that all
compliant applications can work together. That way you can concentrate
on making more great software for Linux instead of worrying about how to
detect and deal with the differences in flavors of Linux. The
widespread acceptance of the FSSTND by the Linux community has been
crucial to the success of both the standard and operating system. Nearly
every modern distribution conforms to the Linux FSSTND. If your
implementation isn't at least partially FSSTND compliant, then it is
probably either very old or you built it yourself. The FSSTND itself
contains a list of some of the distributions that aim to conform to the
FSSTND. However, there are some distributions that are
known to cut some corners in their implementation of FSSTND.
By no means does this mean that the standard itself is complete. There are still unresolved issues such
as the organization of architecture-independent scripts and data files /usr/share. Up until now, the i386 has
been the primary platform for Linux, so the need for standardization of such files was non-existent.
The
rapid progress in porting Linux to other architectures (MC680x0, Alpha,
MIPS, PowerPC) suggests that this issue will soon need to be dealt
with. Another issue that is under some discussion is the creation of an
/opt directory as in SVR4. The goal for such a directory would be to
provide a location for large commercial
or third party packages to install themselves without worrying about the
requirements made by FSSTND for the other directory hierarchies. The
FSSTND provides the Linux community with an excellent reference document
and has proven to be an important factor in the maturation of Linux. As
Linux continues to evolve, so will the FSSTND.
Now, that we have seen how things should be,
let's take a look at the real world. As you will see, the
implementation of this concept on Linux isn't perfect and since Linux
has always attracted individualists who tend to be fairly opinionated,
it has been a bone of contention among users for instance which
directories certain files should be put into. With the arrival of
different distributions, anarchy has once again descended upon us. Some
distributions put mount directories for external media into the /
directory,
others into /mnt. Red Hat based distributions feature the /etc/sysconfig
sub-hierarchy for configuration files concerning input and network
devices. Other distributions do not have this directory at all and put
the appropriate files elsewhere or even use completely different
mechanisms to do the same thing. Some distributions put KDE into /opt/,
others into /usr.
But even within a given file system hierarchy, there are inconsistencies. For example, even though this
was never the intention of the XFree86 group, XFree86 does indeed have its own directory hierarchy.
These
problems don't manifest themselves as long as you compile programs
yourself. You can adapt configure scripts or Makefiles to your system's
configuration or to your preference. It's a different story if you
install pre-compiled packages like RPMs though. Often these are not
adaptable from one file system hierarchy to
another. What's worse: some RPMs might even create their own hierarchy.
If you, say, install a KDE RPM from the SuSE Linux distribution on your
Mandrake system, the binary will be put into /opt/kde2/bin. And thus it
won't work, because Mandrake expects it to be in /usr/bin. There are of
course ways to circumvent this problem but the current situation is
clearly untenable. Thus, all the leading Linux distributors have joined
the Linux Standard Base project, which is attempting to create a common
standard for Linux distributions. This isn't easy, since changing the
file system hierarchy means a lot of work for distributors so every
distributor tries to push a standard which will allow them to keep as
much of their own hierarchy as possible. The LSB will also encompass the
proposals made by the Filesystem Hierarchy Standard project (FHS,
former FSSTND).
1.2. The Root Directory
To comply with the FSSTND the following directories, or symbolic links
to directories, are required in /.
/bin Essential command binaries
/boot Static files of the boot loader
/dev Device files
/etc Host-specific system configuration
/lib Essential shared libraries and kernel modules
/media Mount point for removeable media
/mnt Mount point for mounting a filesystem temporarily
/opt Add-on application software packages
/sbin Essential system binaries
/srv Data for services provided by this system
/tmp Temporary files
/usr Secondary hierarchy
/var Variable data
|
The following directories, or symbolic links to directories,
must be in /, if the corresponding subsystem is installed:
/ -- the root directory
/home User home directories (optional)
/lib<qual> Alternate format essential shared libraries
(optional)
/root Home directory for the root user (optional)
|
Each directory listed above is described in detail
in separate subsections further on in this document.
The reference system will be based upon Debian 3.0r0 (Woody),
2.4.18 kernel configured to a Redhat kernel-2.4.18-i686.config file.
- Hardware
-
- Intel Celeron 766 Processor
- MSI MS-6309 V.2.0 Mainboard
- 512MB PQI PC133 SDRAM
- 16x Lite-On LTD-165H DVD-ROM
- 40x24x10 Sony CRX175A1 CD-RW
- NVIDIA RIVA 32MB TNT2 M64
- D-Link DFE-530TX 10/100 NIC
- Realtek RTL8029(AS) 10 NIC
- Lucent Mars2 Linmodem
- C-Media CMI8738 PCI Audio Device
- Miro DC-30 VIVO
- Aopen KF-45A Miditower Case
- Acer Accufeel Keyboard
- Genius Netscroll+ Mouse
- Compaq MV500 Presario Monitor
- Software
-
- Windows XP on /dev/hda1
- FreeBSD 4.2 on /dev/hda2
- Redhat 8.0 on /dev/hda5
- Debian 3.0r0 on /dev/hda6
- Mandrake 9.1 on /dev/hda7
- Swap partition on /dev/hda8
As we all know Linux file system starts with /, the root directory.
All other directories are 'children' of this directory. The partition
which the root file system resides on is mounted first during boot and
the system will not boot if it doesn't find it. On our reference system,
the root directory contains the following sub-directories:
bin/ dev/ home/ lost+found/ proc/ sbin/ usr/ cdrom/ opt/ vmlinuz
boot/ etc/ lib/ mnt/ root/ tmp/ var/ dvd/ floppy/ initrd/ /tftpboot
In days past it was also the home directory of 'root' but now he has
been given his own directory for reasons that will be explained further
on in this document.
1.3. /bin
Unlike /sbin, the bin directory contains several useful commands that
are of use to both the system administrator as well as non-privileged
users. It usually contains the shells like bash, csh, etc.... and
commonly used commands like cp, mv, rm, cat, ls. For this reason and in
contrast to /usr/bin, the binaries in this directory are considered to
be essential. The reason for this is that it contains essential system
programs that must be available even if only the partition containing /
is mounted. This situation may arise should you need to repair other
partitions but have no access to shared directories (ie. you are in
single user mode and hence have no network access). It also contains
programs which boot scripts may depend on.
Compliance to the FSSTND means that there are no subdirectories
in /bin and that the following commands, or symbolic links to commands,
are located there.
cat Utility to concatenate files to standard output
chgrp Utility to change file group ownership
chmod Utility to change file access permissions
chown Utility to change file owner and group
cp Utility to copy files and directories
date Utility to print or set the system data and time
dd Utility to convert and copy a file
df Utility to report filesystem disk space usage
dmesg Utility to print or control the kernel message buffer
echo Utility to display a line of text
false Utility to do nothing, unsuccessfully
hostname Utility to show or set the system's host name
kill Utility to send signals to processes
ln Utility to make links between files
login Utility to begin a session on the system
ls Utility to list directory contents
mkdir Utility to make directories
mknod Utility to make block or character special files
more Utility to page through text
mount Utility to mount a filesystem
mv Utility to move/rename files
ps Utility to report process status
pwd Utility to print name of current working directory
rm Utility to remove files or directories
rmdir Utility to remove empty directories
sed The `sed' stream editor
sh The Bourne command shell
stty Utility to change and print terminal line settings
su Utility to change user ID
sync Utility to flush filesystem buffers
true Utility to do nothing, successfully
umount Utility to unmount file systems
uname Utility to print system information
If /bin/sh is not a true Bourne shell, it must be a hard or symbolic link to
the real shell command.
The rationale behind this is because sh and bash mightn't necessarily behave
in the same manner. The use of a symbolic link also allows users to easily
see that /bin/sh is not a true Bourne shell.
The [ and test commands must be placed together in either /bin or /usr/bin.
The requirement for the [ and test commands to be included as binaries
(even if implemented internally by the shell) is shared with the POSIX.2
standard.
The following programs, or symbolic links to programs, must be in /bin if the
corresponding subsystem is installed:
csh The C shell (optional)
ed The `ed' editor (optional)
tar The tar archiving utility (optional)
cpio The cpio archiving utility (optional)
gzip The GNU compression utility (optional)
gunzip The GNU uncompression utility (optional)
zcat The GNU uncompression utility (optional)
netstat The network statistics utility (optional)
ping The ICMP network test utility (optional)
If the gunzip and zcat programs exist, they must be symbolic or hard links to
gzip. /bin/csh may be a symbolic link to /bin/tcsh or /usr/bin/tcsh.
The tar, gzip and cpio commands have been added to make restoration of a
system possible (provided that / is intact).
Conversely, if no restoration from the root partition is ever expected,
then these binaries might be omitted (e.g., a ROM chip root, mounting /usr
through NFS). If restoration of a system is planned through the network,
then ftp or tftp (along with everything necessary to get an ftp connection)
must be available on the root partition.
|
1.4. /boot
This directory contains everything required for the boot process
except for configuration files not needed at boot time (the most notable
of those being those that belong to the GRUB boot-loader) and the map
installer. Thus, the /boot directory stores data that is used before
the kernel begins executing user-mode programs. This may include redundant
(back-up) master boot records, sector/system map files, the kernel and
other important boot files and data that is not directly edited by hand.
Programs necessary to arrange for the boot loader to be able to boot a
file are placed in /sbin. Configuration files for boot loaders are placed
in /etc. The system kernel is located in either / or /boot (or as under
Debian in /boot but is actually a symbolically linked at / in accordance
with the FSSTND).
- /boot/boot.0300
- Backup
master boot record.
- /boot/boot.b
- This
is installed as the basic boot sector. In the case of most modern
distributions it is actually a symbolic link to one of four files
/boot/boot-bmp.b, /boot/boot-menu.b, /boot/boot-text.b, /boot/boot-compat.b
which allow a user to change the boot-up schema so that it utilises a splash
screen, a simple menu, a text based interface or a minimal boot loader to
ensure compatibility respectively. In each case re-installation of lilo is
necessary in order to complete the changes. To change the actual
'boot-logo' you can either use utilities such as fblogo or the more
refined bootsplash.
- /boot/chain.b
- Used
to boot non-Linux operating systems.
- /boot/config-kernel-version
- Installed
kernel configuration. This file is most useful when compiling kernels on
other systems or device modules. Below is a small sample of what the
contents of the file looks like.
CONFIG_X86=y
CONFIG_MICROCODE=m
CONFIG_X86_MSR=m
CONFIG_MATH_EMULATION=y
CONFIG_MTRR=y
CONFIG_MODULES=y
CONFIG_MODVERSIONS=y
CONFIG_SCSI_DEBUG=m
CONFIG_I2O=m
CONFIG_ARCNET_ETH=y
CONFIG_FMV18X=m
CONFIG_HPLAN_PLUS=m
CONFIG_ETH16I=m
CONFIG_NE2000=m
CONFIG_HISAX_HFC_PCI=y
CONFIG_ISDN_DRV_AVMB1_C4=m
CONFIG_USB_RIO500=m
CONFIG_QUOTA=y
CONFIG_AUTOFS_FS=m
CONFIG_ADFS_FS=m
CONFIG_AFFS_FS=m
CONFIG_HFS_FS=m
CONFIG_FAT_FS=y
CONFIG_MSDOS_FS=y
CONFIG_UMSDOS_FS=m
CONFIG_FBCON_VGA=m
CONFIG_FONT_8x8=y
CONFIG_FONT_8x16=y
CONFIG_SOUND=m
CONFIG_SOUND_CMPCI=m
CONFIG_AEDSP16=m
|
As you can see, it's rather
simplistic. The line begins with the configuration option and whether it's
configured as part of the kernel, as a module or not at all. Lines beginning
with a # symbol are comments and are not interpreted during processing.
- /boot/os2_d.b
- Used
to boot to the 0S/2 operating system.
- /boot/map
- Contains
the location of the kernel.
- /boot/vmlinuz, /boot/vmlinuz-kernel-version
- Normally the kernel or
symbolic link to the kernel.
- /boot/grub
- This
subdirectory contains the GRUB configuration files including boot-up images
and sounds. GRUB is the GNU GRand Unified Bootloader, a project which
intends to solve all bootup problems once and for all. One of the most
interesting features, is that you don't have to install a new partition
or kernel, you can change all parameters at boot time via the GRUB Console,
since it knows about the filesystems.
- /boot/grub/device.map
- Maps
devices in /dev to those used by grub. For example, (/dev/fd0) is
represented by /dev/fd0 and (hd0, 4) is referenced by /dev/hda5.
- /boot/grub/grub.conf,
/boot/grub/menu.lst
- Grub configuration file.
- /boot/grub/messages
- Grub
boot-up welcome message.
- /boot/grub/splash.xpm.gz
- Grub
boot-up background image.
1.5. /dev
/dev
is the location of special or device files. It is a very interesting
directory that highlights one important aspect of the Linux filesystem -
everything is a file or a directory. Look through this directory and
you should hopefully see hda1, hda2 etc.... which represent the various
partitions on the first master drive of the system. /dev/cdrom and
/dev/fd0 represent your CD-ROM drive and your floppy drive. This may
seem strange but it will make sense if you compare the characteristics
of files to that of your hardware. Both can be read from and written to.
Take /dev/dsp, for instance. This file represents your speaker device.
Any data written to this file will be re-directed to your speaker. If
you try 'cat /boot/vmlinuz > /dev/dsp' (on a properly configured
system) you should hear some sound on the speaker. That's the sound of
your kernel! A file sent to /dev/lp0 gets printed. Sending data to and
reading from /dev/ttyS0 will allow you to communicate with a device
attached there - for instance, your modem.
The majority of devices
are either block or character devices; however other types of devices
exist and can be created. In general, 'block devices' are devices that
store or hold data, 'character devices' can be thought of as devices
that transmit or transfer data. For example, diskette drives, hard
drives and CD-ROM drives are all block devices while serial ports, mice
and parallel printer ports are all character devices. There is a naming
scheme of sorts but in the vast majority of cases these are completely
illogical.
total 724
lrwxrwxrwx 1 root root 13 Sep 28 18:06 MAKEDEV -> /sbin/MAKEDEV
crw-rw---- 1 root audio 14, 14 Oct 7 16:26 admmidi0
crw-rw---- 1 root audio 14, 30 Oct 7 16:26 admmidi1
lrwxrwxrwx 1 root root 11 Oct 7 16:26 amidi -> /dev/amidi0
crw-rw---- 1 root audio 14, 13 Oct 7 16:26 amidi0
crw-rw---- 1 root audio 14, 29 Oct 7 16:26 amidi1
crw-rw---- 1 root audio 14, 11 Oct 7 16:26 amixer0
crw-rw---- 1 root audio 14, 27 Oct 7 16:26 amixer1
drwxr-xr-x 2 root root 4096 Sep 28 18:05 ataraid
lrwxrwxrwx 1 root root 11 Oct 7 16:26 audio -> /dev/audio0
crw-rw---- 1 root audio 14, 4 Oct 7 16:26 audio0
crw-rw---- 1 root audio 14, 20 Oct 7 16:26 audio1
crw-rw---- 1 root audio 14, 7 Mar 15 2002 audioctl
lrwxrwxrwx 1 root root 9 Oct 14 22:51 cdrom -> /dev/scd1
lrwxrwxrwx 1 root root 9 Oct 14 22:52 cdrom1 -> /dev/scd0
crw------- 1 root tty 5, 1 Jan 19 20:47 console
lrwxrwxrwx 1 root root 11 Sep 28 18:06 core -> /proc/kcore
crw-rw---- 1 root audio 14, 10 Oct 7 16:26 dmfm0
crw-rw---- 1 root audio 14, 26 Oct 7 16:26 dmfm1
crw-rw---- 1 root audio 14, 9 Oct 7 16:26 dmmidi0
crw-rw---- 1 root audio 14, 25 Oct 7 16:26 dmmidi1
lrwxrwxrwx 1 root root 9 Oct 7 16:26 dsp -> /dev/dsp0
crw-rw---- 1 root audio 14, 3 Oct 7 16:26 dsp0
crw-rw---- 1 root audio 14, 19 Oct 7 16:26 dsp1
crw--w---- 1 root video 29, 0 Mar 15 2002 fb0
crw--w---- 1 root video 29, 1 Mar 15 2002 fb0autodetect
crw--w---- 1 root video 29, 0 Mar 15 2002 fb0current
crw--w---- 1 root video 29, 32 Mar 15 2002 fb1
crw--w---- 1 root video 29, 33 Mar 15 2002 fb1autodetect
crw--w---- 1 root video 29, 32 Mar 15 2002 fb1current
lrwxrwxrwx 1 root root 13 Sep 28 18:05 fd -> /proc/self/fd
brw-rw---- 1 root floppy 2, 0 Mar 15 2002 fd0
brw-rw---- 1 root floppy 2, 1 Mar 15 2002 fd1
crw--w--w- 1 root root 1, 7 Sep 28 18:06 full
brw-rw---- 1 root disk 3, 0 Mar 15 2002 hda
brw-rw---- 1 root disk 3, 64 Mar 15 2002 hdb
brw-rw---- 1 root disk 22, 0 Mar 15 2002 hdc
brw-rw---- 1 root disk 22, 64 Mar 15 2002 hdd
drwxr-xr-x 2 root root 12288 Sep 28 18:05 ida
prw------- 1 root root 0 Jan 19 20:46 initctl
brw-rw---- 1 root disk 1, 250 Mar 15 2002 initrd
drwxr-xr-x 2 root root 4096 Sep 28 18:05 input
crw-rw---- 1 root dialout 45, 128 Mar 15 2002 ippp0
crw-rw---- 1 root dialout 45, 0 Mar 15 2002 isdn0
crw-rw---- 1 root dialout 45, 64 Mar 15 2002 isdnctrl0
crw-rw---- 1 root dialout 45, 255 Mar 15 2002 isdninfo
crw------- 1 root root 10, 4 Mar 15 2002 jbm
crw-r----- 1 root kmem 1, 2 Sep 28 18:06 kmem
brw-rw---- 1 root cdrom 24, 0 Mar 15 2002 lmscd
crw------- 1 root root 10, 0 Mar 15 2002 logibm
brw-rw---- 1 root disk 7, 0 Sep 28 18:06 loop0
brw-rw---- 1 root disk 7, 1 Sep 28 18:06 loop1
crw-rw---- 1 root lp 6, 0 Mar 15 2002 lp0
crw-rw---- 1 root lp 6, 1 Mar 15 2002 lp1
crw-rw---- 1 root lp 6, 2 Mar 15 2002 lp2
crw-r----- 1 root kmem 1, 1 Sep 28 18:06 mem
lrwxrwxrwx 1 root root 10 Oct 7 16:26 midi -> /dev/midi0
crw-rw---- 1 root audio 14, 2 Oct 7 16:26 midi0
crw-rw---- 1 root audio 14, 18 Oct 7 16:26 midi1
lrwxrwxrwx 1 root root 11 Oct 7 16:26 mixer -> /dev/mixer0
crw-rw-rw- 1 root root 14, 0 Nov 11 16:22 mixer0
crw-rw---- 1 root audio 14, 16 Oct 7 16:26 mixer1
lrwxrwxrwx 1 root root 11 Oct 7 06:50 modem -> /dev/ttyLT0
crw-rw---- 1 root audio 31, 0 Mar 15 2002 mpu401data
crw-rw---- 1 root audio 31, 1 Mar 15 2002 mpu401stat
crw-rw---- 1 root audio 14, 8 Oct 7 16:26 music
crw-rw-rw- 1 root root 1, 3 Sep 28 18:06 null
crw-rw-rw- 1 root root 195, 0 Jan 6 03:03 nvidia0
crw-rw-rw- 1 root root 195, 1 Jan 6 03:03 nvidia1
crw-rw-rw- 1 root root 195, 255 Jan 6 03:03 nvidiactl
crw-rw---- 1 root lp 6, 0 Mar 15 2002 par0
crw-rw---- 1 root lp 6, 1 Mar 15 2002 par1
crw-rw---- 1 root lp 6, 2 Mar 15 2002 par2
-rw-r--r-- 1 root root 665509 Oct 7 16:41 pcm
crw-r----- 1 root kmem 1, 4 Sep 28 18:06 port
crw-rw---- 1 root dip 108, 0 Sep 28 18:07 ppp
crw------- 1 root root 10, 1 Mar 15 2002 psaux
crw-rw-rw- 1 root root 1, 8 Sep 28 18:06 random
crw-rw---- 1 root root 10, 135 Mar 15 2002 rtc
brw-rw---- 1 root cdrom 11, 0 Mar 15 2002 scd0
brw-rw---- 1 root cdrom 11, 1 Mar 15 2002 scd1
brw-rw---- 1 root disk 8, 0 Mar 15 2002 sda
brw-rw---- 1 root disk 8, 1 Mar 15 2002 sda1
brw-rw---- 1 root disk 8, 2 Mar 15 2002 sda2
brw-rw---- 1 root disk 8, 3 Mar 15 2002 sda3
brw-rw---- 1 root disk 8, 4 Mar 15 2002 sda4
brw-rw---- 1 root disk 8, 16 Mar 15 2002 sdb
brw-rw---- 1 root disk 8, 17 Mar 15 2002 sdb1
brw-rw---- 1 root disk 8, 18 Mar 15 2002 sdb2
brw-rw---- 1 root disk 8, 19 Mar 15 2002 sdb3
brw-rw---- 1 root disk 8, 20 Mar 15 2002 sdb4
crw-rw---- 1 root audio 14, 1 Oct 7 16:26 sequencer
lrwxrwxrwx 1 root root 10 Oct 7 16:26 sequencer2 -> /dev/music
lrwxrwxrwx 1 root root 4 Sep 28 18:05 stderr -> fd/2
lrwxrwxrwx 1 root root 4 Sep 28 18:05 stdin -> fd/0
lrwxrwxrwx 1 root root 4 Sep 28 18:05 stdout -> fd/1
crw-rw-rw- 1 root tty 5, 0 Sep 28 18:06 tty
crw------- 1 root root 4, 0 Sep 28 18:06 tty0
crw------- 1 root root 4, 1 Jan 19 14:59 tty1
crw-rw---- 1 root dialout 62, 64 Oct 7 06:50 ttyLT0
crw-rw---- 1 root dialout 4, 64 Mar 15 2002 ttyS0
crw-rw---- 1 root dialout 4, 65 Mar 15 2002 ttyS1
crw-rw---- 1 root dialout 4, 66 Mar 15 2002 ttyS2
crw-rw---- 1 root dialout 4, 67 Mar 15 2002 ttyS3
crw-rw---- 1 root dialout 188, 0 Mar 15 2002 ttyUSB0
crw-rw---- 1 root dialout 188, 1 Mar 15 2002 ttyUSB1
cr--r--r-- 1 root root 1, 9 Jan 19 20:46 urandom
drwxr-xr-x 2 root root 4096 Sep 28 18:05 usb
prw-r----- 1 root adm 0 Jan 19 14:58 xconsole
crw-rw-rw- 1 root root 1, 5 Sep 28 18:06 zero
|
Some common device files as well as their equivalent counterparts under Windows that you may wish to remember are:
- /dev/ttyS0 (First communications port, COM1)
-
First serial port (mice, modems).
- /dev/psaux (PS/2)
-
PS/2 mouse connection (mice, keyboards).
- /dev/lp0 (First printer port, LPT1)
-
First parallel port (printers, scanners, etc).
- /dev/dsp (First audio device)
-
The name DSP comes from the term digital signal processor, a specialized
processor chip optimized for digital signal analysis. Sound cards may
use a dedicated DSP chip, or may implement the functions with a number
of discrete devices. Other terms that may be used for this device are
digitized voice and PCM.
- /dev/usb (USB Devices)
-
This subdirectory contains most of the USB device nodes. Device name
allocations are fairly simplistic so no elaboration is be necessary.
- /dev/sda (C:\, SCSI device)
-
First SCSI device (HDD, Memory Sticks, external mass storage devices such as CD-ROM drives on laptops, etc).
- /dev/scd (D:\, SCSI CD-ROM device)
-
First SCSI CD-ROM device.
- /dev/js0 (Standard gameport joystick)
-
First joystick device.
Devices
are defined by type, such as 'block' or 'character', and 'major' and
'minor' number. The major number is used to categorize a device and the
minor number is used to identify a specific device type. For example,
all IDE device connected to the primary controller have a major number
of 3. Master and slave devices, as well as individual partitions are
further defined by the use of minor numbers. These are the two numbers
precede the date in the following display:
# ls -l /dev/hd*
brw-rw---- 1 root disk 3, 0 Mar 15 2002 /dev/hda
brw-rw---- 1 root disk 3, 1 Mar 15 2002 /dev/hda1
brw-rw---- 1 root disk 3, 10 Mar 15 2002 /dev/hda10
brw-rw---- 1 root disk 3, 11 Mar 15 2002 /dev/hda11
brw-rw---- 1 root disk 3, 12 Mar 15 2002 /dev/hda12
brw-rw---- 1 root disk 3, 13 Mar 15 2002 /dev/hda13
brw-rw---- 1 root disk 3, 14 Mar 15 2002 /dev/hda14
brw-rw---- 1 root disk 3, 15 Mar 15 2002 /dev/hda15
brw-rw---- 1 root disk 3, 16 Mar 15 2002 /dev/hda16
brw-rw---- 1 root disk 3, 17 Mar 15 2002 /dev/hda17
brw-rw---- 1 root disk 3, 18 Mar 15 2002 /dev/hda18
brw-rw---- 1 root disk 3, 19 Mar 15 2002 /dev/hda19
brw-rw---- 1 root disk 3, 2 Mar 15 2002 /dev/hda2
brw-rw---- 1 root disk 3, 20 Mar 15 2002 /dev/hda20
brw-rw---- 1 root disk 3, 3 Mar 15 2002 /dev/hda3
brw-rw---- 1 root disk 3, 4 Mar 15 2002 /dev/hda4
brw-rw---- 1 root disk 3, 5 Mar 15 2002 /dev/hda5
brw-rw---- 1 root disk 3, 6 Mar 15 2002 /dev/hda6
brw-rw---- 1 root disk 3, 7 Mar 15 2002 /dev/hda7
brw-rw---- 1 root disk 3, 8 Mar 15 2002 /dev/hda8
brw-rw---- 1 root disk 3, 9 Mar 15 2002 /dev/hda9
brw-rw---- 1 root disk 3, 64 Mar 15 2002 /dev/hdb
brw-rw---- 1 root disk 3, 65 Mar 15 2002 /dev/hdb1
brw-rw---- 1 root disk 3, 74 Mar 15 2002 /dev/hdb10
brw-rw---- 1 root disk 3, 75 Mar 15 2002 /dev/hdb11
brw-rw---- 1 root disk 3, 76 Mar 15 2002 /dev/hdb12
brw-rw---- 1 root disk 3, 77 Mar 15 2002 /dev/hdb13
brw-rw---- 1 root disk 3, 78 Mar 15 2002 /dev/hdb14
brw-rw---- 1 root disk 3, 79 Mar 15 2002 /dev/hdb15
brw-rw---- 1 root disk 3, 80 Mar 15 2002 /dev/hdb16
brw-rw---- 1 root disk 3, 81 Mar 15 2002 /dev/hdb17
brw-rw---- 1 root disk 3, 82 Mar 15 2002 /dev/hdb18
brw-rw---- 1 root disk 3, 83 Mar 15 2002 /dev/hdb19
brw-rw---- 1 root disk 3, 66 Mar 15 2002 /dev/hdb2
brw-rw---- 1 root disk 3, 84 Mar 15 2002 /dev/hdb20
brw-rw---- 1 root disk 3, 67 Mar 15 2002 /dev/hdb3
brw-rw---- 1 root disk 3, 68 Mar 15 2002 /dev/hdb4
brw-rw---- 1 root disk 3, 69 Mar 15 2002 /dev/hdb5
brw-rw---- 1 root disk 3, 70 Mar 15 2002 /dev/hdb6
brw-rw---- 1 root disk 3, 71 Mar 15 2002 /dev/hdb7
brw-rw---- 1 root disk 3, 72 Mar 15 2002 /dev/hdb8
brw-rw---- 1 root disk 3, 73 Mar 15 2002 /dev/hdb9
brw-rw---- 1 root disk 22, 0 Mar 15 2002 /dev/hdc
brw-rw---- 1 root disk 22, 64 Mar 15 2002 /dev/hdd
|
The major number for both hda and hdb devices is 3. Of course,
the minor number changes for each specific partition. The definition of
each major number category can be examined by looking at the contents of
the /usr/src/linux/include/linux/major.h file. The devices.txt also
documents major and minor numbers. It is located in the
/usr/src/linux/Documentation directory. This file defines the major
numbers. Almost all files devices are created by default at the install
time. However, you can always create a device using the mknod command or
the MAKEDEV script which is located in the /dev directory itself.
Devices can be created with this utility by supplying the device to be
created, the device type (block or character) and the major and minor
numbers. For example, let's say you have accidentally deleted /dev/ttyS0
(COM1 under Windows), it can be recreated using the following command
# mknod ttyS0 c 4 64
For those of us who are rather lazy you can simply run the MAKEDEV script as such
# MAKEDEV *
which will create all devices known.
If is possible that /dev may also contain a MAKEDEV.local for the creation of any local device files.
In
general and as required by the FSSTND, MAKEDEV will have provisions for
creating any device that may be found on the system, not just those
that a particular implementation installs.
For those of you who
are wondering why Linux is using such a primitive system to reference
devices its because we haven't been able to devise a sufficiently
sophisticated mechanism which provides enough advantages over the
current system in order to achieve widespread adoption.
To date
(as of kernel version 2.4), the best attempt has been made by Richard
Gooch of the CSIRO. It's called devfsd and has been a part of the kernel
for a number of years now. It has been sanctioned by the kernel
developers and Linus himself and details of its implementation can be
found at /usr/src/linux/Documentation/filesystems/devfs/README. Below is
an excerpt from this document.
Devfs is an alternative to "real"
character and block special devices on your root filesystem. Kernel
device drivers can register devices by name rather than major and minor
numbers. These devices will appear in devfs automatically, with whatever
default ownership and protection the driver specified. A daemon
(devfsd) can be used to override these defaults. Devfs has been in the
kernel since 2.3.46.
NOTE that devfs is entirely optional. If you
prefer the old disc-based device nodes, then simply leave
CONFIG_DEVFS_FS=n (the default). In this case, nothing will change.
ALSO NOTE that if you do enable devfs, the defaults are such that full
compatibility is maintained with the old devices names.
There are
two aspects to devfs: one is the underlying device namespace, which is a
namespace just like any mounted filesystem. The other aspect is the
filesystem code which provides a view of the device namespace. The
reason I make a distinction is because devfs can be mounted many times,
with each mount showing the same device namespace. Changes made are
global to all mounted devfs filesystems. Also, because the devfs
namespace exists without any devfs mounts, you can easily mount the root
filesystem by referring to an entry in the devfs namespace.
The
cost of devfs is a small increase in kernel code size and memory usage.
About 7 pages of code (some of that in __init sections) and 72 bytes for
each entry in the namespace. A modest system has only a couple of
hundred device entries, so this costs a few more pages. Compare this
with the suggestion to put /dev on a ramdisc.
On a typical
machine, the cost is under 0.2 percent. On a modest system with 64
MBytes of RAM, the cost is under 0.1 percent. The accusations of
"bloatware" levelled at devfs are not justified.
As of kernel
version 2.6, devfs has been marked obsolete and has now been replaced by
udev. A system very similar (at least from a the end user's point of
view) to devfs but which works entirely in userspace. An overview of
udev can be found at http://www.kroah.com/linux/talks/ols_2003_udev_paper/Reprint-Kroah-Hartman-OLS2003.pdf
1.6. /etc
This is the nerve center of your system, it contains all system
related configuration files in here or in its sub-directories. A
"configuration file" is defined as a local file used to control
the operation of a program; it must be static and cannot be an executable binary.
For this reason, it's a good idea to backup this directory regularly. It will
definitely save you a lot of re-configuration later if you re-install or
lose your current installation. Normally, no binaries should be or are
located here.
- /etc/X11/
- This
directory tree contains all the configuration files for the X Window System.
Users should note that many of the files located in this directory are
actually symbolic links to the /usr/X11R6 directory tree. Thus, the
presence of these files in these locations can not be certain.
- /etc/X11/XF86Config,
/etc/X11/XF86Config-4
- The 'X' configuration
file. Most modern distributions possess hardware autodetection systems that
enable automatic creation of a valid file. Should autodetection fail a
configuration file can also be created manually provided that you have
sufficient knowledge about your system. It would be considered prudent not
to attempt to type out a file from beginning to end. Rather, use common
configuration utilities such as xf86config, XF86Setup and xf86cfg to create
a workable template. Then, using suitable documentation commence
optimization through intuition and/or trial and error. Options that can be
configured via this file include X modules to be loaded on startup,
keyboard, mouse, monitor and graphic chipset type. Often, commercial
distributions will include their own X configuration utilities such as
XDrake on Mandrake and also Xconfiguration on Redhat. Below is a sample X
configuration file from the reference system
### BEGIN DEBCONF SECTION
# XF86Config-4 (XFree86 server configuration file) generated by dexconf, the
# Debian X Configuration tool, using values from the debconf database.
#
# Edit this file with caution, and see the XF86Config-4 manual page.
# (Type "man XF86Config-4" at the shell prompt.)
#
# If you want your changes to this file preserved by dexconf, only
# make changes
# before the "### BEGIN DEBCONF SECTION" line above, and/or after the
# "### END DEBCONF SECTION" line below.
#
# To change things within the debconf section, run the command:
# dpkg-reconfigure xserver-xfree86
# as root. Also see "How do I add custom sections to a dexconf-
# generated
# XF86Config or XF86Config-4 file?" in /usr/share/doc/xfree86-
# common/FAQ.gz.
Section "Files"
FontPath "unix/:7100"
# local font server
# if the local font server has problems,
# we can fall back on these
FontPath "/usr/lib/X11/fonts/misc"
FontPath "/usr/lib/X11/fonts/cyrillic"
FontPath "/usr/lib/X11/fonts/100dpi/:unscaled"
FontPath "/usr/lib/X11/fonts/75dpi/:unscaled"
FontPath "/usr/lib/X11/fonts/Type1"
FontPath "/usr/lib/X11/fonts/Speedo"
FontPath "/usr/lib/X11/fonts/100dpi"
FontPath "/usr/lib/X11/fonts/75dpi"
EndSection
Section "Module"
Load "GLcore"
Load "bitmap"
Load "dbe"
Load "ddc"
Load "dri"
Load "extmod"
Load "freetype"
Load "glx"
Load "int10"
Load "pex5"
Load "record"
Load "speedo"
Load "type1"
Load "vbe"
Load "xie"
EndSection
Section "InputDevice"
Identifier "Generic Keyboard"
Driver "keyboard"
Option "CoreKeyboard"
Option "XkbRules" "xfree86"
Option "XkbModel" "pc104"
Option "XkbLayout" "us"
EndSection
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/psaux"
Option "Protocol" "NetMousePS/2"
Option "Emulate3Buttons" "true"
Option "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
Identifier "Generic Mouse"
Driver "mouse"
Option "SendCoreEvents" "true"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "Emulate3Buttons" "true"
Option "ZAxisMapping" "4 5"
EndSection
Section "Device"
Identifier "Generic Video Card"
Driver "nv"
# Option "UseFBDev" "true"
Option "UseFBDev" "false"
EndSection
Section "Monitor"
Identifier "Generic Monitor"
HorizSync 30-38
VertRefresh 43-95
Option "DPMS"
EndSection
Section "Screen"
Identifier "Default Screen"
Device "Generic Video Card"
Monitor "Generic Monitor"
DefaultDepth 16
SubSection "Display"
Depth 1
Modes "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 4
Modes "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 8
Modes "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 15
Modes "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 16
Modes "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 24
Modes "800x600" "640x480"
EndSubSection
EndSection
Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
InputDevice "Generic Mouse"
EndSection
Section "DRI"
Mode 0666
EndSection
### END DEBCONF SECTION
|
As you can see, the layout of the file is quite simple
and tends to be quite standard across most distributions. At the top are the
locations of the various font files for X (note - X will not start if you do
not specify a valid font), next is the "Modules" section. It details
what modules are to be loaded upon startup. The most well known extensions
are probably GLX (required for 3D rendering of graphics and games) and
Xinerama which allows users to expand their desktop over several monitors.
Next are the various "Device" sections which describe the type of
hardware you have. Improper configuration of these subsections can lead to
heartache and trauma with seemingly misplaced keys, bewitched mice and also
constant flashing as X attempts to restart in a sometimes never ending loop.
In most cases when all else fails the vesa driver seems to be able to
initialise most modern video cards. In the "Screen" section it is
possible to alter the default startup resolution and depth. Quite often it
is possible to alter these attributes on the fly by using the alt-ctrl-+ or
alt-ctrl- set of keystrokes. Lastly are the "ServerLayout" and
"DRI" sections. Users will almost never touch the "DRI"
section and only those who wish to utilise the Xinerama extensions of X will
require having to change any of the ServerLayout options.
- /etc/X11/Xmodmap
- In
general your default keyboard mapping comes from your X server setup. If
this setup is insufficient and you are unwilling to go through the process
of reconfiguration and/or you are not the superuser you'll need to use
the xmodmap program. This is the utility's global configuration file.
- /etc/X11/xkb/
- The
various symbols, types, geometries of keymaps that the X server supports can
be found in this directory tree.
- /etc/X11/lbxproxy/
- Low
Bandwidth X (LBX) proxy server configuration files. Applications that would
like to take advantage of the Low Bandwidth extension to X (LBX) must make
their connections to an lbxproxy. These applications need know nothing about
LBX, they simply connect to the lbxproxy as if it were a regular X server.
The lbxproxy accepts client connections, multiplexes them over a single
connection to the X server, and performs various optimizations on the X
protocol to make it faster over low bandwidth and/or high latency
connections. It should be noted that such compression will not increase the
pace of rendering all that much. Its primary purpose is to reduce network
load and thus increase overall network latency. A competing project called
DXPC (Differential X Protocol Compression) has been found to be more
efficient at this task. Studies have shown though that in almost all cases
ssh tunneling of X will produce far better results than through any of
these specialised pieces of software.
- /etc/X11/proxymngr/
- X
proxy services manager initialisation files. proxymngr is responsible for
resolving requests from xfindproxy (in the xbase-clients package) and other
similar clients, starting new proxies when appropriate, and keeping track of
all the available proxy services.
- /etc/X11/xdm/
- X
display manager configuration files. xdm manages a collection of X servers,
which may be on the local host or remote machines. It provides services
similar to those provided by init, getty, and login on character-based
terminals: prompting for login name and password, authenticating the user,
and running a session. xdm supports XDMCP (X Display Manager Control
Protocol) and can also be used to run a chooser process which presents the
user with a menu of possible hosts that offer XDMCP display management. If
the xutils package is installed, xdm can use the sessreg utility to register
login sessions to the system utmp file; this, however, is not necessary for
xdm to function.
- /etc/X11/xdm/xdm-config
- This
is the master 'xdm' configuration file. It determines where all
other 'xdm' configuration files will be located. It is almost
certain to be left undisturbed.
- /etc/X11/gdm/
- GNOME
Display Manager configuration files. gdm provides the equivalent of a
"login:" prompt for X displays- it pops up a login window and starts
an X session. It provides all the functionality of xdm, including XDMCP
support for managing remote displays. The greeting window is written using
the GNOME libraries and hence looks like a GNOME application- even to the
extent of supporting themes! By default, the greeter is run as an
unprivileged user for security.
- /etc/X11/gdm/gdm.conf
- This
is the primary configuration file for GDM. Through it, users can specify
whether they would like their system to automatically login as a certain
user, background startup image and also if they would like to run their
machine as somewhat of a terminal server by using the XDMCP protocol.
- /etc/X11/fonts
- Home
of xfs fonts.
- /etc/X11/fs/
- X
font server configuration files. xfs is a daemon that listens on a network
port and serves X fonts to X servers (and thus to X clients). All X servers
have the ability to serve locally installed fonts for themselves, but xfs
makes it possible to offload that job from the X server, and/or have a
central repository of fonts on a networked machine running xfs so that all
the machines running X servers on a network do not require their own set of
fonts. xfs may also be invoked by users to, for instance, make available X
fonts in user accounts that are not available to the X server or to an
already running system xfs.
- /etc/X11/fs/config
- This
is the 'xfs' initialisation file. It specifies the number of clients
that are allowed to connect to the 'xfs' server at any one time, the
location of log files, default resolution, the location of the fonts, etc.
# font server configuration file
# $Xorg: config.cpp,v 1.3 2000/08/17 19:54:19 cpqbld Exp $
# allow a maximum of 10 clients to connect to this font server
client-limit = 10
# when a font server reaches its limit, start up a new one
clone-self = on
# log messages to /var/log/xfs.log (if syslog is not used)
error-file = /var/log/xfs.log
# log errors using syslog
use-syslog = on
# turn off TCP port listening (Unix domain connections are still permitted)
no-listen = tcp
# paths to search for fonts
catalogue = /usr/lib/X11/fonts/misc/,/usr/lib/X11/fonts/cyrillic/,
/usr/lib/X11/fonts/100dpi/:unscaled,/usr/lib/X11/fonts/75dpi/:unscaled,
/usr/lib/X11/fonts/Type1/,/usr/lib/X11/fonts/CID,
/usr/lib/X11/fonts/Speedo/,/usr/lib/X11/fonts/100dpi/,
/usr/lib/X11/fonts/75dpi/
# in decipoints
default-point-size = 120
# x1,y1,x2,y2,...
default-resolutions = 100,100,75,75
# font cache control, specified in kB
cache-hi-mark = 2048
cache-low-mark = 1433
cache-balance = 70
|
- /etc/X11/twm
- Home
of configuration files for twm. The original Tabbed Window Manager.
- /etc/X11/xinit/
- xinit
configuration files. 'xinit' is a configuration method of starting
up an X session that is designed to used as part of a script. Normally, this
is used at larger sites as part of a tailored login process.
- /etc/X11/xinit/xinitrc
- Global
xinitrc file, used by all X sessions started by xinit (startx). Its
usage is of course overridden by a .xinitrc file located in the home
directory of a user.
- /etc/adduser.conf
- 'adduser'
configuration. The adduser command can create new users, groups and add
existing users to existing groups. Adding users with adduser is much easier
than adding them by hand. Adduser will choose appropriate UID and GID
values, create a home directory, copy skeletal user configuration from
/etc/skel, allow you to set an initial password and the GECOS field.
Optionally a custom script can be executed after this commands. See
adduser(8) and adduser.conf(5) for full documentation.
- /etc/adjtime
- Has
parameters to help adjust the software (kernel) time so that it matches the
RTC.
- /etc/aliases
- This
is the aliases file - it says who gets mail for whom. It was originally
generated by `eximconfig', part of the exim package distributed with
Debian, but it may edited by the mail system administrator. See exim info
section for details of the things that can be configured here. An aliases
database file (aliases.db) is built from the entries in the aliases files by
the newaliases utility.
- /etc/alternatives
- It
is possible for several programs fulfilling the same or similar functions to
be installed on a single system at the same time. For example, many systems
have several text editors installed at once. This gives choice to the users
of a system, allowing each to use a different editor, if desired, but makes
it difficult for a program to make a good choice of editor to invoke if the
user has not specified a particular preference.
The alternatives
system aims to solve this problem. A generic name in the filesystem is
shared by all files providing interchangeable functionality. The
alternatives system and the system administrator together determine which
actual file is referenced by this generic name. For example, if the text
editors ed(1) and nvi(1) are both installed on the system, the alternatives
system will cause the generic name /usr/bin/editor to refer to /usr/bin/nvi
by default. The system administrator can override this and cause it to refer
to /usr/bin/ed instead, and the alternatives system will not alter this
setting until explicitly requested to do so.
The generic name is
not a direct symbolic link to the selected alternative. Instead, it is a
symbolic link to a name in the alternatives directory, which in turn is a
symbolic link to the actual file referenced. This is done so that the system
administrator's changes can be confined within the /etc directory.
- /etc/apt
-
This is Debian's next generation front-end for the dpkg package manager.
It provides the apt-get utility and APT dselect method that provides a
simpler, safer way to install and upgrade packages. APT features
complete installation ordering, multiple source capability and several
other unique features, see the Users Guide in
/usr/share/doc/apt/guide.text.gz
- /etc/apt/sources.list
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-7 (20020718)]/
unstable contrib main non-US/contrib non-US/main
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-6 (20020718)]/
unstable contrib main non-US/contrib non-US/main
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-5 (20020718)]/
unstable contrib main non-US/contrib non-US/main
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-4 (20020718)]/
unstable contrib main non-US/contrib non-US/main
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-3 (20020718)]/
unstable contrib main non-US/contrib non-US/main
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-2 (20020718)]/
unstable contrib main non-US/contrib non-US/main
deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-1 (20020718)]/
unstable contrib main non-US/contrib non-US/main
# deb http://security.debian.org/ stable/updates main
|
Contains a list of apt-sources from which packages may be installed via APT.
- /etc/asound.conf
- ALSA
(Advanced Linux Sound Architecture) configuration file. It is normally
created via alsactl or other third-party sound configuration utilities that
may be specific to a distribution such as sndconfig from Redhat.
- /etc/at.deny
- Users
denied access to the at daemon. The 'at' command allows user to
execute programs at an arbitrary time.
- /etc/autoconf
- Configuration
files for autoconf. 'autoconf' creates scripts to configure source
code packages using templates. To create configure from configure.in, run
the autoconf program with no arguments. autoconf processes configure.ac with
the m4 macro processor, using the Autoconf macros. If you give autoconf an
argument, it reads that file instead of configure.ac and writes the
configuration script to the standard output instead of to configure. If you
give autoconf the argument -, it reads the standard input instead of
configure.ac and writes the configuration script on the standard output.
The
Autoconf macros are defined in several files. Some of the files are
distributed with Autoconf; autoconf reads them first. Then it looks for the
optional file acsite.m4 in the directory that contains the distributed
Autoconf macro files, and for the optional file aclocal.m4 in the current
directory. Those files can contain your site's or the package's own
Autoconf macro definitions. If a macro is defined in more than one of the
files that autoconf reads, the last definition it reads overrides the
earlier ones.
- /etc/bash.bashrc
- System
wide functions and aliases' file for interactive bash shells.
- /etc/bash_completion
- Programmable
completion functions for bash 2.05a.
- /etc/chatscripts/provider
- This
is the chat script used to dial out to your default service provider.
- /etc/cron.d,
/etc/cron.daily, /etc/cron.weekly, /etc/cron.monthly
- These
directories contain scripts to be executed on a regular basis by the cron
daemon.
- /etc/crontab
- 'cron'
configuration file. This file is for the cron table to setup the automatic
running of system routines. A cron table can also be established for
individual users. The location of these user cron table files will be
explained later on.
# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file.
# This file also has a username field, that none of the other crontabs do.
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# m h dom mon dow user command
25 6 * * * root test -e /usr/sbin/anacron || run-parts --report /etc/cron.daily
47 6 * * 7 root test -e /usr/sbin/anacron || run-parts --report /etc/cron.weekly
52 6 1 * * root test -e /usr/sbin/anacron || run-parts --report /etc/cron.monthly
#
|
- /etc/csh.login
- System-wide
.login file for csh(1). This file is sourced on all invocations of the
shell. It contains commands that are to be executed upon login and sometimes
aliases also.
- /etc/csh.logout
- System-wide
.logout file for csh(1). This file is sourced on all invocations of the
shell. It contains commands that are to be executed upon logout.
- /etc/csh.cshrc
- System-wide
.cshrc file for csh(1). This file is sourced on all invocations of the
shell. This file should contain commands to set the command search path,
plus other important environment variables. This file should not contain
commands that produce output or assume the shell is attached to a tty.
- /etc/cups
- Configuration
files for the Common UNIX Printing System (CUPS). Files here are used to
define client-specific parameters, such as the default server or default
encryption settings.
- /etc/deluser.conf
- 'deluser'
configuration files. The deluser command can remove users and groups and
remove users from a given group. Deluser can optionally remove and backup
the user's home directory and mail spool or all files on the system
owned by him. Optionally a custom script can also be executed after each of
the commands.
- /etc/devfs
-
This daemon sets up the /dev filesystem for use. It creates required
symbolic links in /dev and also creates (if so configured, as is the
default) symbolic links to the "old" names for devices.
- /etc/devfs/conf.d/
- 'devfsd'
configuration files. This daemon sets up the /dev filesystem for use. It
creates required symbolic links in /dev and also creates (if so configured,
as is the default) symbolic links to the "old" names for devices.
- /etc/dhclient.conf,
/etc/dhclient-script
- 'dhclient' configuration
file and 'dhclient' script files respectively. It configures your
system so that it may act as a client on a DHCP based network. It is
essential to connect to the Internet nowadays.
- /etc/dict.conf
# /etc/dict.conf Written by Bob Hilliard <hilliard@debian.org>
# 1998/03/20. Last revised Sun, 22 Nov 1998 18:10:04 -0500 This is
# the configuration file for /usr/bin/dict. In most cases only the
# server keyword need be specified.
# This default configuration will try to access a dictd server on
# the local host, failing that, it will try the public server. In
# many cases this will be slow, so you should comment out the line
# for the server that you don't want to use. To use any other
# server, enter its IP address in place of "dict.org".
# Refer to the dict manpage (man dict) for other options that could
# be inserted in here.
server localhost
server dict.org
|
dict is a client for the Dictionary Server Protocol (DICT), a TCP transaction based
query/response protocol that provides access to dictionary definitions from a set of natural
language dictionary databases.
- /etc/dosemu.conf
- Configuration
file for the Linux DOS Emulator. DOSEMU is a PC Emulator application that
allows Linux to run a DOS operating system in a virtual x86 machine. This
allows you to run many DOS applications. It includes the FreeDOS kernel,
color text and full keyboard emulation (via hotkeys) via terminal,
built-in X support, IBM character set font, graphics capability
at the console with most compatible video cards, DPMI support so you can
run DOOM, CDROM support, builtin IPX and pktdrvr support. Note -
'dosemu' is simply a ported version of Corel's own PC-DOS.
- /etc/email-addresses
- Part
of the exim package. This file contains email addresses to use for outgoing
mail. Any local part not in here will be qualified by the system domain as
normal. It should contain lines of the form:
user: someone@isp.com
otheruser: someoneelse@anotherisp.com
|
Exim is an MTA that is considered to be rather easier to configure than smail or
sendmail. It is a drop-in replacement for sendmail, mailq and rsmtp.
Advanced features include the ability to reject connections from known spam
sites, and an extremely efficient queue processing algorithm.
- /etc/esound.conf
- ESD
configuration files. The Enlightened sound daemon is designed to mix
together several digitized audio streams for playback by a single device.
Like nasd, artsd and rplay it also has the capability to play sounds
remotely.
- /etc/exports
- The
control list of systems who want to access the system via NFS, a the list of
directories that you would like to share and the permissions allocated on
each share.
# /etc/exports: the access control list for filesystems which may be
# exported to NFS clients. See exports(5).
## LTS-begin ##
#
# The lines between the 'LTS-begin' and the 'LTS-end' were added
# on: Sun Feb 23 05:54:17 EST 2003 by the ltsp installation script.
# For more information, visit the ltsp homepage
# at http://www.ltsp.org
#
/opt/ltsp/i386 192.168.0.0/255.255.255.0(ro,no_root_squash)
/var/opt/ltsp/swapfiles 192.168.0.0/255.255.255.0(rw,no_root_squash)
#
# The following entries need to be uncommented if you want
# Local App support in ltsp
#
#/home 192.168.0.0/255.255.255.0(rw,no_root_squash)
## LTS-end ##
|
- /etc/fdprm
- Floppy
disk parameter table. Describes what different floppy disk formats look
like. Used by setfdprm.
- /etc/fstab
- The
configuration file for 'mount' and now 'supermount'. It
lists the filesystems mounted automatically at startup by the mount -a
command (in /etc/rc or equivalent startup file). Under Linux, also contains
information about swap areas used automatically by swapon -a.
-
# /etc/fstab: static file system information.
#
# The following is an example. Please see fstab(5) for further details.
# Please refer to mount(1) for a complete description of mount options.
#
# Format:
# <file system> <mount point> <type> <options> <dump> <pass>
#
# dump(8) uses the <dump> field to determine which file systems need
# to be dumped. fsck(8) uses the <pass> column to determine which file
# systems need to be checked--the root file system should have a 1 in
# this field, other file systems a 2, and any file systems that should
# not be checked (such as MS-DOS or NFS file systems) a 0.
#
# The `sw' option indicates that the swap partition is to be activated
# with `swapon -a'.
/dev/hda2 none swap sw 0 0
# The `bsdgroups' option indicates that the file system is to be mounted
# with BSD semantics (files inherit the group ownership of the directory
# in which they live). `ro' can be used to mount a file system read-only.
/dev/hda3 / ext2 defaults 0 1
/dev/hda5 /home ext2 defaults 0 2
/dev/hda6 /var ext2 defaults 0 2
/dev/hda7 /usr ext2 defaults,ro 0 2
/dev/hda8 /usr/local ext2 defaults,bsdgroups 0 2
# The `noauto' option indicates that the file system should not be mounted
# with `mount -a'. `user' indicates that normal users are allowed to mount
# the file system.
/dev/cdrom /cdrom iso9660 defaults,noauto,ro,user 0 0
/dev/fd0 /floppy minix defaults,noauto,user 0 0
/dev/fd1 /floppy minix defaults,noauto,user 0 0
# NFS file systems: server:
/export/usr /usr nfs defaults 0 0
# proc file system:
proc /proc proc defaults 0 0
|
- /etc/ftpaccess
- Determines
who might get ftp-access to your machine.
- /etc/ftpchroot
- List
of ftp users that need to be chrooted.
- /etc/ftpuser
- List
of disallowed ftp users.
- /etc/gateways
- Lists
gateways for 'routed'.
- /etc/gettydefs
- Configures
console-logins.
- /etc/gnome-vfs-mime-magic
- MIME
magic patterns as used by the Gnome VFS library.
- /etc/group
- Similar
to /etc/passwd. It lists the configured user groups and who belongs to them.
- /etc/group-
- Old
/etc/group file.
- /etc/gshadow
- Contains
encrypted forms of group passwords.
- /etc/gshadow-
- Old
/etc/gshadow file.
- /etc/hostname
- Contains
the hostname of your machine (can be fully qualified or not).
- /etc/host.conf
- Determines
the search order for look-ups (usually hosts bind, i.e. "check
/etc/hosts first and then look for a DNS").
- /etc/hosts
- This
file is used to define a system name and domain combination with a specific
IP address. This file needs to always contain an entry for an IP address, if
the machine is connected to the network.
### etherconf DEBCONF AREA. DO NOT EDIT THIS AREA OR INSERT TEXT BEFORE IT.
127.0.0.1 localhost ::1 localhost
ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
192.168.0.99 debian.localdomain.com debian
### END OF DEBCONF AREA. PLACE YOUR EDITS BELOW; THEY WILL BE PRESERVED.
192.168.0.1 ws001
|
- /etc/hosts.allow
- Part
of the tcp-wrappers system to control access to your machine's services.
It lists hosts that are allowed to access the system and specific daemons.
# /etc/hosts.allow: list of hosts that are allowed to access the
# system.
# See the manual pages hosts_access(5), hosts_options(5)
# and /usr/doc/netbase/portmapper.txt.gz
#
# Example: ALL: LOCAL @some_netgroup
# ALL: .foobar.edu EXCEPT terminalserver.foobar.edu
#
# If you're going to protect the portmapper use the name "portmap"
# for the daemon name. Remember that you can only use the keyword
# "ALL" and IP addresses (NOT host or domain names) for the
# portmapper. See portmap(8) and /usr/doc/portmap/portmapper.txt.gz
# for further information.
bootpd: 0.0.0.0 in.tftpd: 192.168.0.
portmap: 192.168.0.
rpc.mountd: 192.168.0.
rpc.nfsd: 192.168.0.
gdm: 192.168.0.
nasd: 192.168.0.
|
- /etc/hosts.deny
- part
of the tcp-wrappers system to control access to your machine's services.
It lists hosts that are not allowed to access the system.
# Example: ALL: some.host.name, .some.domain
# ALL EXCEPT in.fingerd: other.host.name, .other.domain
#
# If you're going to protect the portmapper use the name "portmap"
# for the daemon name. Remember that you can only use the keyword
# "ALL" and IP addresses (NOT host or domain names) for the
# portmapper. See portmap(8) and /usr/doc/portmap/portmapper.txt.gz
# for further information.
#
# The PARANOID wildcard matches any host whose name does not match
# its address. You may wish to enable this to ensure any programs
# that don't validate looked up hostnames still leave understandable
# logs. In past versions of Debian this has been the default.
# ALL: PARANOID
|
- /etc/httpd
- Apache
configuration files. Apache is a versatile, high-performance HTTP server.
The most popular server in the world, Apache features a modular design and
supports dynamic selection of extension modules at runtime. Its strong
points are its range of possible customization, dynamic adjustment of the
number of server processes, and a whole range of available modules including
many authentication mechanisms, server-parsed HTML, server-side includes,
access control, CERN httpd metafiles emulation, proxy caching, etc. Apache
also supports multiple virtual homing.
- /etc/identd.conf
- TCP/IP
IDENT protocol server. It implements the TCP/IP proposed standard IDENT user
identification protocol (RFC 1413). identd operates by looking up specific
TCP/IP connections and returning the username of the process owning the
connection. It can also return other information besides the username.
# /etc/identd.conf - an example configuration file
#-- The syslog facility for error messages
# syslog:facility = daemon
#-- User and group (from passwd database) to run as
server:user = nobody
#-- Override the group id
# server:group = kmem
#-- What port to listen on when started as a daemon or from /etc/inittab
# server:port = 113
#-- The socket backlog limit
# server:backlog = 256
#-- Where to write the file containing our process id
# server:pid-file = "/var/run/identd/identd.pid"
#-- Maximum number of concurrent requests allowed (0 = unlimited)
# server:max-requests = 0
#-- Enable some protocol extensions like "VERSION" or "QUIT"
protocol:extensions = enabled
#-- Allow multiple queries per connection
protocol:multiquery = enabled
#-- Timeout in seconds since connection or last query. Zero = disable
# protocol:timeout = 120
#-- Maximum number of threads doing kernel lookups
# kernel:threads = 8
#-- Maximum number of queued kernel lookup requests
# kernel:buffers = 32
#-- Maximum number of time to retry a kernel lookup in case of failure
# kernel:attempts = 5
#-- Disable username lookups (only return uid numbers)
# result:uid-only = no
#-- Enable the ".noident" file
# result:noident = enabled
#-- Charset token to return in replies
# result:charset = "US-ASCII"
#-- Opsys token to return in replies
# result:opsys = "UNIX"
#-- Log all request replies to syslog (none == don't)
# result:syslog-level = none
#-- Enable encryption (only available if linked with a DES library)
# result:encrypt = no
#-- Path to the DES key file (only available if linked with a DES library)
# encrypt:key-file = "/usr/local/etc/identd.key"
#-- Include a machine local configuration file
# include = /etc/identd.conf
|
- /etc/inetd.conf
- Configuration
of services that are started by the INETD TCP/IP super server.
'inetd' is now deprecated. 'xinetd' has taken its place. See
/etc/xinet.conf for further details.
# /etc/inetd.conf: see inetd(8) for further information.
#
# Internet server configuration database
#
#
# Lines starting with "#:LABEL:" or "#<off>#" should not
# be changed unless you know what you are doing!
#
# If you want to disable an entry so it isn't touched during
# package updates just comment it out with a single '#' character.
#
# Packages should modify this file by using update-inetd(8)
#
# <service_name> <sock_type> <proto>
# <flags> <user> <server_path>
# <args>
#
#:INTERNAL: Internal services
#echo stream tcp nowait root internal
#echo dgram udp wait root internal
#chargen stream tcp nowait root internal
#chargen dgram udp wait root internal
discard stream tcp nowait root internal
discard dgram udp wait root internal
daytime stream tcp nowait root internal
#daytime dgram udp wait root internal
time stream tcp nowait root internal
#time dgram udp wait root internal
#:STANDARD: These are standard services.
ftp stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.ftpd
telnet stream tcp nowait telnetd.telnetd /usr/sbin/tcpd
/usr/sbin/in.telnetd
#:MAIL: Mail, news and uucp services.
smtp stream tcp nowait mail /usr/sbin/exim exim -bs
imap2 stream tcp nowait root /usr/sbin/tcpd /usr/sbin/imapd
imap3 stream tcp nowait root /usr/sbin/tcpd /usr/sbin/imapd
#:INFO: Info services
ident stream tcp wait identd /usr/sbin/identd identd
finger stream tcp nowait nobody /usr/sbin/tcpd
/usr/sbin/in.fingerd
#:BOOT: Tftp service is provided primarily for booting.
#Most sites run this only on machines acting as "boot servers."
tftp dgram udp wait nobody /usr/sbin/tcpd
/usr/sbin/in.tftpd -s /tftpboot
|
- /etc/init.d
Order of scripts run in /etc/rc?.d
==================================
0. Overview.
All scripts executed by the init system are located in /etc/init.d.
The directories /etc/rc?.d (? = S, 0 .. 6) contain relative links to
those scripts. These links are named S<2-digit-number><
original-name> or K<2-digit-number><original-name>.
If a scripts has the ".sh" suffix it is a bourne shell script and
MAY be handled in an optimized manner. The behaviour of executing the
script in an optimized way will not differ in any way from it being
forked and executed in the regular way.
The following runlevels are defined:
N System bootup (NONE).
S Single user mode (not to be switched to directly)
0 halt
1 single user mode
2 .. 5 multi user mode
6 reboot
1. Boot.
When the systems boots, the /etc/init.d/rcS script is executed. It
in turn executes all the S* scripts in /etc/rcS.d in alphabetical
(and thus numerical) order. The first argument passed to the
executed scripts is "start". The runlevel at this point is
"N" (none).
Only things that need to be run once to get the system in a consistent
state are to be run. The rcS.d directory is NOT meant to replace rc.local.
One should not start daemons in this runlevel unless absolutely
necessary. Eg, NFS might need the portmapper, so it is OK to start it
early in the boot process. But this is not the time to start the
squid proxy server.
2. Going multiuser.
After the rcS.d scripts have been executed, init switches to the
default runlevel as specified in /etc/inittab, usually "2".
Init then executes the /etc/init.d/rc script which takes care of
starting the services in /etc/rc2.d.
Because the previous runlevel is "N" (none) the /etc/rc2.d/KXXxxxx
scripts will NOT be executed - there is nothing to stop yet,
the system is busy coming up.
If for example there is a service that wants to run in runlevel 4
and ONLY in that level, it will place a KXXxxxx script in
/etc/rc{2,3,5}.d to stop the service when switching out of runlevel 4.
We do not need to run that script at this point.
The /etc.rc2.d/SXXxxxx scripts will be executed in alphabetical
order, with the first argument set to "start".
3. Switching runlevels.
When one switches from (for example) runlevel 2 to runlevel 3,
/etc/init.d/rc will first execute in alphabetical order all K
scripts for runlevel 3 (/etc/rc3.d/KXXxxxx) with as first argument
"stop" and then all S scripts for runlevel 3 (/etc/rc3.d/SXXxxxx)
with as first argument "start".
As an optimization, a check is made for each "service" to see if
it was already running in the previous runlevel. If it was, and there
is no K (stop) script present for it in the new runlevel, there is
no need to start it a second time so that will not be done.
On the other hand, if there was a K script present, it is assumed the
service was stopped on purpose first and so needs to be restarted.
We MIGHT make the same optimization for stop scripts as well-
if no S script was present in the previous runlevel, we can assume
that service was not running and we don't need to stop it either.
In that case we can remove the "coming from level N" special case
mentioned above in 2). But right now that has not been implemented.
4. Single user mode.
Switching to single user mode is done by switching to runlevel 1.
That will cause all services to be stopped (assuming they all have
a K script in /etc/rc1.d). The runlevel 1 scripts will then switch
to runlevel "S" which has no scripts - all it does is spawn
a shell directly on /dev/console for maintenance.
5. Halt/reboot
Going to runlevel 0 or 6 will cause the system to be halted or rebooted,
respectively. For example, if we go to runlevel 6 (reboot) first
all /etc/rc6.d/KXXxxxx scripts will be executed alphabetically with
"stop" as the first argument.
Then the /etc/rc6.d/SXXxxxx scripts will be executed alphabetically
with "stop" as the first argument as well. The reason is that there
is nothing to start any more at this point - all scripts that are
run are meant to bring the system down.
In the future, the /etc/rc6.d/SXXxxxx scripts MIGHT be moved to
/etc/rc6.d/K1XXxxxx for clarity.
|
- /etc/inittab
- Boot-time
system configuration/initialization script. Tells init how to handle
runlevels. It sets the default runlevel. This is run first except when
booting in emergency (-b) mode. It also enables a user to startup a getty
session on an external device such as the serial ports. To add terminals or
dial-in modem lines to a system, just add more lines to /etc/inittab, one
for each terminal or dial-in line. For more details, see the manual pages
init, inittab, and getty. If a command fails when it starts, and init is
configured to restart it, it will use a lot of system resources: init starts
it, it fails, init starts it, it fails, and so on. To prevent this, init
will keep track of how often it restarts a command, and if the frequency
grows to high, it will delay for five minutes before restarting again.
/etc/inittab also has some special features that allow init to react to
special circumstances. powerwait Allows init to shut the system down, when
the power fails. This assumes the use of a UPS, and software that watches
the UPS and informs init that the power is off. ctrlaltdel Allows init to
reboot the system, when the user presses ctrl-alt-del on the console
keyboard. Note that the system administrator can configure the reaction to
ctrl-alt-del to be something else instead, e.g., to be ignored, if the
system is in a public location. sysinit Command to be run when the system is
booted. This command usually cleans up /tmp, for example. The list above is
not exhaustive. See your inittab manual page for all possibilities, and for
details on how to use the ones above. To set (or reset) initial terminal
colours. The following shell script should work for VGA consoles: for n in 1
2 4 5 6 7 8; do setterm -fore yellow -bold on -back blue -store >
/dev/tty$n done Substitute your favorite colors, and use /dev/ttyS$n for
serial terminals. To make sure they are reset when people log out (if
they've been changed) replace the references to getty (or mingetty or
uugetty or whatever) in /etc/inittab with references to /sbin/mygetty.
#!/bin/sh setterm -fore yellow -bold on -back blue -store > $1 exec
/sbin/mingetty $@ An example /etc/inittab is provided below.
# /etc/inittab: init(8) configuration.
# $Id: etc.xml,v 1.10 2004/02/03 21:42:57 binh Exp $
# The default runlevel. id:2:initdefault:
# Boot-time system configuration/initialization script.
# This is run first except when booting in emergency (-b) mode.
si::sysinit:/etc/init.d/rcS
# What to do in single-user mode.
~~:S:wait:/sbin/sulogin
# /etc/init.d executes the S and K scripts upon change
# of runlevel.
#
# Runlevel 0 is halt.
# Runlevel 1 is single-user.
# Runlevels 2-5 are multi-user.
# Runlevel 6 is reboot.
l0:0:wait:/etc/init.d/rc 0 l1:1:wait:/etc/init.d/rc 1
l2:2:wait:/etc/init.d/rc 2 l3:3:wait:/etc/init.d/rc 3
l4:4:wait:/etc/init.d/rc 4 l5:5:wait:/etc/init.d/rc 5
l6:6:wait:/etc/init.d/rc 6
# Normally not reached, but fallthrough in case of emergency.
z6:6:respawn:/sbin/sulogin
# What to do when CTRL-ALT-DEL is pressed.
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
# Action on special keypress (ALT-UpArrow).
#kb::kbrequest:/bin/echo "Keyboard Request
#--edit /etc/inittab to let this work."
# What to do when the power fails/returns.
pf::powerwait:/etc/init.d/powerfail start
pn::powerfailnow:/etc/init.d/powerfail now
po::powerokwait:/etc/init.d/powerfail stop
# /sbin/getty invocations for the runlevels.
#
# The "id" field MUST be the same as the last
# characters of the device (after "tty").
#
# Format:
# <id>:<runlevels>:<action>:<process>
#
# Note that on most Debian systems tty7 is used by the X Window System,
# so if you want to add more getty's go ahead but skip tty7 if you run X.
#
1:2345:respawn:/sbin/getty 38400 tty1 2:23:respawn:/sbin/getty 38400 tty2
3:23:respawn:/sbin/getty 38400 tty3 4:23:respawn:/sbin/getty 38400 tty4
5:23:respawn:/sbin/getty 38400 tty5 6:23:respawn:/sbin/getty 38400 tty6
# Example how to put a getty on a serial line (for a terminal)
#
#T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100
#T1:23:respawn:/sbin/getty -L ttyS1 9600 vt100
# Example how to put a getty on a modem line.
#
#T3:23:respawn:/sbin/mgetty -x0 -s 57600 ttyS3
Undocumented features
The letters A-C can be used to spawn a daemon listed in /etc/inittab. For
example, assuming you want to start getty on a port to receive a call, but
only after receiving a voice call first (and not all the time). Furthermore,
you want to be able to receive a data or a fax call and that when you get
the voice message you'll know which you want. You insert two new lines
in /etc/inittab, each with its own ID, and each with a runlevel such as A
for data and B for fax. When you know which you need, you simply spawn the
appropriate daemon by calling 'telinit A' or 'telinit B'.
The appropriate getty is put on the line until the first call is received.
When the caller terminates the connection, the getty drops because, by
definition, on demand will not respawn. The other two letters, S and Q, are
special. S brings you system to maintenance mode and is the same as changing
state to runlevel 1. The Q is used to tell init to reread inittab. The
/etc/inittab file can be changed as often as required, but will only be read
under certain circumstances: -One of its processes dies (do you need to
respawn another?) -On a powerful signal from a power daemon (or a command
line) -When told to change state by telinit The Q argument tells init to
reread the /etc/inittab file. Even though it is called the System V runlevel
system runlevels 7-9 are legitimate runlevels that can be used if necessary.
The administrator must remember to alter the inittab file though and also to
create the required rc?.d files.
|
- /etc/inputrc
- Global
inputrc for libreadline. Readline is a function that gets a line from a user
and automatically edits it.
- /etc/isapnp.conf
- Configuration
file for ISA based cards. This standard is virtually redundant in new
systems. The 'isapnptools' suite of ISA Plug-And-Play configuration
utilities is used to configure such devices. These programs are suitable for
all systems, whether or not they include a PnP BIOS. In fact, PnP BIOS adds
some complications because it may already activate some cards so that the
drivers can find them, and these tools can unconfigure them, or change their
settings causing all sorts of nasty effects.
- /etc/isdn
- ISDN
configuration files.
- /etc/issue
- Output
by getty before the login prompt. Usually contains a short description or
welcoming message to the system. The contents are up to the system
administrator. Debian GNU/\s 3.0 \n \l
- /etc/issue.net
- Presents
the welcome screen to users who login remotely to your machine (whereas
/etc/issue determines what a local user sees on login). Debian GNU/%s 3.0 %h
- /etc/kde
- KDE
initialization scripts and KDM configuration.
- /etc/kde/kdm
- Location
for the K Desktop Manager files. kdm manages a collection of X servers,
which may be on the local host or remote machines. It provides services
similar to those provided by init, getty, and login on character-based
terminals: prompting for login name and password, authenticating the user,
and running a session. kdm supports XDMCP (X Display Manager Control
Protocol) and can also be used to run a chooser process which presents the
user with a menu of possible hosts that offer XDMCP display management.
- /etc/kderc
- System
wide KDE initialization script. Commands here executed every time the KDE
environment is loaded. It's a link to /etc/kde2/system.kdeglobals
-
[Directories]
dir_config=/etc/kde2
dir_html=/usr/share/doc/kde/HTML
dir_cgi=/usr/lib/cgi-bin
dir_apps=/usr/share/applnk
dir_mime=/usr/share/mimelnk
dir_services=/usr/share/services
dir_servicetypes=/usr/share/servicetypes
[General]
TerminalApplication=x-terminal-emulator
|
- /etc/ld.so.conf, /etc/ld.so.cache
-
- /etc/ld.so.conf is a file
containing a list of colon, space, tab, newline, or comma separated
directories in which to search for libraries. /etc/ld.so.cache containing an
ordered list of libraries found in the directories specified in
/etc/ld.so.conf. This file is not in human readable format, and is not
intended to be edited.
- 'ldconfig' creates the necessary
links and cache (for use by the run-time linker, ld.so) to the most recent
shared libraries found in the directories specified on the command line, in
the file /etc/ld.so.conf, and in the trusted directories (/usr/lib and
/lib). 'ldconfig' checks the header and file names of the libraries
it encounters when determining which versions should have their links
updated. ldconfig ignores symbolic links when scanning for libraries.
- 'ldconfig' will attempt to deduce the type of ELF libs (ie.
libc5 or libc6/glibc) based on what C libs if any the library was linked
against, therefore when making dynamic libraries, it is wise to explicitly
link against libc (use -lc).
- Some existing libs do not contain
enough information to allow the deduction of their type, therefore the
/etc/ld.so.conf file format allows the specification of an expected type.
This is only used for those ELF libs which we can not work out. The format
is like this "dirname=TYPE", where type can be libc4, libc5 or
libc6. (This syntax also works on the command line). Spaces are not allowed.
Also see the -p option.
- Directory names containing an = are no
longer legal unless they also have an expected type specifier.
- 'ldconfig' should normally be run by the super-user as it may
require write permission on some root owned directories and files. It is
normally run automatically at bootup or manually whenever new shared
libraries are installed.
- /usr/X11R6/lib
- X libraries.
- /usr/local/lib
- Local libraries.
- /etc/lilo.conf
- Configuration
file for the Linux boot loader 'lilo'. 'lilo' is the
original OS loader and can load Linux and others. The 'lilo' package
normally contains lilo (the installer) and boot-record-images to install
Linux, OS/2, DOS and generic Boot Sectors of other Oses. You can use Lilo to
manage your Master Boot Record (with a simple text screen, text menu or
colorful splash graphics) or call 'lilo' from other boot-loaders to
jump-start the Linux kernel.
-
Prompt #Prompt user to select
OS choice at boot timeout=300 # Amount of time to wait before default OS
# started (in ms)
default=Debian4 #Default OS to be loaded
vga=normal #VGA mode
boot=/dev/had #location of MBR
map=/boot/map #location of kernel
install=/boot/boot-bmp.b #File to be installed as boot sector
bitmap=/boot/debian.bmp #LILO boot image
bmp-table=30p,100p,1,10 #Colours
selectable bmp-colors=13,,0,1,,0 #Colours chosen
lba32 #Required on most new systems to overcome
#1024 cylinder problem
image=/vmlinuz #name of kernel
image label=Debian #a label
read-only #file system to be mounted read only
root=/dev/hda6 #location of root filesystem
image=/boot/bzImage
label=Debian4
read-only
root=/dev/hda6
image=/mnt/redhat/boot/vmlinuz
label=Redhat
initrd=/mnt/redhat/boot/initrd-2.4.18-14.img
read-only
root=/dev/hda5
vga=788
append=" hdc=ide-scsi hdd=ide-scsi"
image=/mnt/mandrake/boot/vmlinuz
label="Mandrake"
root=/dev/hda7
initrd=/mnt/mandrake/boot/initrd.img
append="devfs=mount hdc=ide-scsi
acpi=off quiet"
vga=788
read-only
other=/dev/hda2
table=/dev/hda
loader=/boot/chain.b
label=FBSD
other=/dev/hda1
label=Windows
table=/dev/hda
other=/dev/fd0
label=floppy unsafe
|
- /etc/local.gen
- This
file lists locales that you wish to have built. You can find a list of valid
supported locales at /usr/share/i18n/SUPPORTED. Other combinations are
possible, but may not be well tested. If you change this file, you need to
re-run locale-gen.
- /etc/locale.alias
- Locale
name alias data base.
- /etc/login.defs
- Configuration
control definitions for the login package. An inordinate number of
attributes can be altered via this single file such as the location of mail,
delay in seconds after a failed login, enabling display of fail log
information, display of unknown username login failures, shell environment
variables, etc....
- /etc/logrotate.conf
- The
logrotate utility is designed to simplify the administration of log files on
a system which generates a lot of log files. Logrotate allows for the
automatic rotation compression, removal and mailing of log files. Logrotate
can be set to handle a log file daily, weekly, monthly or when the log file
gets to a certain size. Normally, logrotate runs as a daily cron job.
# see "man logrotate" for details
# rotate log files weekly
weekly
# keep 4 weeks worth of backlogs
rotate 4
# create new (empty) log files after rotating old ones
create
# uncomment this if you want your log files compressed
#compress
# packages drop log rotation information into this directory
include /etc/logrotate.d
# no packages own wtmp, or btmp -- we'll rotate them here
/var/log/wtmp {
monthly
create 0664 root utmp
rotate 1
}
/var/log/btmp {
missingok
monthly
create 0664 root utmp
rotate 1
}
# system-specific logs may be configured here
|
- /etc/ltrace.conf
- Configuration
file for ltrace (Library Call Tracer). It tracks runtime library calls in
dynamically linked programs. 'ltrace' is a debugging program which
runs a specified command until it exits. While the command is executing,
ltrace intercepts and records the dynamic library calls which are called by
the executed process and the signals received by that process. It can also
intercept and print the system calls executed by the program. The program to
be traced need not be recompiled for this, so you can use it on binaries for
which you don't have the source handy. You should install ltrace if you
need a sysadmin tool for tracking the execution of processes.
- /etc/magic
- Magic
local data and configuration file for the file(1) command. Contains the
descriptions of various file formats based on which file guesses the type of
the file. Insert here your local magic data. Format is described in
magic(5).
- /etc/mail.rc
- Initialization
file for 'mail'. 'mail' is an intelligent mail processing
system which has a command syntax reminiscent of ed with lines replaced by
messages. It's basically a command line version of Microsoft Outlook.
- /etc/mailcap
- 'metamail'
capabilities file. The mailcap file is read by the metamail program to
determine how to display non-text at the local site. The syntax of a mailcap
file is quite simple, at least compared to termcap files. Any line that
starts with "#" is a comment. Blank lines are ignored. Otherwise,
each line defines a single mailcap entry for a single content type. Long
lines may be continued by ending them with a backslash character, \. Each
individual mailcap entry consists of a content-type specification, a command
to execute, and (possibly) a set of optional "flag" values.
- /etc/mailcap.order
- The
mailcap ordering specifications. The order of entries in the /etc/mailcap
file can be altered by editing the /etc/mailcap.order file. Each line of
that file specifies a package and an optional mime type. Mailcap entries
that match will be placed in the order of this file. Entries that don't
match will be placed later.
- /etc/mailname
- Mail
server hostname. Normally the same as the hostname.
- /etc/menu,
/etc/menu-methods
- The menu package was inspired by the
install-fvwm2-menu program from the old fvwm2 package. However, menu tries
to provide a more general interface for menu building. With the update-menus
command from this package, no package needs to be modified for every X
window manager again, and it provides a unified interface for both text-and
X-oriented programs.
When a package that wants to add something
to the menu tree gets installed, it will run update-menus in its postinstall
script. Update-menus then reads in all menu files in /etc/menu/
/usr/lib/menu and /usr/lib/menu/default, and stores the menu entries of all
installed packages in memory. Once that has been done, it will run the
menu-methods in /etc/menu-methods/*, and pipe the information about the menu
entries to the menu-methods on stdout, so that the menu-methods can read
this. Each Window Manager or other program that wants to have the debian
menu tree, will supply a menu-method script in /etc/menu-methods/. This
menu-method then knows how to generate the startup-file for that window
manager. To facilitate this task for the window-manager maintainers, menu
provides a install-menu program. This program can generate the startup files
for just about every window manager.
- /etc/mgetty+sendfax
- Configuration
files for use of mgetty as the interface on the serial port. The mgetty
routine special routine has special features for handling things such as
dial up connections and fax connections.
- /etc/mime.types
- MIME-TYPES
and the extensions that represent them. This file is part of the
"mime-support" package. Note: Compression schemes like
"gzip", "bzip", and "compress" are not actually
"mime-types". They are "encodings" and hence must _not_ have
entries in this file to map their extensions. The "mime-type" of an
encoded file refers to the type of data that has been encoded, not the type
of the encoding.
- /etc/minicom
- 'minicom'
configuration files. 'minicom' is a communication program which
somewhat resembles the shareware program TELIX but is free with source code
and runs under most unices. Features include dialling directory with
auto-redial, support for UUCP-style lock files on serial devices, a separate
script language interpreter, capture to file, multiple users with individual
configurations, and more.
- /etc/modules
- List
of modules to be loaded at startup.
# /etc/modules: kernel modules to load at boot time.
#
# This file should contain the names of kernel modules that are
# to be loaded at boot time, one per line. Comments begin with
# a "#", and everything on the line after them are ignored.
unix
af_packet
via-rhine
cmpci
ne2k-pci
nvidia
|
- /etc/modules.conf
### This file is automatically generated by update-modules"
#
# Please do not edit this file directly. If you want to change or add
# anything please take a look at the files in /etc/modutils and read
# the manpage for update-modules.
#
### update-modules: start processing /etc/modutils/0keep
# DO NOT MODIFY THIS FILE!
# This file is not marked as conffile to make sure if you upgrade modutils
# it will be restored in case some modifications have been made.
#
# The keep command is necessary to prevent insmod and friends from ignoring
# the builtin defaults of a path-statement is encountered. Until all other
# packages use the new `add path'-statement this keep-statement is essential
# to keep your system working
keep
### update-modules: end processing /etc/modutils/0keep
### update-modules: start processing /etc/modutils/actions
# Special actions that are needed for some modules
# The BTTV module does not load the tuner module automatically,
# so do that in here
post-install bttv insmod tuner
post-remove bttv rmmod tuner
### update-modules: end processing /etc/modutils/actions
### update-modules: start processing /etc/modutils/aliases
# Aliases to tell insmod/modprobe which modules to use
# Uncomment the network protocols you don't want loaded:
# alias net-pf-1 off # Unix
# alias net-pf-2 off # IPv4
# alias net-pf-3 off # Amateur Radio AX.25
# alias net-pf-4 off # IPX
# alias net-pf-5 off # DDP / appletalk
# alias net-pf-6 off # Amateur Radio NET/ROM
# alias net-pf-9 off # X.25
# alias net-pf-10 off # IPv6
# alias net-pf-11 off # ROSE / Amateur Radio X.25 PLP
# alias net-pf-19 off # Acorn Econet
alias char-major-10-175 agpgart
alias char-major-10-200 tun
alias char-major-81 bttv
alias char-major-108 ppp_generic
alias /dev/ppp ppp_generic
alias tty-ldisc-3 ppp_async
alias tty-ldisc-14 ppp_synctty
alias ppp-compress-21 bsd_comp
alias ppp-compress-24 ppp_deflate
alias ppp-compress-26 ppp_deflate
# Crypto modules (see http://www.kerneli.org/)
alias loop-xfer-gen-0 loop_gen
alias loop-xfer-3 loop_fish2
alias loop-xfer-gen-10 loop_gen
alias cipher-2 des
alias cipher-3 fish2
alias cipher-4 blowfish
alias cipher-6 idea
alias cipher-7 serp6f
alias cipher-8 mars6
alias cipher-11 rc62
alias cipher-15 dfc2
alias cipher-16 rijndael
alias cipher-17 rc5
### update-modules: end processing /etc/modutils/aliases
### update-modules: start processing /etc/modutils/ltmodem-2.4.18
# lt_drivers: autoloading and insertion parameter usage
alias char-major-62 lt_serial
alias /dev/tts/LT0 lt_serial
alias /dev/modem lt_serial
# options lt_modem vendor_id=0x115d device_id=0x0420 Forced=3,0x130,0x2f8
# section for lt_drivers ends
### update-modules: end processing /etc/modutils/ltmodem-2.4.18
### update-modules: start processing /etc/modutils/paths
# This file contains a list of paths that modprobe should scan,
# beside the once that are compiled into the modutils tools
# themselves.
### update-modules: end processing /etc/modutils/paths
### update-modules: start processing /etc/modutils/ppp
alias /dev/ppp ppp_generic
alias char-major-108 ppp_generic
alias tty-ldisc-3 ppp_async
alias tty-ldisc-14 ppp_synctty
alias ppp-compress-21 bsd_comp
alias ppp-compress-24 ppp_deflate
alias ppp-compress-26 ppp_deflate
### update-modules: end processing /etc/modutils/ppp
### update-modules: start processing /etc/modutils/setserial
#
# This is what I wanted to do, but logger is in /usr/bin, which isn't
# loaded when the module is first loaded into the kernel at boot time!
#
#post-install serial /etc/init.d/setserial start |
#logger -p daemon.info -t "setserial-module reload"
#pre-remove serial /etc/init.d/setserial stop |
#logger -p daemon.info -t "setserial-module uload"
#
alias /dev/tts serial
alias /dev/tts/0 serial
alias /dev/tts/1 serial
alias /dev/tts/2 serial
alias /dev/tts/3 serial
post-install serial /etc/init.d/setserial modload > /dev/null 2> /dev/null
pre-remove serial /etc/init.d/setserial modsave > /dev/null 2> /dev/null
### update-modules: end processing /etc/modutils/setserial
### update-modules: start processing /etc/modutils/arch/i386
alias parport_lowlevel parport_pc
alias char-major-10-144 nvram
alias binfmt-0064 binfmt_aout
alias char-major-10-135 rtc
### update-modules: end processing /etc/modutils/arch/i386
|
- /etc/modutils
- These
utilities are intended to make a Linux modular kernel manageable for all
users, administrators and distribution maintainers.
- /etc/mtools
- Debian
default mtools configuration file. The mtools series of commands work with
MS-DOS files and directories on floppy disks. This allows you to use Linux
with MS-DOS formatted diskettes on DOS and Windows systems.
- /etc/manpath.conf
- This
file is used by the man_db package to configure the man and cat paths. It is
also used to provide a manpath for those without one by examining their PATH
environment variable. For details see the manpath(5) man page.
- /etc/mediaprm
- Was
formally named /etc/fdprm. See /etc/fdprm for further details.
- /etc/motd
- The
message of the day, automatically output after a successful login. Contents
are up to the system administrator. Often used for getting information to
every user, such as warnings about planned downtimes. Linux
debian.localdomain.com 2.4.18 #1 Sat Mar 15 00:17:39 EST 2003 i686 unknown
Most of the programs included with the Debian GNU/Linux system are freely
redistributable; the exact distribution terms for each program are described
in the individual files in /usr/share/doc/*/copyright Debian GNU/Linux comes
with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law.
- /etc/mtab
- List
of currently mounted filesystems. Initially set up by the bootup scripts,
and updated automatically by the mount command. Used when a list of mounted
filesystems is needed, e.g., by the df command. This file is sometimes a
symbolic link to /proc/mounts.
- /etc/networks
- List
of networks that the system is currently located on. For example,
192.168.0.0.
- /etc/nsswitch.conf
- System
Database/Name Service Switch configuration file.
- /etc/oss.conf
- OSS
(Open Sound System) configuration file.
- /etc/pam.d/
- This
directory is the home of the configuration files for PAMs, Pluggable
Authentication Modules.
- /etc/postfix/
- Holds
your postfix configuration files. Postfix is now the MTA of choice among
Linux distributions. It is sendmail-compatible, offers improved speed over
sendmail, ease of administration and security. It was originally developed
by IBM and was called the IBM Secure Mailer and is used in many large
commercial networks. It is now the de-facto standard.
- /etc/ppp/
- The
place where your dial-up configuration files are placed. More than likely to
be created by the text menu based pppconfig or other GUI based ppp
configuration utilities such as kppp or gnome-ppp.
- /etc/pam.conf
- Most
programs use a file under the /etc/pam.d/ directory to setup their PAM
service modules. This file is and can be used, but is not recommended.
- /etc/paper.config
- Paper
size configuration file.
- /etc/papersize
- Default
papersize.
- /etc/passwd
- This
is the 'old' password file, It is kept for compatibility and
contains the user database, with fields giving the username, real name, home
directory, encrypted password, and other information about each user. The
format is documented in the passwd man(ual) page.
root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:100:sync:/bin:/bin/sync games:x:5:100:games:/usr/games:/bin/sh
man:x:6:100:man:/var/cache/man:/bin/sh lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh proxy:x:13:13:proxy:/bin:/bin/sh
postgres:x:31:32:postgres:/var/lib/postgres:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
operator:x:37:37:Operator:/var:/bin/sh
list:x:38:38:SmartList:/var/list:/bin/sh irc:x:39:39:ircd:/var:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/home:/bin/sh
binh:x:1000:1000:,,,:/home/binh:/bin/bash
identd:x:100:65534::/var/run/identd:/bin/false
sshd:x:101:65534::/var/run/sshd:/bin/false gdm:x:102:101:Gnome Display
Manager:/var/lib/gdm:/bin/false
telnetd:x:103:103::/usr/lib/telnetd:/bin/false
dummy:x:1001:1001:,,,:/home/dummy:/bin/bash
|
- /etc/passwd-
- Old
/etc/passwd file.
- /etc/printcap
- Printer
configuration (capabilities) file. The definition of all system printers,
whether local or remote, is stored in this file. Its layout is similar to
that of /etc/termcap but it uses a different syntax.
- /etc/profile
- Files
and commands to be executed at login or startup time by the Bourne or C
shells. These allow the system administrator to set global defaults for all
users.
- /etc/profile.d
- Shells
scripts to be executed upon login to the Bourne or C shells. These scripts
are normally called from the /etc/profile file.
- /etc/protocols
- Protocols
definitions file. It describes the various DARPA Internet protocols that are
available from the TCP/IP subsystem. It should be consulted instead of using
the numbers in the ARPA include files or resorting to guesstimation. This
file should be left untouched since changes could result in incorrect IP
packages.
- /etc/pcmcia
- Configuration
files for PCMCIA devices. Generally only useful to laptop users.
- /etc/reportbug.conf
- Configuration
file for reportbug. Reportbug is primarily designed to report bugs in the
Debian distribution. By default it creates an e-mail to the Debian bug
tracking system at mit@bugs.debian.org with information about the bug. Using
the -bts option you can report bugs to other servers also using ddebbugs
such as KDE.org. It is similar to bug but has far greater capabilities while
still maintaining simplicity.
- /etc/rc.boot or /etc/rc?.d
- These
directories contain all the files necessary to control system services
and configure runlevels. A skeleton file is provided in
/etc/init.d/skeleton
- /etc/rcS.d
- The
scripts in this directory are executed once when booting the system, even
when booting directly into single user mode. The files are all symbolic
links, the real files are located in /etc/init.d/. For a more general
discussion of this technique, see /etc/init.d/README.
- /etc/resolv.conf
- Configuration
of how DNS is to occur is defined in this file. It tells the name resolver
libraries where they need to go to find information not found in the
/etc/hosts file. This always has at least one nameserver line, but
preferably three. The resolver uses each in turn. More than the first three
can be included but anything beyond the first three will be ignored. Two
lines that appear in the /etc/resolv.conf file are domain and search. Both
of these are mutually exclusive options, and where both show up, the last
one wins. Other entries beyond the three discussed here are listed in the
man pages but aren't often used.
- /etc/rmt
- This
is not a mistake. This shell script (/etc/rmt) has been provided for
compatibility with other Unix-like systems, some of which have utilities
that expect to find (and execute) rmt in the /etc directory on remote
systems.
- /etc/rpc
- The
rpc file contains user readable names that can be used in place of rpc
program numbers. Each line has the following information: -name of server
for the rpc program -rpc program number -aliases Items are separated by any
number of blanks and/or tab characters. A ``#'' indicates the
beginning of a comment; characters up to the end of the line are not
interpreted by routines which search the file.
# /etc/rpc:
# $Id: etc.xml,v 1.10 2004/02/03 21:42:57 binh Exp $
#
# rpc 88/08/01 4.0 RPCSRC; from 1.12 88/02/07 SMI
portmapper 100000 portmap sunrpc
rstatd 100001 rstat rstat_svc rup perfmeter
rusersd 100002 rusers
nfs 100003 nfsprog
ypserv 100004 ypprog
mountd 100005 mount showmount
ypbind 100007
walld 100008 rwall shutdown
yppasswdd 100009 yppasswd
etherstatd 100010 etherstat
rquotad 100011 rquotaprog quota rquota
sprayd 100012 spray
3270_mapper 100013
rje_mapper 100014
selection_svc 100015 selnsvc
database_svc 100016
rexd 100017 rex
alis 100018
sched 100019
llockmgr 100020
nlockmgr 100021
x25.inr 100022
statmon 100023
status 100024
bootparam 100026
ypupdated 100028 ypupdate
keyserv 100029 keyserver
tfsd 100037
nsed 100038
nsemntd 100039
pcnfsd 150001
amd 300019 amq
sgi_fam 391002
ugidd 545580417
bwnfsd 788585389
|
- /etc/samba
- Samba
configuration files. A 'LanManager' like file and printer server for
Unix. The Samba software suite is a collection of programs that implements
the SMB protocol for unix systems, allowing you to serve files and printers
to Windows, NT, OS/2 and DOS clients. This protocol is sometimes also
referred to as the LanManager or NetBIOS protocol.
- /etc/sane.d
- Sane
configuration files. SANE stands for "Scanner Access Now Easy" and
is an application programming interface (API) that provides standardized
access to any raster image scanner hardware (flatbed scanner, hand-held
scanner, video- and still-cameras, frame-grabbers, etc.). The SANE API is
public domain and its discussion and development is open to everybody. The
current source code is written for UNIX (including GNU/Linux) and is
available under the GNU General Public License (the SANE API is available to
proprietary applications and backends as well, however).
SANE is
a universal scanner interface. The value of such a universal interface is
that it allows writing just one driver per image acquisition device rather
than one driver for each device and application. So, if you have three
applications and four devices, traditionally you'd have had to write 12
different programs. With SANE, this number is reduced to seven: the three
applications plus the four drivers. Of course, the savings get even bigger
as more and more drivers and/or applications are added.
Not only
does SANE reduce development time and code duplication, it also raises the
level at which applications can work. As such, it will enable applications
that were previously unheard of in the UNIX world. While SANE is primarily
targeted at a UNIX environment, the standard has been carefully designed to
make it possible to implement the API on virtually any hardware or operating
system.
While SANE is an acronym for ``Scanner Access Now
Easy'' the hope is of course that SANE is indeed sane in the sense
that it will allow easy implementation of the API while accommodating all
features required by today's scanner hardware and applications.
Specifically, SANE should be broad enough to accommodate devices such as
scanners, digital still and video cameras, as well as virtual devices like
image file filters.
If you're familiar with TWAIN, you may
wonder why there is a need for SANE. Simply put, TWAIN does not separate the
user-interface from the driver of a device. This, unfortunately, makes it
difficult, if not impossible, to provide network transparent access to image
acquisition devices (which is useful if you have a LAN full of machines, but
scanners connected to only one or two machines; it's obviously also
useful for remote-controlled cameras and such). It also means that any
particular TWAIN driver is pretty much married to a particular GUI API (be
it Win32 or the Mac API). In contrast, SANE cleanly separates device
controls from their representation in a user-interface. As a result, SANE
has no difficulty supporting command-line driven interfaces or
network-transparent scanning. For these reasons, it is unlikely that there
will ever be a SANE backend that can talk to a TWAIN driver. The converse is
no problem though: it would be pretty straight forward to access SANE
devices through a TWAIN source. In summary, if TWAIN had been just a little
better designed, there would have been no reason for SANE to exist, but
things being the way they are, TWAIN simply isn't SANE.
- /etc/securetty
- Identifies
secure terminals, i.e., the terminals from which root is allowed to log in.
Typically only the virtual consoles are listed, so that it becomes
impossible (or at least harder) to gain superuser privileges by breaking
into a system over a modem or a network.
# /etc/securetty: list of terminals on which root is allowed to login.
# See securetty(5) and login(1).
console
# Standard consoles
tty1
tty2
tty3
tty4
tty5
tty6
tty7
tty8
tty9
tty10
tty11
tty12
# Same as above, but these only occur with devfs devices
vc/1
vc/2
vc/3
vc/4
vc/5
vc/6
vc/7
vc/8
vc/9
vc/10
vc/11
vc/12
|
- /etc/sensors.conf
- Configuration
file for libsensors. A set of libraries designed to ascertain current
hardware states via motherboard sensor chips. Useful statistics such as core
voltages, CPU temperature can be determined through third party utilities
that make user of these libraries such as 'gkrellm'. If you do not
wish to install these packages you may also utilise the /proc filesystem
real-time nature.
- /etc/sudoers
- Sudoers
file. This file must be edited with the 'visudo' command as root.
The sudo command allows an authenticated user to execute an authorized
command as root. Both the effective UID and GID are set to 0 (you are
basically root). It determines which users are authorized and which commands
they are authorized to use. Configuration of this command is via this file.
- /etc/shadow
- Shadow
password file on systems with shadow password software installed (PAMs).
Shadow passwords move the encrypted password from /etc/passwd into
/etc/shadow; the latter is not readable by anyone except root. This makes it
more difficult to crack passwords.
- /etc/shadow-
- Old
/etc/shadow file.
- /etc/sysctl.conf
- Configuration
file for setting system variables, most notably kernel parameters.
'sysctl' is a means of configuring certain aspects of the kernel at
run-time, and the /proc/sys/ directory is there so that you don't even
need special tools to do it!
- /etc/security
- Essential
to security. This subdirectory allows administrators to impose quota limits,
access limits and also to configure PAM environments.
- /etc/serial.conf
- Serial
port configuration. Changeable parameters include speed, baud rate, port,
irq and type.
- /etc/services
- A
definition of the networks, services and the associated port for each
protocol that are available on this system. For example, web services (http)
are assigned to port 80 by default.
# /etc/services:
# $Id: etc.xml,v 1.10 2004/02/03 21:42:57 binh Exp $
#
# Network services, Internet style
#
# Note that it is presently the policy of IANA to assign a single
# well-known port number for both TCP and UDP; hence, most entries
# here have two entries even if the protocol doesn't support UDP
# operations. Updated from RFC 1700, ``Assigned Numbers'' (October
# 1994). Not all ports are included, only the more common ones.
echo 7/tcp
echo 7/udp
discard 9/tcp sink null
discard 9/udp sink null
systat 11/tcp users
daytime 13/tcp daytime
13/udp netstat
15/tcp qotd
17/tcp quote msp
18/tcp # message send protocol
msp 18/udp # message send protocol
chargen 19/tcp ttytst source
chargen 19/udp ttytst source
ftp-data 20/tcp
ftp 21/tcp
fsp 21/udp fspd
ssh 22/tcp # SSH Remote Login Protocol
ssh 22/udp # SSH Remote Login Protocol
telnet 23/tcp
# 24 - private smtp
25/tcp mail
# 26 - unassigned
time 37/tcp timserver
time 37/udp timserver
rlp 39/udp resource # resource location
nameserver 42/tcp name # IEN 116
whois 43/tcp nicname
re-mail-ck 50/tcp # Remote Mail Checking Protocol
re-mail-ck 50/udp # Remote Mail Checking Protocol
domain 53/tcp nameserver # name-domain server domain 53/udp
nameserver netbios-ns 137/tcp # NETBIOS Name Service netbios-ns 137/udp
netbios-dgm 138/tcp # NETBIOS Datagram Service
netbios-dgm 138/udp
netbios-ssn 139/tcp # NETBIOS session service
netbios-ssn 139/udp
x11 6000/tcp x11-0 # X windows system
x11 6000/udp x11-0 # X windows system
- /etc/shells
- Lists
trusted shells. The chsh command allows users to change their login shell
only to shells listed in this file. ftpd, the server process that provides
FTP services for a machine, will check that the user's shell is listed
in /etc/shells and will not let people log in unless the shell is listed
there. There are also some display managers that will passively or actively
(dependent upon on distribution and display manager being used) refuse a
user access to the system unless their shell is one of those listed here.
# /etc/shells: valid login shells
/bin/ash
/bin/bash
/bin/csh
/bin/sh
/usr/bin/es
/usr/bin/ksh
/bin/ksh
/usr/bin/rc
/usr/bin/tcsh
/bin/tcsh
/usr/bin/zsh
/bin/sash
/bin/zsh
/usr/bin/esh
|
- /etc/skel/
- The
default files for each new user are stored in this directory. Each time a
new user is added, these skeleton files are copied into their home
directory. An average system would have: .alias, .bash_profile, .bashrc and
.cshrc files. Other files are left up to the system administrator.
- /etc/sysconfig/
- This
directory contains configuration files and subdirectories for the setup of
system configuration specifics and for the boot process, like
'clock', which sets the timezone, or 'keyboard' which
controls the keyboard map. The contents may vary drastically depending on
which distribution and what utilities you have installed. For example, on a
Redhat or Mandrake based system it is possible to alter an endless array of
attributes from the default desktop to whether DMA should be enabled for
your IDE devices. On our Debian reference system though this folder is
almost expedient containing only two files hwconf and soundcard which are
both configured by the Redhat utilities hwconf and sndconfig respectively.
- /etc/slip
- Configuration
files for the setup and operation of SLIP (serial line IP) interface.
Generally unused nowadays. This protocol has been superceded by the faster
and more efficient PPP protocol.
- /etc/screenrc
- This
is the system wide screenrc. You can use this file to change the default
behavior of screen system wide or copy it to ~/.screenrc and use it as a
starting point for your own settings. Commands in this file are used to set
options, bind screen functions to keys, redefine terminal capabilities, and
to automatically establish one or more windows at the beginning of your
screen session. This is not a comprehensive list of options, look at the
screen manual for details on everything that you can put in this file.
- /etc/scrollkeeper.conf
- A
free electronic cataloging system for documentation. It stores metadata
specified by the http://www.ibiblio.org/osrt/omf/ (Open Source Metadata
Framework) as well as certain metadata extracted directly from documents
(such as the table of contents). It provides various functionality
pertaining to this metadata to help browsers, such as sorting the registered
documents or searching the metadata for documents which satisfy a set of
criteria.
- /etc/ssh
- 'ssh'
configuration files. 'ssh' is a secure rlogin/rsh/rcp replacement
(OpenSSH). This is the portable version of OpenSSH, a free implementation of
the Secure Shell protocol as specified by the IETF secsh working group.
'ssh' (Secure Shell) is a program for logging into a remote machine
and for executing commands on a remote machine. It provides secure encrypted
communications between two untrusted hosts over an insecure network. X11
connections and arbitrary TCP/IP ports can also be forwarded over the secure
channel. It is intended as a replacement for rlogin, rsh and rcp, and can be
used to provide applications with a secure communication channel. It should
be noted that in some countries, particularly Iraq, and Pakistan, it may be
illegal to use any encryption at all without a special permit.
- /etc/syslog.conf
- Lists
where log files should go, what messages are written to them and the level
of verbosity. It is also now possible to filter based on message content,
message integrity, message encryption (near future), portability and better
network forwarding.
- /etc/termcap
- The
terminal capability database. Describes the "escape sequences" by
which various terminals can be controlled. Programs are written so that
instead of directly outputting an escape sequence that only works on a
particular brand of terminal, they look up the correct sequence to do
whatever it is they want to do in /etc/termcap. As a result most programs
work with most kinds of terminals.
- /etc/timezone
- local
timezone.
- /etc/updatedb.conf
- Sets
environment variables that are used by updatedb which therefore configures
the database for 'locate', a utility that locates a pattern in a
database of filenames and returns the filenames that match.
# This file sets environment variables which are used by updatedb
# filesystems which are pruned from updatedb database
PRUNEFS="NFS nfs afs proc smbfs autofs auto iso9660 ncpfs coda devpts ftpfs"
export PRUNEFS
# paths which are pruned from updatedb database
PRUNEPATHS="/tmp /usr/tmp /var/tmp /afs /amd /alex /var/spool"
export PRUNEPATHS
# netpaths which are added
NETPATHS=""
export NETPATHS
|
- /etc/vga
- The
configuration file for the svgalib is stored in this directory. svgalib
provides graphics capabilities to programs running on the system console,
without going through the X Window System. It uses direct access to the
video hardware to provide low-level access to the standard VGA and SVGA
graphics modes. It only works with some video hardware; so use with caution.
- /etc/vim
- Contains
configuration files for both vim and its X based counterpart gvim. A wide
range of options can be accessed though these two files such as automatic
indentation, syntax highlighting, etc....
- /etc/xinetd.d/
- The
original 'inetd' daemon has now been superceded by the much improved
'xinetd'. 'inetd' should be run at boot time by
/etc/init.d/inetd (or /etc/rc.local on some systems). It then listens for
connections on certain Internet sockets. When a connection is found on one
of its sockets, it decides what service the socket corresponds to, and
invokes a program to service the request. After the program is finished, it
continues to listen on the socket (except in some cases). Essentially, inetd
allows running one daemon to invoke several others, reducing load on the
system. Services controlled via xinetd put their configuration files here.
- /etc/zlogin
- System-wide
.zlogin file for zsh(1). This file is sourced only for login shells. It
should contain commands that should be executed only in login shells. It
should be used to set the terminal type and run a series of external
commands (fortune, msgs, from, etc.)
- /etc/zlogout
- Commands
to be executed upon user exit from the zsh. Its control is system-wide
but the .zlogout file for zsh(1) does override it in terms of importance.
- /etc/zprofile
- System-wide
.zprofile file for zsh(1). This file is sourced only for login shells (i.e.
Shells invoked with "-" as the first character of argv[0], and
shells invoked with the -l flag.)
- /etc/zshenv
- System-wide
.zshenv file for zsh(1). This file is sourced on all invocations of the
shell. If the -f flag is present or if the NO_RCS option is set within this
file, all other initialization files are skipped. This file should contain
commands to set the command search path, plus other important environment
variables. This file should not contain commands that produce output or
assume the shell is attached to a tty.
- /etc/zshrc
- System-wide
.zshrc file for zsh(1). This file is sourced only for interactive shells. It
should contain commands to set up aliases, functions, options, key bindings,
etc.
Compliance with the FSSTND requires that the following directories, or
symbolic links to directories are required in /etc:
opt Configuration for /opt
X11 Configuration for the X Window system (optional)
sgml Configuration for SGML (optional)
xml Configuration for XML (optional)
The following directories, or symbolic links to directories must be in /etc,
if the corresponding subsystem is installed:
opt Configuration for /opt
The following files, or symbolic links to files, must be in /etc if the
corresponding subsystem is installed (it is recommended that files be
stored in subdirectories of /etc/ rather than directly in /etc:
csh.login Systemwide initialization file for C shell logins (optional)
exports NFS filesystem access control list (optional)
fstab Static information about filesystems (optional)
ftpusers FTP daemon user access control list (optional)
gateways File which lists gateways for routed (optional)
gettydefs Speed and terminal settings used by getty (optional)
group User group file (optional)
host.conf Resolver configuration file (optional)
hosts Static information about host names (optional)
hosts.allow Host access file for TCP wrappers (optional)
hosts.deny Host access file for TCP wrappers (optional)
hosts.equiv List of trusted hosts for rlogin, rsh, rcp (optional)
hosts.lpd List of trusted hosts for lpd (optional)
inetd.conf Configuration file for inetd (optional)
inittab Configuration file for init (optional)
issue Pre-login message and identification file (optional)
ld.so.conf List of extra directories to search for shared libraries
(optional)
motd Post-login message of the day file (optional)
mtab Dynamic information about filesystems (optional)
mtools.conf Configuration file for mtools (optional)
networks Static information about network names (optional)
passwd The password file (optional)
printcap The lpd printer capability database (optional)
profile Systemwide initialization file for sh shell logins (optional)
protocols IP protocol listing (optional)
resolv.conf Resolver configuration file (optional)
rpc RPC protocol listing (optional)
securetty TTY access control for root login (optional)
services Port names for network services (optional)
shells Pathnames of valid login shells (optional)
syslog.conf Configuration file for syslogd (optional)
mtab does not fit the static nature of /etc: it is excepted for historical
reasons. On some Linux systems, this may be a symbolic link to /proc/mounts,
in which case this exception is not required.
/etc/opt : Configuration files for /opt
Host-specific configuration files for add-on application software packages
must be installed within the directory /etc/opt/&60;subdir&62;, where
&60;subdir&62; is the name of the subtree in /opt where the static data
from that package is stored.
No structure is imposed on the internal arrangement of /etc/opt/&60;subdir&62;.
If a configuration file must reside in a different location in order for the
package or system to function properly, it may be placed in a location other
than /etc/opt/&60;subdir&62;.
The rationale behind this subtree is best explained by refering to the
rationale for /opt.
/etc/X11 : Configuration for the X Window System (optional)
/etc/X11 is the location for all X11 host-specific configuration. This
directory is necessary to allow local control if /usr is mounted read only.
The following files, or symbolic links to files, must be in /etc/X11 if the
corresponding subsystem is installed:
Xconfig The configuration file for early versions of XFree86 (optional)
XF86Config The configuration file for XFree86 versions 3 and 4 (optional)
Xmodmap Global X11 keyboard modification file (optional)
Subdirectories of /etc/X11 may include those for xdm and for any other
programs (some window managers, for example) that need them.
/etc/X11/xdm holds the configuration files for xdm. These are most of the
files previously found in /usr/lib/X11/xdm. Some local variable data for
xdm is stored in /var/lib/xdm.
It is recommended that window managers with only one configuration file
which is a default .*wmrc file must name it system.*wmrc (unless there is
a widely-accepted alternative name) and not use a subdirectory. Any window
manager subdirectories must be identically named to the actual window
manager binary.
/etc/sgml : Configuration files for SGML (optional)
Generic configuration files defining high-level parameters of the SGML
systems are installed here. Files with names *.conf indicate generic
configuration files. File with names *.cat are the DTD-specific centralized
catalogs, containing references to all other catalogs needed to use the
given DTD. The super catalog file catalog references all the centralized
catalogs.
/etc/xml : Configuration files for XML (optional)
Generic configuration files defining high-level parameters of the XML
systems are installed here. Files with names *.conf indicate generic
configuration files. The super catalog file catalog references all the
centralized catalogs.
|
1.7. /home
Linux is a multi-user environment so each user is also
assigned a specific directory that is accessible only to them
and the system administrator. These are the user home directories,
which can be found under '/home/$USER' (~/). It is your playground:
everything is at your command, you can write files, delete them,
install programs, etc.... Your home directory contains your
personal configuration files, the so-called dot files (their name
is preceded by a dot). Personal configuration files are usually 'hidden',
if you want to see them, you either have to turn on the appropriate
option in your file manager or run ls with the -a switch. If there is
a conflict between personal and system wide configuration files, the
settings in the personal file will prevail.
Dotfiles most likely to be altered by the end user are probably
your .xsession and .bashrc files. The configuration files for X and
Bash respectively. They allow you to be able to change the window
manager to be startup upon login and also aliases, user-specified
commands and environment variables respectively. Almost always when a
user is created their dotfiles will be taken from the /etc/skel directory
where system administrators place a sample file that user's can modify to
their hearts content.
/home can get quite large and can be used for storing downloads,
compiling, installing and running programs, your mail, your collection
of image or sound files etc.
The FSSTND states that:
/home is a fairly standard concept, but it is clearly a site-specific
filesystem.
Different people prefer to place user accounts in a variety of places.
This section describes only a suggested placement for user home
directories; nevertheless we recommend that all FHS-compliant
distributions use this as the default location for home directories.
On small systems, each user's directory is typically one of the many
subdirectories of /home such as /home/smith, /home/torvalds,
/home/operator, etc. On large systems (especially when the /home
directories are shared amongst many hosts using NFS) it is useful
to subdivide user home directories. Subdivision may be accomplished by
using subdirectories such as /home/staff, /home/guests, /home/students,
etc.
The setup will differ from host to host. Therefore, no program
should rely on this location.
If you want to find out a user's home directory, you should use the
getpwent(3) library function rather than relying on /etc/passwd because
user information may be stored remotely using systems such as NIS.
User specific configuration files for applications are stored in the
user's home directory in a file that starts with the '.' character
(a "dot file"). If an application needs to create more than one dot
file then they should be placed in a subdirectory with a name starting
with a '.' character, (a "dot directory"). In this case the
configuration files should not start with the '.' character.
It is recommended that apart from autosave and lock files programs
should refrain from creating non dot files or directories in a home
directory without user intervention.
|
1.8. /initrd
initrd provides the capability to load a RAM disk by the boot
loader. This RAM disk can then be mounted as the root file
system and programs can be run from it. Afterwards, a new
root file system can be mounted from a different device. The
previous root (from initrd) is then moved to a directory and
can be subsequently unmounted.
initrd is mainly designed to allow system startup to occur
in two phases, where the kernel comes up with a minimum set
of compiled-in drivers, and where additional modules are
loaded from initrd.
Operation
---------
When using initrd, the system typically boots as follows:
1) the boot loader loads the kernel and the initial RAM disk
2) the kernel converts initrd into a "normal" RAM disk and
frees the memory used by initrd
3) initrd is mounted read-write as root
4) /linuxrc is executed (this can be any valid executable,
including shell scripts; it is run with uid 0 and can do
basically everything init can do)
5) linuxrc mounts the "real" root file system
6) linuxrc places the root file system at the root directory
using the pivot_root system call
7) the usual boot sequence (e.g. invocation of /sbin/init) is
performed on the root file system
8) the initrd file system is removed
Note that changing the root directory does not involve unmounting
it. It is therefore possible to leave processes running on initrd
during that procedure. Also note that file systems mounted under
initrd continue to be accessible.
Usage scenarios
---------------
The main motivation for implementing initrd was to allow
for modular kernel configuration at system installation.
The procedure would work as follows:
1) system boots from floppy or other media with a minimal kernel
(e.g. support for RAM disks, initrd, a.out, and the Ext2 FS)
and loads initrd
2) /linuxrc determines what is needed to (1) mount the "real" root
FS (i.e. device type, device drivers, file system) and (2) the
distribution media (e.g. CD-ROM, network, tape, ...). This can
be done by asking the user, by auto-probing, or by using a
hybrid approach.
3) /linuxrc loads the necessary kernel modules
4) /linuxrc creates and populates the root file system (this
doesn't have to be a very usable system yet)
5) /linuxrc invokes pivot_root to change the root file system and
execs - via chroot - a program that continues the installation
6) the boot loader is installed
7) the boot loader is configured to load an initrd with the set of
modules that was used to bring up the system (e.g. /initrd can
be modified, then unmounted, and finally, the image is written
from /dev/ram0 or /dev/rd/0 to a file)
8) now the system is bootable and additional installation tasks
can be performed
The key role of initrd here is to re-use the configuration data
during normal system operation without requiring the use of a
bloated "generic" kernel or re-compiling or re-linking the kernel.
A second scenario is for installations where Linux runs on systems
with different hardware configurations in a single administrative
domain. In such cases, it is desirable to generate only a small set
of kernels (ideally only one) and to keep the system-specific part
of configuration information as small as possible. In this case, a
common initrd could be generated with all the necessary modules.
Then, only /linuxrc or a file read by it would have to be different.
A third scenario are more convenient recovery disks, because
information like the location of the root FS partition doesn't have
to be provided at boot time, but the system loaded from initrd can
invoke a user-friendly dialog and it can also perform some sanity
checks (or even some form of auto-detection).
Last not least, CD-ROM distributors may use it for better installation
from CD, e.g. by using a boot floppy and bootstrapping a bigger RAM disk
via initrd from CD; or by booting via a loader like LOADLIN or directly
from the CD-ROM, and loading the RAM disk from CD without need of floppies.
|
1.9. /lib
The /lib directory contains kernel modules and those shared library
images (the C programming code library) needed to boot the system and
run the commands in the root filesystem, ie. by binaries in /bin and
/sbin. Libraries are readily identifiable through their filename
extension of *.so. Windows equivalent to a shared library would be a DLL
(dynamically linked library) file. They are essential for basic system
functionality. Kernel modules (drivers) are in the subdirectory
/lib/modules/'kernel-version'. To ensure proper module compilation you
should ensure that /lib/modules/'kernel-version'/kernel/build points to
/usr/src/'kernel-version' or ensure that the Makefile knows where the
kernel source itself are located.
- /lib/'machine-architecture'
- Contains platform/architecture dependent libraries.
- /lib/iptables
- iptables shared library files.
- /lib/kbd
- Contains various keymaps.
- /lib/modules/'kernel-version'
- The home of all the kernel modules. The organisation of
files here is reasonably clear so no requires no elaboration.
- /lib/modules/'kernel-version'/isapnpmap.dep
-
has details on ISA based cards, the modules that they
require and various other attributes.
- /lib/modules/'kernel-version'/modules.dep
-
lists all modules dependencies. This file can
be updated using the depmod command.
- /lib/modules/'kernel-version'/pcimap
- is the PCI equivalent of the
/lib/modules/'kernel-version'/isapnpmap.dep file.
- /lib/modules/'kernel-version'/usbmap
- is the USB equivalent of the
/lib/modules/'kernel-version'/isapnpmap.dep file.
- /lib/oss
-
All OSS (Open Sound System) files are installed
here by default.
- /lib/security
- PAM library files.
The FSSTND states that the /lib directory contains those shared library
images needed to boot the system and run the commands in the root filesystem,
ie. by binaries in /bin and /sbin.
Shared libraries that are only necessary for binaries in /usr (such as any
X Window binaries) must not be in /lib. Only the shared libraries required
to run binaries in /bin and /sbin may be here. In particular, the library
libm.so.* may also be placed in /usr/lib if it is not required by anything
in /bin or /sbin.
At least one of each of the following filename patterns are required (they
may be files, or symbolic links):
libc.so.* The dynamically-linked C library (optional)
ld* The execution time linker/loader (optional)
If a C preprocessor is installed, /lib/cpp must be a reference to it, for
historical reasons. The usual placement of this binary is /usr/bin/cpp.
The following directories, or symbolic links to directories, must be in
/lib, if the corresponding subsystem is installed:
modules Loadable kernel modules (optional)
/lib<qual> : Alternate format essential shared libraries (optional)
There may be one or more variants of the /lib directory on systems which
support more than one binary format requiring separate libraries.
This is commonly used for 64-bit or 32-bit support on systems which support
multiple binary formats, but require libraries of the same name. In this
case, /lib32 and /lib64 might be the library directories, and /lib a symlink
to one of them.
If one or more of these directories exist, the requirements for their contents
are the same as the normal /lib directory, except that /lib<qual>/cpp is
not required.
/lib<qual>/cpp is still permitted: this allows the case where /lib and
/lib<qual> are the same (one is a symbolic link to the other).
|
1.10. /lost+found
As was explained earlier during the overview of the FSSTND, Linux should
always go through a proper shutdown. Sometimes your system might crash
or a power failure might take the machine down. Either way, at the next
boot, a lengthy filesystem check (the speed of this check is dependent on
the type of filesystem that you actually use. ie. ext3 is faster than ext2
because it is a journalled filesystem) using fsck will be done. Fsck will
go through the system and try to recover any corrupt files that it finds.
The result of this recovery operation will be placed in this directory.
The files recovered are not likely to be complete or make much sense but
there always is a chance that something worthwhile is recovered. Each
partition has its own lost+found directory. If you find files in there,
try to move them back to their original location. If you find something
like a broken symbolic link to 'file', you have to reinstall the file/s
from the corresponding RPM, since your file system got damaged so badly
that the files were mutilated beyond recognition. Below is an example of
a /lost+found directory. As you can see, the vast majority of files
contained here are in actual fact sockets. As for the rest of the other
files they were found to be damaged system files and personal files.
These files were not able to be recovered.
total 368
-rw-r--r-- 1 root root 110891 Oct 5 14:14 #388200
-rw-r--r-- 1 root root 215 Oct 5 14:14 #388201
-rw-r--r-- 1 root root 110303 Oct 6 23:09 #388813
-rw-r--r-- 1 root root 141 Oct 6 23:09 #388814
-rw-r--r-- 1 root root 110604 Oct 6 23:09 #388815a
-rw-r--r-- 1 root root 194 Oct 6 23:09 #388816
srwxr-xr-x 1 root root 0 Oct 6 13:00 #51430
srwxr-xr-x 1 root root 0 Oct 6 00:23 #51433
-rw------- 1 root root 63 Oct 6 00:23 #51434
srwxr-xr-x 1 root root 0 Oct 6 13:00 #51436
srwxrwxrwx 1 root root 0 Oct 6 00:23 #51437
srwx------ 1 root root 0 Oct 6 00:23 #51438
-rw------- 1 root root 63 Oct 6 13:00 #51439
srwxrwxrwx 1 root root 0 Oct 6 13:00 #51440
srwx------ 1 root root 0 Oct 6 13:00 #51442
-rw------- 1 root root 63 Oct 6 23:09 #51443
srwx------ 1 root root 0 Oct 6 10:40 #51445
srwxrwxrwx 1 root root 0 Oct 6 23:09 #51446
srwx------ 1 root root 0 Oct 6 23:09 #51448
|
1.11. /media
Amid much controversy and consternation on the part of system and
network administrators a directory containing mount points for removable
media has now been created. Funnily enough, it has been named /media.
This directory contains subdirectories which are used as mount points for
removeable media such as floppy disks, cdroms and zip disks.
The motivation for the creation of this directory has been that historically
there have been a number of other different places used to mount removeable
media such as /cdrom, /mnt or /mnt/cdrom. Placing the mount points for all
removeable media directly in the root directory would potentially result in
a large number of extra directories in /. Although the use of subdirectories
in /mnt as a mount point has recently been common, it conflicts with a much
older tradition of using /mnt directly as a temporary mount point.
The following directories, or symbolic links to directories, must be in /media,
if the corresponding subsystem is installed:
floppy Floppy drive (optional)
cdrom CD-ROM drive (optional)
cdrecorder CD writer (optional)
zip Zip drive (optional)
On systems where more than one device exists for mounting a certain type of
media, mount directories can be created by appending a digit to the name of
those available above starting with '0', but the unqualified name must also
exist.
A compliant implementation with two CDROM drives might have /media/cdrom0
and /media/cdrom1 with /media/cdrom a symlink to either of these.
|
Please see the section on the /mnt directory to achieve a better understanding
of the process on mounting and unmounting filesystems.
1.12. /mnt
This is a generic mount point under which you mount your filesystems
or devices. Mounting is the process by which you make a filesystem available
to the system. After mounting your files will be accessible under the
mount-point. This directory usually contains mount points or sub-directories
where you mount your floppy and your CD. You can also create additional
mount-points here if you wish. Standard mount points would include
/mnt/cdrom and /mnt/floppy. There is no limitation to creating a mount-point
anywhere on your system but by convention and for sheer practicality do not
litter your file system with mount-points. It should be noted that some
distributions like Debian allocate /floppy and /cdrom as mount points while
Redhat and Mandrake puts them in /mnt/floppy and /mnt/cdrom respectively.
However, it should be noted that as of FSSTND version 2.3 the purpose of this
directory has changed.
This directory is provided so that the system administrator may temporarily
mount a filesystem as needed. The content of this directory is a local issue
and should not affect the manner in which any program is run.
This directory must not be used by installation programs: a suitable temporary
directory not in use by the system must be used instead.
|
1.12.1. Mounting and unmounting
Before one can use a filesystem, it has to be mounted.
The operating system then does various bookkeeping things to make sure that
everything works. Since all files in UNIX are in a single directory tree,
the mount operation will make it look like the contents of the new
filesystem are the contents of an existing subdirectory in some already
mounted filesystem.
The mounts could be done as in the
following example:
$ mount /dev/hda2 /home
$ mount /dev/hda3 /usr
$
|
The mount command takes two
arguments. The first one is the device file corresponding to the disk or
partition containing the filesystem. The second one is the directory below
which it will be mounted. After these commands the contents of the two
filesystems look just like the contents of the /home
and /usr directories, respectively. One would then say
that `` /dev/hda2 is mounted on
/home'', and similarly for
/usr. To look at either filesystem, one would look at
the contents of the directory on which it has been mounted, just as if it
were any other directory. Note the difference between the device file,
/dev/hda2, and the mounted-on directory,
/home. The device file gives access to the raw contents
of the disk, the mounted-on directory gives access to the files on the disk.
The mounted-on directory is called the mount point.
Linux supports many filesystem types. mount tries
to guess the type of the filesystem. You can also use the -t fstype
option to specify the type directly; this is sometimes necessary, since the
heuristics mount uses do not always work. For example, to
mount an MS-DOS floppy, you could use the following command:
$ mount -t msdos /dev/fd0 /floppy
$
|
The mounted-on directory need not be empty,
although it must exist. Any files in it, however, will be inaccessible by
name while the filesystem is mounted. (Any files that have already been
opened will still be accessible. Files that have hard links from other
directories can be accessed using those names.) There is no harm done with
this, and it can even be useful. For instance, some people like to have
/tmp and /var/tmp synonymous, and
make /tmp be a symbolic link to /var/tmp.
When the system is booted, before the /var filesystem
is mounted, a /var/tmp directory residing on the root
filesystem is used instead. When /var is mounted, it
will make the /var/tmp directory on the root filesystem
inaccessible. If /var/tmp didn't exist on the root
filesystem, it would be impossible to use temporary files before mounting
/var.
If you don't intend to write
anything to the filesystem, use the -r switch for
mount to do a read-only mount.
This will make the kernel stop any attempts at writing to the filesystem,
and will also stop the kernel from updating file access times in the inodes.
Read-only mounts are necessary for unwritable media, e.g., CD-ROMs.
The alert reader has already noticed a slight logistical problem. How
is the first filesystem (called the root filesystem,
because it contains the root directory) mounted, since it obviously
can't be mounted on another filesystem? Well, the answer is that it is
done by magic.
For more information, see the kernel source or
the Kernel Hackers' Guide.
The root filesystem is
magically mounted at boot time, and one can rely on it to always be mounted.
If the root filesystem can't be mounted, the system does not boot. The
name of the filesystem that is magically mounted as root is either compiled
into the kernel, or set using LILO or rdev.
The root filesystem is usually first mounted read-only. The startup
scripts will then run fsck to verify its validity, and if
there are no problems, they will re-mount it so that
writes will also be allowed. fsck must not be run on a
mounted filesystem, since any changes to the filesystem while
fsck is running will cause trouble.
Since the root filesystem is mounted read-only while it is being checked,
fsck can fix any problems without worry, since the
remount operation will flush any metadata that the filesystem keeps in
memory.
On many systems there are other filesystems that should
also be mounted automatically at boot time. These are specified in the
/etc/fstab file; see the fstab man page for details on
the format. The details of exactly when the extra filesystems are mounted
depend on many factors, and can be configured by each administrator if need
be.
When a filesystem no longer needs to be mounted, it can be
unmounted with umount.
It should of course
be unmount, but the n mysteriously disappeared in the
70s, and hasn't been seen since. Please return it to Bell Labs, NJ, if
you find it.
umount takes one argument:
either the device file or the mount point. For example, to unmount the
directories of the previous example, one could use the commands
$ umount /dev/hda2
$ umount /usr
$
|
See the man page for further instructions on how to use the command.
It is imperative that you always unmount a mounted floppy.
Don't just pop the floppy out of the drive! Because
of disk caching, the data is not necessarily written to the floppy until you
unmount it, so removing the floppy from the drive too early might cause the
contents to become garbled. If you only read from the floppy, this is not
very likely, but if you write, even accidentally, the result may be
catastrophic.
Mounting and unmounting requires super user
privileges, i.e., only root can do it. The reason for this is that if any
user can mount a floppy on any directory, then it is rather easy to create a
floppy with, say, a Trojan horse disguised as /bin/sh,
or any other often used program. However, it is often necessary to allow
users to use floppies, and there are several ways to do this:
- Give the users the root password. This is
obviously bad security, but is the easiest solution. It works well if there
is no need for security anyway, which is the case on many non-networked,
personal systems.
- Use a program such as
sudo to allow users to use mount. This is still bad
security, but doesn't directly give super user privileges to everyone.
- Make the users use mtools, a package for
manipulating MS-DOS filesystems, without mounting them. This works well if
MS-DOS floppies are all that is needed, but is rather awkward otherwise.
- List the floppy devices and their
allowable mount points together with the suitable options in
/etc/fstab.
The last
alternative can be implemented by adding a line like the following to the
/etc/fstab file:
/dev/fd0 /floppy
msdos user,noauto 0 0
|
The columns are: device file to
mount, directory to mount on, filesystem type, options, backup frequency
(used by dump), and fsck pass number
(to specify the order in which filesystems should be checked upon boot; 0
means no check).
The noauto option stops this
mount to be done automatically when the system is started (i.e., it stops
mount -a from mounting it). The user
option allows any user to mount the filesystem, and, because of security
reasons, disallows execution of programs (normal or setuid) and
interpretation of device files from the mounted filesystem. After this, any
user can mount a floppy with an msdos filesystem with the following command:
The floppy can (and needs to, of course) be
unmounted with the corresponding umount command.
If you want to provide access to several types of floppies, you need
to give several mount points. The settings can be different for each mount
point. For example, to give access to both MS-DOS and ext2 floppies, you
could have the following to lines in /etc/fstab:
/dev/fd0 /dosfloppy msdos user,noauto 0 0 /dev/fd0
/ext2floppy ext2 user,noauto 0 0
|
For MS-DOS
filesystems (not just floppies), you probably want to restrict access to it
by using the uid, gid, and
umask filesystem options, described in detail on the
mount manual page. If you aren't careful, mounting an
MS-DOS filesystem gives everyone at least read access to the files in it,
which is not a good idea.
1.13. /opt
This directory is reserved for all the software and add-on packages
that are not part of the default installation. For example, StarOffice,
Kylix, Netscape Communicator and WordPerfect packages are normally
found here. To comply with the FSSTND, all third party applications
should be installed in this directory. Any package to be installed
here must locate its static files (ie. extra fonts, clipart, database
files) must locate its static files in a separate /opt/'package'
or /opt/'provider' directory tree (similar to the way in which Windows
will install new software to its own directory tree
C:\Windows\Progam Files\"Program Name"), where 'package' is a name that
describes the software package and 'provider' is the provider's LANANA
registered name.
Although most distributions neglect to create the directories /opt/bin,
/opt/doc, /opt/include, /opt/info, /opt/lib, and /opt/man they are
reserved for local system administrator use. Packages may provide
"front-end" files intended to be placed in (by linking or copying)
these reserved directories by the system administrator, but must function
normally in the absence of these reserved directories. Programs to be
invoked by users are located in the directory /opt/'package'/bin. If
the package includes UNIX manual pages, they are located in /opt/'package'/man
and the same substructure as /usr/share/man must be used. Package files
that are variable must be installed in /var/opt. Host-specific
configuration files are installed in /etc/opt.
Under no circumstances are other package files to exist outside
the /opt, /var/opt, and /etc/opt hierarchies except for those package
files that must reside in specific locations within the filesystem tree
in order to function properly. For example, device lock files in /var/lock
and devices in /dev. Distributions may install software in /opt, but must
not modify or delete software installed by the local system administrator
without the assent of the local system administrator.
The use of /opt for add-on software is a well-established practice
in the UNIX community. The System V Application Binary Interface
[AT&T 1990], based on the System V Interface Definition (Third Edition)
and the Intel Binary Compatibility Standard v. 2 (iBCS2) provides for an
/opt structure very similar to the one defined here.
Generally, all data required to support a package on a system
must be present within /opt/'package', including files intended
to be copied into /etc/opt/'package' and /var/opt/'package'
as well as reserved directories in /opt. The minor restrictions on
distributions using /opt are necessary because conflicts are possible
between distribution installed and locally installed software, especially
in the case of fixed pathnames found in some binary software.
The structure of the directories below /opt/'provider' is left up to the
packager of the software, though it is recommended that packages are
installed in /opt/'provider'/'package' and follow a similar structure to
the guidelines for /opt/package. A valid reason for diverging from this
structure is for support packages which may have files installed in /opt/
'provider'/lib or /opt/'provider'/bin.
1.14. /proc
/proc is very special in that it is also a virtual filesystem.
It's sometimes referred to as a process information pseudo-file system.
It doesn't contain 'real' files but runtime system information
(e.g. system memory, devices mounted, hardware configuration, etc). For this
reason it can be regarded as a control and information centre for the
kernel. In fact, quite a lot of system utilities are simply calls to files
in this directory. For example, 'lsmod' is the same as 'cat
/proc/modules' while 'lspci' is a synonym for 'cat
/proc/pci'. By altering files located in this directory you can even
read/change kernel parameters (sysctl) while the system is running.
The most distinctive thing about files in this directory is the fact
that all of them have a file size of 0, with the exception of kcore, mtrr
and self. A directory listing looks similar to the following:
total 525256
dr-xr-xr-x 3 root root 0 Jan 19 15:00 1
dr-xr-xr-x 3 daemon root 0 Jan 19 15:00 109
dr-xr-xr-x 3 root root 0 Jan 19 15:00 170
dr-xr-xr-x 3 root root 0 Jan 19 15:00 173
dr-xr-xr-x 3 root root 0 Jan 19 15:00 178
dr-xr-xr-x 3 root root 0 Jan 19 15:00 2
dr-xr-xr-x 3 root root 0 Jan 19 15:00 3
dr-xr-xr-x 3 root root 0 Jan 19 15:00 4
dr-xr-xr-x 3 root root 0 Jan 19 15:00 421
dr-xr-xr-x 3 root root 0 Jan 19 15:00 425
dr-xr-xr-x 3 root root 0 Jan 19 15:00 433
dr-xr-xr-x 3 root root 0 Jan 19 15:00 439
dr-xr-xr-x 3 root root 0 Jan 19 15:00 444
dr-xr-xr-x 3 daemon daemon 0 Jan 19 15:00 446
dr-xr-xr-x 3 root root 0 Jan 19 15:00 449
dr-xr-xr-x 3 root root 0 Jan 19 15:00 453
dr-xr-xr-x 3 root root 0 Jan 19 15:00 456
dr-xr-xr-x 3 root root 0 Jan 19 15:00 458
dr-xr-xr-x 3 root root 0 Jan 19 15:00 462
dr-xr-xr-x 3 root root 0 Jan 19 15:00 463
dr-xr-xr-x 3 root root 0 Jan 19 15:00 464
dr-xr-xr-x 3 root root 0 Jan 19 15:00 465
dr-xr-xr-x 3 root root 0 Jan 19 15:00 466
dr-xr-xr-x 3 root root 0 Jan 19 15:00 467
dr-xr-xr-x 3 gdm gdm 0 Jan 19 15:00 472
dr-xr-xr-x 3 root root 0 Jan 19 15:00 483
dr-xr-xr-x 3 root root 0 Jan 19 15:00 5
dr-xr-xr-x 3 root root 0 Jan 19 15:00 6
dr-xr-xr-x 3 root root 0 Jan 19 15:00 7
dr-xr-xr-x 3 root root 0 Jan 19 15:00 8
-r--r--r-- 1 root root 0 Jan 19 15:00 apm
dr-xr-xr-x 3 root root 0 Jan 19 15:00 bus
-r--r--r-- 1 root root 0 Jan 19 15:00 cmdline
-r--r--r-- 1 root root 0 Jan 19 15:00 cpuinfo
-r--r--r-- 1 root root 0 Jan 19 15:00 devices
-r--r--r-- 1 root root 0 Jan 19 15:00 dma
dr-xr-xr-x 3 root root 0 Jan 19 15:00 driver
-r--r--r-- 1 root root 0 Jan 19 15:00 execdomains
-r--r--r-- 1 root root 0 Jan 19 15:00 fb
-r--r--r-- 1 root root 0 Jan 19 15:00 filesystems
dr-xr-xr-x 2 root root 0 Jan 19 15:00 fs
dr-xr-xr-x 4 root root 0 Jan 19 15:00 ide
-r--r--r-- 1 root root 0 Jan 19 15:00 interrupts
-r--r--r-- 1 root root 0 Jan 19 15:00 iomem
-r--r--r-- 1 root root 0 Jan 19 15:00 ioports
dr-xr-xr-x 18 root root 0 Jan 19 15:00 irq
-r-------- 1 root root 536809472 Jan 19 15:00 kcore
-r-------- 1 root root 0 Jan 19 14:58 kmsg
-r--r--r-- 1 root root 0 Jan 19 15:00 ksyms
-r--r--r-- 1 root root 0 Jan 19 15:00 loadavg
-r--r--r-- 1 root root 0 Jan 19 15:00 locks
-r--r--r-- 1 root root 0 Jan 19 15:00 mdstat
-r--r--r-- 1 root root 0 Jan 19 15:00 meminfo
-r--r--r-- 1 root root 0 Jan 19 15:00 misc
-r--r--r-- 1 root root 0 Jan 19 15:00 modules
-r--r--r-- 1 root root 0 Jan 19 15:00 mounts
-rw-r--r-- 1 root root 137 Jan 19 14:59 mtrr
dr-xr-xr-x 3 root root 0 Jan 19 15:00 net
dr-xr-xr-x 2 root root 0 Jan 19 15:00 nv
-r--r--r-- 1 root root 0 Jan 19 15:00 partitions
-r--r--r-- 1 root root 0 Jan 19 15:00 pci
dr-xr-xr-x 4 root root 0 Jan 19 15:00 scsi
lrwxrwxrwx 1 root root 64 Jan 19 14:58 self -> 483
-rw-r--r-- 1 root root 0 Jan 19 15:00 slabinfo
-r--r--r-- 1 root root 0 Jan 19 15:00 stat
-r--r--r-- 1 root root 0 Jan 19 15:00 swaps
dr-xr-xr-x 10 root root 0 Jan 19 15:00 sys
dr-xr-xr-x 2 root root 0 Jan 19 15:00 sysvipc
dr-xr-xr-x 4 root root 0 Jan 19 15:00 tty
-r--r--r-- 1 root root 0 Jan 19 15:00 uptime
-r--r--r-- 1 root root 0 Jan 19 15:00 version
|
Each of the numbered directories corresponds to an actual process ID.
Looking at the process table, you can match processes with the associated
process ID. For example, the process table might indicate the following for
the secure shell server:
# ps ax | grep sshd
439 ? S 0:00 /usr/sbin/sshd
|
Details of this process can be obtained by looking at the associated
files in the directory for this process, /proc/460. You might wonder how you
can see details of a process that has a file size of 0. It makes more sense
if you think of it as a window into the kernel. The file doesn't
actually contain any data; it just acts as a pointer to where the actual
process information resides. For example, a listing of the files in the
/proc/460 directory looks similar to the following:
total 0
-r--r--r-- 1 root root 0 Jan 19 15:02 cmdline
lrwxrwxrwx 1 root root 0 Jan 19 15:02 cwd -> /
-r-------- 1 root root 0 Jan 19 15:02 environ
lrwxrwxrwx 1 root root 0 Jan 19 15:02 exe -> /usr/sbin/sshd
dr-x------ 2 root root 0 Jan 19 15:02 fd
-r--r--r-- 1 root root 0 Jan 19 15:02 maps
-rw------- 1 root root 0 Jan 19 15:02 mem
lrwxrwxrwx 1 root root 0 Jan 19 15:02 root -> /
-r--r--r-- 1 root root 0 Jan 19 15:02 stat
-r--r--r-- 1 root root 0 Jan 19 15:02 statm
-r--r--r-- 1 root root 0 Jan 19 15:02 status
|
The purpose and contents of each of these files is explained below:
- /proc/PID/cmdline
- Command
line arguments.
- /proc/PID/cpu
- Current
and last cpu in which it was executed.
- /proc/PID/cwd
- Link
to the current working directory.
- /proc/PID/environ
- Values
of environment variables.
- /proc/PID/exe
- Link
to the executable of this process.
- /proc/PID/fd
- Directory,
which contains all file descriptors.
- /proc/PID/maps
- Memory
maps to executables and library files.
- /proc/PID/mem
- Memory
held by this process.
- /proc/PID/root
- Link
to the root directory of this process.
- /proc/PID/stat
- Process
status.
- /proc/PID/statm
- Process
memory status information.
- /proc/PID/status
- Process
status in human readable form.
Should you wish to know more, the man page for proc describes each of
the files associated with a running process ID in far greater detail.
Even though files appear to be of size 0, examining their contents
reveals otherwise:
Name: sshd
State: S (sleeping)
Tgid: 439
Pid: 439
PPid: 1
TracerPid: 0
Uid: 0 0 0 0
Gid: 0 0 0 0
FDSize: 32
Groups:
VmSize: 2788 kB
VmLck: 0 kB
VmRSS: 1280 kB
VmData: 252 kB
VmStk: 16 kB
VmExe: 268 kB
VmLib: 2132 kB
SigPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 8000000000001000
SigCgt: 0000000000014005
CapInh: 0000000000000000
CapPrm: 00000000fffffeff
CapEff: 00000000fffffeff
|
The files in the /proc directory act very similar to the process ID
subdirectory files. For example, examining the contents of the
/proc/interrupts file displays something like the following:
CPU0
0: 32657 XT-PIC timer
1: 1063 XT-PIC keyboard
2: 0 XT-PIC cascade
8: 3 XT-PIC rtc
9: 0 XT-PIC cmpci
11: 332 XT-PIC nvidia
14: 5289 XT-PIC ide0
15: 13 XT-PIC ide1
NMI: 0
ERR: 0
|
Each of the numbers down the left-hand column represents the interrupt
that is in use. Examining the contents of the file dynamically gathers the
associated data and displays it to the screen. Most of the /proc file system
is read-only; however, some files allow kernel variable to be changed. This
provides a mechanism to actually tune the kernel without recompiling and
rebooting.
The procinfo utility summarizes /proc file system information into a
display similar to the following:
Linux 2.4.18 (root@DEB) (gcc 2.95.4 20011002 ) #2 1CPU [DEB.(none)]
Memory: Total Used Free Shared Buffers Cached
Mem: 513908 107404 406504 0 2832 82180
Swap: 265032 0 265032
Bootup: Sun Jan 19 14:58:27 2003 Load average: 0.29 0.13 0.05 1/30 566
user : 0:00:10.26 2.3% page in : 74545 disk 1: 6459r 796w
nice : 0:00:00.00 0.0% page out: 9416 disk 2: 19r 0w
system: 0:00:19.55 4.5% swap in : 1
idle : 0:06:48.30 93.2% swap out: 0
uptime: 0:07:18.11 context : 22059
irq 0: 43811 timer irq 9: 0 cmpci
irq 1: 1427 keyboard irq 11: 332 nvidia
irq 2: 0 cascade [4] irq 12: 2
irq 6: 2 irq 14: 7251 ide0
irq 8: 3 rtc irq 15: 83 ide1
|
- /proc/apm
-
Advanced power management info.
- /proc/bus
- Directory containing
bus specific information.
- /proc/cmdline
- Kernel command
line.
- /proc/cpuinfo
-
Information about the processor, such as its type, make, model, and
performance.
- /proc/devices
-
List of device drivers configured into the currently running kernel (block
and character).
- /proc/dma
- Shows which DMA
channels are being used at the moment.
- /proc/driver
- Various drivers
grouped here, currently rtc
- /proc/execdomains
- Execdomains,
related to security.
- /proc/fb
- Frame Buffer devices.
- /proc/filesystems
- Filesystems
configured/supported into/by the kernel.
- /proc/fs
- File system parameters,
currently nfs/exports.
- /proc/ide
- This subdirectory
contains information about all IDE devices of which the kernel is aware.
There is one subdirectory for each IDE controller, the file drivers and a
link for each IDE device, pointing to the device directory in the
controller-specific subtree. The file drivers contains general information
about the drivers used for the IDE devices. More detailed information can be
found in the controller-specific subdirectories. These are named ide0, ide1
and so on. Each of these directories contains the files shown here:
- /proc/ide/ide?/channel
- IDE
channel (0 or 1)
- /proc/ide/ide?/config
-
Configuration (only for PCI/IDE bridge)
- /proc/ide/ide?/mate
- Mate name
(onchip partnered controller)
- /proc/ide/ide?/model
- Type/Chipset
of IDE controller
-
Each device connected to a controller has a separate subdirectory in the controllers
directory. The following files listed are contained in these directories:
- /proc/ide/ide?/model/cache
-
The cache.
- /proc/ide/ide?/model/capacity
-
Capacity of the medium (in 512Byte blocks)
- /proc/ide/ide?/model/driver
-
driver and version
- /proc/ide/ide?/model/geometry
-
physical and logical geometry
- /proc/ide/ide?/model/identify
-
device identify block
- /proc/ide/ide?/model/media
- media
type
- /proc/ide/ide?/model/model
-
device identifier
- /proc/ide/ide?/model/settings
-
device setup
- /proc/ide/ide?/model/smart_thresholds
-
IDE disk management thresholds
- /proc/ide/ide?/model/smart_values
-
IDE disk management values
- /proc/interrupts
- Shows which
interrupts are in use, and how many of each there have been.
- You can, for example, check which interrupts are currently in use
and what they are used for by looking in the file /proc/interrupts:
CPU0 0: 8728810
XT-PIC timer 1: 895
XT-PIC keyboard 2:
0 XT-PIC cascade 3: 531695
XT-PIC aha152x 4: 2014133
XT-PIC serial 5: 44401
XT-PIC pcnet_cs 8: 2
XT-PIC rtc 11: 8
XT-PIC i82365 12: 182918
XT-PIC PS/2 Mouse 13: 1
XT-PIC fpu 14: 1232265
XT-PIC ide0 15: 7
XT-PIC ide1 NMI: 0
|
- In 2.4 based kernels a couple of
lines were added to this file LOC & ERR (this is the output of an SMP
machine):
-
CPU0 CPU1
0: 1243498 1214548 IO-APIC-edge timer
1: 8949 8958 IO-APIC-edge keyboard
2: 0 0 XT-PIC cascade
5: 11286 10161 IO-APIC-edge soundblaster
8: 1 0 IO-APIC-edge rtc
9: 27422 27407 IO-APIC-edge 3c503
12: 113645 113873 IO-APIC-edge PS/2 Mouse
13: 0 0 XT-PIC fpu 14: 22491 24012 IO-APIC-edge ide0
15: 2183 2415 IO-APIC-edge ide1
17: 30564 30414 IO-APIC-level eth0
18: 177 164 IO-APIC-level bttv NMI: 2457961 2457959
LOC: 2457882 2457881 ERR: 2155
|
- NMI is incremented in this
case because every timer interrupt generates a NMI (Non Maskable Interrupt)
which is used by the NMI Watchdog to detect lookups.
- LOC is the
local interrupt counter of the internal APIC of every CPU.
- ERR is incremented in the case of errors in the IO-APIC bus (the bus
that connects the CPUs in an SMP system. This means that an error has been
detected, the IO-APIC automatically retries the transmission, so it should
not be a big problem, but you should read the SMP-FAQ.
- In this
context it could be interesting to note the new irq directory in 2.4. It
could be used to set IRQ to CPU affinity, this means that you can
"hook" an IRQ to only one CPU, or to exclude a CPU from handling
IRQs. The contents of the irq subdir is one subdir for each IRQ, and one
file; prof_cpu_mask. For example,
-
# ls /proc/irq/ 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
1 11 13 15 17 19 3 5 7 9
|
-
# ls /proc/irq/0/ smp_affinity
|
- The contents of the prof_cpu_mask file and each smp_affinity file for
each IRQ is the same by default:
-
# cat /proc/irq/0/smp_affinity
ffffffff
|
- It's a bitmask, in which you can specify which CPUs can handle
the IRQ, you can set it by doing:
# echo 1 > /proc/irq/prof_cpu_mask
|
- This means that only the first CPU will handle the IRQ, but you can
also echo 5 which means that only the first and fourth CPU can handle the
IRQ. The way IRQs are routed is handled by the IO-APIC, and its Round
Robin between all the CPUs which are allowed to handle it. As usual the
kernel has more info than you and does a better job than you, so the
defaults are the best choice for almost everyone.
- /proc/iomem
- Memory map.
- /proc/ioports
- Which I/O ports are
in use at the moment.
- /proc/irq
- Masks for irq to cpu
affinity.
- /proc/isapnp
-
ISA PnP (Plug&Play) Info.
- /proc/kcore
- An image of the
physical memory of the system (can be ELF or A.OUT (deprecated in 2.4)).
This is exactly the same size as your physical memory, but does not really
take up that much memory; it is generated on the fly as programs access it.
(Remember: unless you copy it elsewhere, nothing under /proc takes up any
disk space at all.)
- /proc/kmsg
- Messages output by the
kernel. These are also routed to syslog.
- /proc/ksyms
- Kernel symbol table.
- /proc/loadavg
- The 'load
average' of the system; three indicators of how much work the system has
done during the last 1, 5 & 15 minutes.
- /proc/locks
- Kernel locks.
- /proc/meminfo
- Information about
memory usage, both physical and swap. Concatenating this file produces
similar results to using 'free' or the first few lines of
'top'.
- /proc/misc
- Miscellaneous pieces
of information. This is for information that has no real place within the
rest of the proc filesystem.
- /proc/modules
- Kernel modules
currently loaded. Typically its output is the same as that given by the
'lsmod' command.
- /proc/mounts
- Mounted filesystems
- /proc/mtrr
- Information regarding
mtrrs. (On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) may be used to control processor
access to memory ranges. This is most useful when you have a video (VGA)
card on a PCI or AGP bus. Enabling write-combining allows bus write
transfers to be combined into a larger transfer before bursting over the
PCI/AGP bus. This can increase performance of image write operations 2.5
times or more. The Cyrix 6x86, 6x86MX and M II processors have Address Range
Registers (ARRs) which provide a similar functionality to MTRRs. For these,
the ARRs are used to emulate the MTRRs. The AMD K6-2 (stepping 8 and above)
and K6-3 processors have two MTRRs. These are supported. The AMD Athlon
family provide 8 Intel style MTRRs. The Centaur C6 (WinChip) has 8 MCRs,
allowing write-combining. These are also supported. The VIA Cyrix III and
VIA C3 CPUs offer 8 Intel style MTRRs.) For more details regarding mtrr
technology see /usr/src/linux/Documentation/mtrr.txt.
- /proc/net
- Status information
about network protocols.
- IPv6 information
-
- /proc/net/udp6
-
UDP sockets (IPv6).
- /proc/net/tcp6
- TCP sockets
(IPv6).
- /proc/net/raw6
-
Raw device statistics (IPv6).
- /proc/net/igmp6
- IP multicast
addresses, which this host joined (IPv6).
- /proc/net/if_inet6
- List of IPv6
interface addresses.
- /proc/net/ipv6_route
- Kernel
routing table for IPv6.
- /proc/net/rt6_stats
- Global IPv6
routing tables statistics.
- /proc/net/sockstat6
- Socket
statistics (IPv6).
- /proc/net/snmp6
- Snmp data (IPv6).
- General Network information
-
- /proc/net/arp
-
Kernel ARP table.
- /proc/net/dev
- network devices
with statistics.
- /proc/net/dev_mcast
- the Layer2
multicast groups which a device is listening to (interface index, label,
number of references, number of bound addresses).
- /proc/net/dev_stat
- network device
status.
- /proc/net/ip_fwchains
-
Firewall chain linkage.
- /proc/net/ip_fwnames
- Firewall
chain names.
- /proc/net/ip_masq
-
Directory containing the masquerading tables.
- /proc/net/ip_masquerade
- Major
masquerading table.
- /proc/net/netstat
- Network
statistics.
- /proc/net/raw
-
raw device statistics.
- /proc/net/route
- Kernel routing
table.
- /proc/net/rpc
-
Directory containing rpc info.
- /proc/net/rt_cache
- Routing cache.
- /proc/net/snmp
- SNMP data.
- /proc/net/sockstat
- Socket
statistics.
- /proc/net/tcp
-
TCP sockets.
- /proc/net/tr_rif
-
Token ring RIF routing table.
- /proc/net/udp
- UDP sockets.
- /proc/net/unix
- UNIX domain
sockets.
- /proc/net/wireless
-
Wireless interface data (Wavelan etc).
- /proc/net/igmp
- IP multicast
addresses, which this host joined.
- /proc/net/psched
- Global packet
scheduler parameters.
- /proc/net/netlink
- List of
PF_NETLINK sockets.
- /proc/net/ip_mr_vifs
- List of
multicast virtual interfaces.
- /proc/net/ip_mr_cache
- List of
multicast routing cache.
You can use this information to see
which network devices are available in your system
and how much traffic was routed over those devices. In addition, each
Channel Bond interface has its own directory. For example, the bond0 device
will have a directory called /proc/net/bond0/. It will contain information
that is specific to that bond, such as the current slaves of the bond, the
link status of the slaves, and how many times the slaves link has failed.
- /proc/parport
-
The directory /proc/parport contains information about the parallel
ports of your system. It has one subdirectory for each port,
named after the port number (0,1,2,...).
- /proc/parport/autoprobe
-
Any IEEE-1284 device ID information that has been acquired.
- /proc/parport/devices
- list of the
device drivers using that port. A + will appear by the name of the device
currently using the port (it might not appear against any).
- /proc/parport/hardware
- Parallel
port's base address, IRQ line and DMA channel.
- /proc/parport/irq
- IRQ that
parport is using for that port. This is in a separate file to allow you to
alter it by writing a new value in (IRQ number or none).
- /proc/partitions
- Table of
partitions known to the system
- /proc/pci, /proc/bus/pci
-
Depreciated info of PCI bus.
- /proc/rtc
- Real time clock
- /proc/scsi
- If you have a SCSI
host adapter in your system, you'll find a subdirectory named after the
driver for this adapter in /proc/scsi. You'll also see a list of all
recognized SCSI devices in /proc/scsi. The directory named after the driver
has one file for each adapter found in the system. These files contain
information about the controller, including the used IRQ and the IO address
range. The amount of information shown is dependent on the adapter you use.
- /proc/self
- A symbolic link to the
process directory of the program that is looking at /proc. When two
processes look at /proc, they get different links. This is mainly a
convenience to make it easier for programs to get at their process
directory.
- /proc/slabinfo
-
The slabinfo file gives information about memory usage at the slab level.
Linux uses slab pools for memory management above page level in version 2.2.
Commonly used objects have their own slab pool (such as network buffers,
directory cache, and so on).
- /proc/stat
- Overall/various
statistics about the system, such as the number of page faults since the
system was booted.
- /proc/swaps
- Swap space
utilization
- /proc/sys
-
This is not only a source of information, it also allows you to change
parameters within the kernel without the need for recompilation or even a
system reboot. Take care when attempting this as it can both optimize your
system and also crash it. It is advisable to read both documentation and
source before actually making adjustments. The entries in /proc may change
slightly between kernel versions, so if there is any doubt review the kernel
documentation in the directory /usr/src/linux/Documentation. Under some
circumstances, you may have no alternative but to reboot the machine once an
error occurs. To change a value, simply echo the new value into the file. An
example is given below in the section on the file system data. Of course,
you need to be 'root' to do any of this. You can create your own
boot script to perform this every time your system boots.
- /proc/sys/fs
- Contains file system
data. This subdirectory contains specific file system, file handle, inode,
dentry and quota information.
- dentry-state
- Status of the
directory cache. Since directory entries are dynamically allocated and
deallocated, this file indicates the current status. It holds six values, in
which the last two are not used and are always zero. The others are listed
below:
File Content
nr_dentry Almost always zero
nr_unused Number of unused cache entries
age_limit in seconds after the entry may be
reclaimed, when memory is short want_pages internally
|
- dquot-max
-
The file dquot-max shows the maximum number of cached disk
quota entries.
- dquot-nr
-
shows the number of allocated disk quota entries and the number of
free disk quota entries. If the number of available cached disk quotas
is very low and you have a large number of simultaneous system users,
you might want to raise the limit.
- file-nr and file-max
-
The kernel allocates file handles dynamically, but doesn't
free them again at this time. The value in file-max denotes
the maximum number of file handles that the Linux kernel will allocate. When
you get a lot of error messages about running out of file handles, you might
want to raise this limit. The default value is 4096. To change it, just
write the new number into the file:
# cat /proc/sys/fs/file-max
4096
# echo 8192 > /proc/sys/fs/file-max
# cat /proc/sys/fs/file-max
8192
|
- This method of revision is useful for all customizable parameters
of the kernel - simply echo the new value to the corresponding file.
- The three values in file-nr denote the number of allocated file
handles, the number of used file handles, and the maximum number of
file handles. When the allocated file handles come close to the maximum,
but the number of actually used handles is far behind, you've
encountered a peak in your usage of file handles and you don't
need to increase the maximum.
- inode-state, inode-nr and inode-max
-
As with file handles, the kernel allocates the inode
structures dynamically, but can't free them yet.
- The value in inode-max denotes the maximum number of
inode handlers. This value should be 3 to 4 times larger than the
value in file-max, since stdin, stdout, and
network sockets also need an inode struct to handle them. If you regularly
run out of inodes, you should increase this value.
- The file inode-nr contains the first two items from inode-state,
so we'll skip to that file...
- inode-state contains three actual numbers and four dummy
values. The numbers are nr_inodes, nr_free_inodes, and preshrink (in order
of appearance).
- nr_inodes
-
Denotes the number of inodes the system has allocated. This can be
slightly more than inode-max because Linux allocates them one pageful at a time.
- nr_free_inodes
-
Represents the number of free inodes and preshrink is nonzero when nr_inodes
is greater than inode-max and the system needs to prune the inode list
instead of allocating more.
- super-nr and super-max
-
Again, super block structures are allocated by the
kernel, but not freed. The file super-max contains the maximum number of
super block handlers, where super-nr shows the number of currently allocated
ones. Every mounted file system needs a super block, so if you plan to mount
lots of file systems, you may want to increase these numbers.
- binfmt_misc
-
This handles the kernel support for miscellaneous binary formats.
binfmt_misc provides the ability to register additional binary formats to
the kernel without compiling an additional module/kernel. Therefore,
binfmt_misc needs to know magic numbers at the beginning or the filename
extension of the binary. It works by maintaining a linked list of structs
that contain a description of a binary format, including a magic with size
(or the filename extension), offset and mask, and the interpreter name. On
request it invokes the given interpreter with the original program as
argument, as binfmt_java and binfmt_em86 and binfmt_mz do. Since binfmt_misc
does not define any default binary-formats, you have to register an
additional binary-format. There are two general files in binfmt_misc and one
file per registered format. The two general files are register and status.
To register a new binary format you have to issue the command echo
:name:type:offset:magic:mask:interpreter: > /proc/sys/fs/binfmt_misc/register
with appropriate name (the name for the /proc-dir entry), offset
(defaults to 0, if omitted), magic, mask (which can be omitted,
defaults to all 0xff) and last but not least, the interpreter
that is to be invoked (for example and testing /bin/echo). Type can be M for
usual magic matching or E for filename extension matching (give extension in
place of magic). If you do a cat on the file /proc/sys/fs/binfmt_misc/status,
you will get the current status (enabled/disabled) of binfmt_misc.
Change the status by echoing 0 (disables) or 1 (enables) or -1
(caution: this clears all previously registered binary
formats) to status. For example echo 0 > status to disable binfmt_misc
(temporarily). Each registered handler has an entry in /proc/sys/fs/binfmt_misc.
These files perform the same function as status, but their scope is limited
to the actual binary format. By 'cating' this file, you also receive
all related information about the interpreter/magic of the binfmt. An
example of the usage of binfmt_misc (emulate binfmt_java) follows:
cd /proc/sys/fs/binfmt_misc
echo ':Java:M::\xca\xfe\xba\xbe::/usr/local/java/bin/javawrapper:'
> register
echo ':HTML:E::html::/usr/local/java/bin/appletviewer:'
> register
echo ':Applet:M::<!--applet::/usr/local/java/bin/appletviewer:' >
register
echo ':DEXE:M::\x0eDEX::/usr/bin/dosexec:' < register
|
-
These four lines add support for Java executables and Java applets (like
binfmt_java, additionally recognizing the .html extension with no need to
put <!--applet> to every applet file). You have to install the JDK
and the shell-script /usr/local/java/bin/javawrapper too. It works around
the brokenness of the Java filename handling. To add a Java binary, just
create a link to the class-file somewhere in the path.
- /proc/sys/kernel
- This directory
reflects general kernel behaviors and the contents will be dependent upon
your configuration. Here you'll find the most important files, along
with descriptions of what they mean and how to use them.
- /proc/sys/kernel/acct
- The file
contains three values; highwater, lowwater, and frequency. It exists only
when BSD-style process accounting is enabled. These values control its
behavior. If the free space on the file system where the log lives goes
below lowwater percentage, accounting suspends. If it goes above highwater
percentage, accounting resumes. Frequency determines how often you check the
amount of free space (value is in seconds). Default settings are: 4, 2, and
30. That is, suspend accounting if there is less than 2 percent free; resume
it if we have a value of 3 or more percent; consider information about the
amount of free space valid for 30 seconds
- /proc/sys/kernel/ctrl-alt-del
-
When the value in this file is 0, ctrl-alt-del is trapped and sent to the
init program to handle a graceful restart. However, when the value is
greater that zero, Linux's reaction to this key combination will be an
immediate reboot, without syncing its dirty buffers. It should be noted that
when a program (like dosemu) has the keyboard in raw mode, the ctrl-alt-del
is intercepted by the program before it ever reaches the kernel tty layer,
and it is up to the program to decide what to do with it.
- /proc/sys/kernel/domainname, /proc/sys/kernel/hostname
-
These files can be controlled to set the NIS domainname and hostname of your
box. For the classic darkstar.frop.org a simple: # echo "darkstar"
> /proc/sys/kernel/hostname # echo "frop.org" >
/proc/sys/kernel/domainname would suffice to set your hostname and NIS
domainname. /proc/sys/kernel/osrelease, /proc/sys/kernel/ostype,
/proc/sys/kernel/version The names make it pretty obvious what these fields
contain: # cat /proc/sys/kernel/osrelease 2.2.12 # cat
/proc/sys/kernel/ostype Linux # cat /proc/sys/kernel/version #4 Fri Oct 1
12:41:14 PDT 1999 The files osrelease and ostype should be clear enough.
Version needs a little more clarification. The #4 means that this is the 4th
kernel built from this source base and the date after it indicates the time
the kernel was built. The only way to tune these values is to rebuild the
kernel.
- /proc/sys/kernel/panic
-
The value in this file represents the number of seconds the kernel waits
before rebooting on a panic. When you use the software watchdog, the
recommended setting is 60. If set to 0, the auto reboot after a kernel panic
is disabled, which is the default setting.
- /proc/sys/kernel/printk
- The four
values in printk denote * console_loglevel, * default_message_loglevel, *
minimum_console_level and * default_console_loglevel respectively. These
values influence printk() behavior when printing or logging error messages,
which come from inside the kernel. See syslog(2) for more information on the
different log levels.
- /proc/sys/kernel/console_loglevel
-
Messages with a higher priority than this will be printed to the console.
- /proc/sys/kernel/default_message_level
-
Messages without an explicit priority will be printed with this priority.
- /proc/sys/kernel/minimum_console_loglevel
-
Minimum (highest) value to which the console_loglevel can be set.
- /proc/sys/kernel/default_console_loglevel
-
Default value for console_loglevel.
- /proc/sys/kernel/sg-big-buff
- This
file shows the size of the generic SCSI (sg) buffer. At this point, you
can't tune it yet, but you can change it at compile time by editing
include/scsi/sg.h and changing the value of SG_BIG_BUFF. If you use a
scanner with SANE (Scanner Access Now Easy) you might want to set this to a
higher value. Refer to the SANE documentation on this issue.
- /proc/sys/kernel/modprobe
- The
location where the modprobe binary is located. The kernel uses this program
to load modules on demand.
- /proc/sys/vm
- The files in this
directory can be used to tune the operation of the virtual memory (VM)
subsystem of the Linux kernel. In addition, one of the files (bdflush) has
some influence on disk usage.
- nfract
-
This parameter governs the maximum number of dirty buffers in the buffer cache.
Dirty means that the contents of the buffer still have to be written to disk
(as opposed to a clean buffer, which can just be forgotten about). Setting
this to a higher value means that Linux can delay disk writes for a long
time, but it also means that it will have to do a lot of I/O at once when
memory becomes short. A lower value will spread out disk I/O more evenly.
- ndirty
-
Ndirty gives the maximum number of dirty buffers that bdflush can
write to the disk at one time. A high value will mean delayed, bursty I/O,
while a small value can lead to memory shortage when bdflush isn't woken
up often enough.
- nrefill
-
This is the number of buffers that bdflush will add
to the list of free buffers when refill_freelist() is called. It is
necessary to allocate free buffers beforehand, since the buffers are often
different sizes than the memory pages and some bookkeeping needs to be done
beforehand. The higher the number, the more memory will be wasted and the
less often refill_freelist() will need to run.
- nref_dirt
-
When refill_freelist() comes across more than nref_dirt dirty buffers, it will
wake up bdflush.
- age_buffer, age_super
-
Finally, the age_buffer and age_super parameters govern the maximum
time Linux waits before writing out a dirty buffer to disk.
The value is expressed in jiffies (clockticks), the number
of jiffies per second is 100. Age_buffer is the maximum age for data blocks,
while age_super is for filesystems meta data.
- buffermem
-
The three values in this file control how much memory should be
used for buffer memory. The percentage is calculated as a percentage
of total system memory.
- The values are:
- min_percent
-
This is the minimum percentage of memory that should be
spent on buffer memory.
- borrow_percent
-
When Linux is short on memory, and the buffer cache uses
more than it has been allotted, the memory management
(MM) subsystem will prune the buffer cache more heavily than other memory to
compensate.
- max_percent
-
This is the maximum amount of memory that can be
used for buffer memory.
- freepages
-
- This file contains three values: min, low and high:
- min
-
When the number of free pages in the system reaches this
number, only the kernel can allocate more memory.
- low
-
If the number of free pages falls below this point,
the kernel starts swapping aggressively.
- high
-
The kernel tries to keep up to this amount of memory free; if memory falls
below this point, the kernel starts gently swapping in the hopes that it
never has to do really aggressive swapping.
- kswapd
-
Kswapd is the kernel swap out daemon. That is, kswapd is that
piece of the kernel that frees memory when it gets fragmented
or full. Since every system is different, you'll
probably want some control over this piece of the system.
- The file contains three numbers:
- tries_base
-
The maximum number of pages kswapd tries to free
in one round is calculated from this number. Usually this number will be
divided by 4 or 8 (see mm/vmscan.c), so it isn't as big as it looks.
When you need to increase the bandwidth to/from swap, you'll want to
increase this number.
- tries_min
-
This is the minimum number of times kswapd
tries to free a page each time it is called. Basically it's just there
to make sure that kswapd frees some pages even when it's being called
with minimum priority.
- swap_cluster
-
This is probably the greatest influence
on system performance. swap_cluster is the number of pages kswapd writes in
one turn. You'll want this value to be large so that kswapd does its I/O
in large chunks and the disk doesn't have to seek as often, but you
don't want it to be too large since that would flood the request queue.
- overcommit_memory
-
This file contains one value. The following algorithm is
used to decide if there's enough memory: if the value of
overcommit_memory is positive, then there's always enough memory. This
is a useful feature, since programs often malloc() huge amounts of memory
'just in case', while they only use a small part of it. Leaving this
value at 0 will lead to the failure of such a huge malloc(), when in fact
the system has enough memory for the program to run. On the other hand,
enabling this feature can cause you to run out of memory and thrash the
system to death, so large and/or important servers will want to set this
value to 0.
- pagecache
-
This file does exactly the same job as buffermem, only
this file controls the amount of memory allowed for memory mapping and
generic caching of files. You don't want the minimum level to be too
low, otherwise your system might thrash when memory is tight or
fragmentation is high.
- pagetable_cache
-
The kernel keeps a number of page
tables in a per-processor cache (this helps a lot on SMP systems). The cache
size for each processor will be between the low and the high value. On a
low-memory, single CPU system, you can safely set these values to 0 so you
don't waste memory. It is used on SMP systems so that the system can
perform fast pagetable allocations without having to acquire the kernel
memory lock. For large systems, the settings are probably fine. For normal
systems they won't hurt a bit. For small systems ( less than 16MB ram)
it might be advantageous to set both values to 0.
- swapctl
-
- This file contains no less than 8 variables.
All of these values are used by kswapd. The first
four variables sc_max_page_age, sc_page_advance, sc_page_decline and
sc_page_initial_age are used to keep track of Linux's page aging. Page
ageing is a bookkeeping method to track which pages of memory are often
used, and which pages can be swapped out without consequences.
- When a page is swapped in, it starts at sc_page_initial_age (default 3)
and when the page is scanned by kswapd, its age is adjusted
according to the following scheme.
- If the page was used since the last time we scanned, its age is
increased by sc_page_advance (default 3). Where the maximum value is given
by sc_max_page_age (default 20). Otherwise (meaning it wasn't used)
its age is decreased by sc_page_decline (default 1).
- When a page reaches age 0, it's ready to be swapped out.
- The variables sc_age_cluster_fract,
sc_age_cluster_min, sc_pageout_weight and sc_bufferout_weight, can be used
to control kswapd's aggressiveness in swapping out pages.
- Sc_age_cluster_fract is used to calculate how many pages from a process are
to be scanned by kswapd. The formula used is
- (sc_age_cluster_fract divided by 1024) times resident set size
- So if you want kswapd to scan the whole process,
sc_age_cluster_fract needs to have a value of 1024. The minimum
number of pages kswapd will scan is represented by sc_age_cluster_min, which
is done so that kswapd will also scan small processes. The values of
sc_pageout_weight and sc_bufferout_weight are used to control how many tries
kswapd will make in order to swap out one page/buffer. These values can be
used to fine-tune the ratio between user pages and buffer/cache memory. When
you find that your Linux system is swapping out too many process pages in
order to satisfy buffer memory demands, you may want to either increase
sc_bufferout_weight, or decrease the value of sc_pageout_weight.
- /proc/sys/dev
- Device specific
parameters. Currently there is only support for CDROM drives, and for those,
there is only one read-only file containing information about the CD-ROM
drives attached to the system: >cat /proc/sys/dev/cdrom/info CD-ROM
information, Id: cdrom.c 2.55 1999/04/25 drive name: sr0 hdb drive speed: 32
40 drive # of slots: 1 0 Can close tray: 1 1 Can open tray: 1 1 Can lock
tray: 1 1 Can change speed: 1 1 Can select disk: 0 1 Can read multisession:
1 1 Can read MCN: 1 1 Reports media changed: 1 1 Can play audio: 1 1 You see
two drives, sr0 and hdb, along with a list of their features.
- SUNRPC
-
- /proc/sys/sunrpc
-
This directory contains four files, which enable or disable debugging for
the RPC functions NFS, NFS-daemon, RPC and NLM. The default values are 0.
They can be set to one to turn debugging on. (The default value is 0 for
each)
- /proc/sys/net
-
The interface to the networking parts of the kernel is located in
/proc/sys/net. The following table shows all possible subdirectories. You
may see only some of them, depending on your kernel's configuration. Our
main focus will be on IP networking since AX15, X.25, and DEC Net are only
minor players in the Linux world. Should you wish review the online
documentation and the kernel source to get a detailed view of the parameters
for those protocols not covered here. In this section we'll discuss the
subdirectories listed above. As default values are suitable for most needs,
there is no need to change these values.
- GENERAL PARAMETERS
-
- /proc/sys/net/core
-
Network core options
- rmem_default
- The default setting
of the socket receive buffer in bytes.
- rmem_max
- The maximum receive
socket buffer size in bytes.
- wmem_default
- The default setting
(in bytes) of the socket send buffer.
- wmem_max
- The maximum send socket
buffer size in bytes.
- message_burst and message_cost
-
These parameters are used to limit the warning messages written to the
kernel log from the networking code. They enforce a rate limit to make a
denial-of-service attack impossible. A higher message_cost factor, results
in fewer messages that will be written. Message_burst controls when messages
will be dropped. The default settings limit warning messages to one every
five seconds.
- netdev_max_backlog
-
Maximum number of packets, queued on the INPUT side, when the interface
receives packets faster than kernel can process them.
- optmem_max
- Maximum ancillary
buffer size allowed per socket. Ancillary data is a sequence of struct
cmsghdr structures with appended data.
- UNIX DOMAIN SOCKETS
-
- /proc/sys/net/unix
-
Parameters for Unix domain sockets
- There are only two files in this subdirectory. They control the
delays for deleting and destroying socket descriptors.
- IPv4
-
- /proc/sys/net/ipv4
- IPV4 settings.
IP version 4 is still the most used protocol in Unix networking. It will be
replaced by IP version 6 in the next couple of years, but for the moment
it's the de facto standard for the internet and is used in most
networking environments around the world. Because of the importance of this
protocol, we'll have a deeper look into the subtree controlling the
behavior of the Ipv4 subsystem of the Linux kernel.
- Let's start with the entries in /proc/sys/net/ipv4.
- ICMP settings
-
- icmp_echo_ignore_all and icmp_echo_ignore_broadcasts
- Turn on (1) or off (0), if the kernel should ignore all ICMP ECHO requests, or just those to
broadcast and multicast addresses.
- Please note that if you accept ICMP echo requests with a
broadcast/multi\-cast destination address your network
may be used as an exploder for denial of service packet flooding attacks to
other hosts.
- icmp_destunreach_rate, icmp_echoreply_rate, icmp_paramprob_rate
and icmp_timeexeed_rate
-
Sets limits for sending ICMP packets to specific
targets. A value of zero disables all limiting. Any positive value sets
the maximum package rate in hundredth of a second (on
Intel systems).
- IP settings
-
- ip_autoconfig
- This file contains
the number one if the host received its IP configuration by RARP, BOOTP,
DHCP or a similar mechanism. Otherwise it is zero.
- ip_default_ttl
- TTL (Time To Live)
for IPv4 interfaces. This is simply the maximum number of hops a packet may
travel.
- ip_dynaddr
-
Enable dynamic socket address rewriting on interface address change. This is
useful for dialup interface with changing IP addresses.
- ip_forward
- Enable or disable
forwarding of IP packages between interfaces. Changing this value resets all
other parameters to their default values. They differ if the kernel is
configured as host or router.
- ip_local_port_range
- Range of
ports used by TCP and UDP to choose the local port. Contains two numbers,
the first number is the lowest port, the second number the highest local
port. Default is 1024-4999. Should be changed to 32768-61000 for high-usage
systems.
- ip_no_pmtu_disc
-
Global switch to turn path MTU discovery off. It can also be set on a per
socket basis by the applications or on a per route basis.
- ip_masq_debug
- Enable/disable
debugging of IP masquerading.
- IP fragmentation settings
-
- ipfrag_high_trash and ipfrag_low_trash
- Maximum
memory used to reassemble IP fragments. When ipfrag_high_thrash bytes
of memory is allocated for this purpose, the fragment handler will toss
packets until ipfrag_low_thrash is reached.
- ipfrag_time
-
Time in seconds to keep an IP fragment in memory.
- TCP settings
-
- tcp_ecn
-
This file controls the use of the ECN bit in the IPv4 headers, this is a new
feature about Explicit Congestion Notification, but some routers and
firewalls block traffic that has this bit set, so it could be necessary to
echo 0 to /proc/sys/net/ipv4/tcp_ecn, if you want to talk to this sites. For
more info you could read RFC2481.
- tcp_retrans_collapse
- Bug-to-bug
compatibility with some broken printers. On retransmit, try to send larger
packets to work around bugs in certain TCP stacks. Can be turned off by
setting it to zero.
- tcp_keepalive_probes
- Number of
keep alive probes TCP sends out, until it decides that the connection is
broken.
- tcp_keepalive_time
-
How often TCP sends out keep alive messages, when keep alive is enabled. The
default is 2 hours.
- tcp_syn_retries
- Number of times
initial SYNs for a TCP connection attempt will be retransmitted. Should not
be higher than 255. This is only the timeout for outgoing connections, for
incoming connections the number of retransmits is defined by tcp_retries1.
- tcp_sack
- Enable select
acknowledgments after RFC2018.
- tcp_timestamps
- Enable timestamps
as defined in RFC1323.
- tcp_stdurg
- Enable the strict
RFC793 interpretation of the TCP urgent pointer field. The default is to use
the BSD compatible interpretation of the urgent pointer pointing to the
first byte after the urgent data. The RFC793 interpretation is to have it
point to the last byte of urgent data. Enabling this option may lead to
interoperability problems. Disabled by default.
- tcp_syncookies
- Only valid when
the kernel was compiled with CONFIG_SYNCOOKIES. Send out syncookies when the
syn backlog queue of a socket overflows. This is to ward off the common
'syn flood attack'. Disabled by default. Note that the concept of a
socket backlog is abandoned. This means the peer may not receive reliable
error messages from an over loaded server with syncookies enabled.
- tcp_window_scaling
- Enable window
scaling as defined in RFC1323.
- tcp_fin_timeout
- The length of
time in seconds it takes to receive a final FIN before the socket is always
closed. This is strictly a violation of the TCP specification, but required
to prevent denial-of-service attacks.
- tcp_max_ka_probes
- Indicates how
many keep alive probes are sent per slow timer run. Should not be set too
high to prevent bursts.
- tcp_max_syn_backlog
- Length of the
per socket backlog queue. Since Linux 2.2 the backlog specified in listen(2)
only specifies the length of the backlog queue of already established
sockets. When more connection requests arrive Linux starts to drop packets.
When syncookies are enabled the packets are still answered and the maximum
queue is effectively ignored.
- tcp_retries1
- Defines how often an
answer to a TCP connection request is retransmitted before giving up.
- tcp_retries2
- Defines how often a
TCP packet is retransmitted before giving up.
- /proc/sys/net/ipv4/conf
-
- Here you'll find one subdirectory for each interface the system knows
about and one directory called all. Changes in the all subdirectory affect all
interfaces, whereas changes in the other subdirectories affect only one
interface. All directories have the same entries:
- accept_redirects
- This switch
decides if the kernel accepts ICMP redirect messages or not. The default is
'yes' if the kernel is configured for a regular host and
'no' for a router configuration.
- accept_source_route
- Should source
routed packages be accepted or declined. The default is dependent on the
kernel configuration. It's 'yes' for routers and 'no'
for hosts.
- bootp_relay
-
Accept packets with source address 0.b.c.d with destinations not to this
host as local ones. It is supposed that a BOOTP relay daemon will catch and
forward such packets. The default is 0.
- forwarding
- Enable or disable IP
forwarding on this interface.
- log_martians
- Log packets with
source addresses with no known route to kernel log.
- mc_forwarding
- Do multicast
routing. The kernel needs to be compiled with CONFIG_MROUTE and a multicast
routing daemon is required.
- proxy_arp
- Does (1) or does not
(0) perform proxy ARP.
- rp_filter
- Integer value
determines if a source validation should be made. 1 means yes, 0 means no.
Disabled by default, but local/broadcast address spoofing is always on. If
you set this to 1 on a router that is the only connection for a network to
the net, it will prevent spoofing attacks against your internal networks
(external addresses can still be spoofed), without the need for additional
firewall rules.
- secure_redirects
- Accept ICMP
redirect messages only for gateways, listed in default gateway list. Enabled
by default.
- shared_media
-
If it is not set the kernel does not assume that different subnets on this
device can communicate directly. Default setting is 'yes'.
- send_redirects
- Determines whether
to send ICMP redirects to other hosts.
- Routing settings
- The directory
/proc/sys/net/ipv4/route contains several file to control routing issues.
- error_burst and error_cost
- These
parameters are used to limit the warning messages written to the kernel log
from the routing code. The higher the error_cost factor is, the fewer
messages will be written. Error_burst controls when messages will be
dropped. The default settings limit warning messages to one every five
seconds.
- flush
-
Writing to this file results in a flush of the routing cache.
- gc_elastic, gc_interval, gc_min_interval, gc_tresh,
gc_timeout
- Values to control the frequency and
behavior of the garbage collection algorithm for the routing cache.
- max_size
- Maximum size of the
routing cache. Old entries will be purged once the cache reached has this
size.
- max_delay,
min_delay
- Delays for flushing the routing cache.
- redirect_load, redirect_number
-
Factors which determine if more ICPM redirects should be sent to a specific
host. No redirects will be sent once the load limit or the maximum number of
redirects has been reached.
- redirect_silence
- Timeout for
redirects. After this period redirects will be sent again, even if this has
been stopped, because the load or number limit has been reached.
- /proc/sys/net/ipv4/neigh
- Network
Neighbor handling. It contains settings about how to handle connections with
direct neighbors (nodes attached to the same link). As we saw it in the conf
directory, there is a default subdirectory which holds the default values,
and one directory for each interface. The contents of the directories are
identical, with the single exception that the default settings contain
additional options to set garbage collection parameters.
- In the interface directories you'll find the following entries:
- base_reachable_time
- A base value
used for computing the random reachable time value as specified in RFC2461.
- retrans_time
- The time, expressed
in jiffies (1/100 sec), between retransmitted Neighbor Solicitation
messages. Used for address resolution and to determine if a neighbor is
unreachable.
- unres_qlen
-
Maximum queue length for a pending arp request - the number of packets which
are accepted from other layers while the ARP address is still resolved.
- anycast_delay
- Maximum for random
delay of answers to neighbor solicitation messages in jiffies (1/100 sec).
Not yet implemented (Linux does not have anycast support yet).
- ucast_solicit
- Maximum number of
retries for unicast solicitation.
- mcast_solicit
- Maximum number of
retries for multicast solicitation.
- delay_first_probe_time
- Delay for
the first time probe if the neighbor is reachable. (see gc_stale_time)
- locktime
- An ARP/neighbor entry is
only replaced with a new one if the old is at least locktime old. This
prevents ARP cache thrashing.
- proxy_delay
- Maximum time (real
time is random [0..proxytime]) before answering to an ARP request for which
we have an proxy ARP entry. In some cases, this is used to prevent network
flooding.
- proxy_qlen
-
Maximum queue length of the delayed proxy arp timer. (see proxy_delay).
- app_solcit
- Determines the number
of requests to send to the user level ARP daemon. Use 0 to turn off.
- gc_stale_time
- Determines how
often to check for stale ARP entries. After an ARP entry is stale it will be
resolved again (which is useful when an IP address migrates to another
machine). When ucast_solicit is greater than 0 it first tries to send an ARP
packet directly to the known host When that fails and mcast_solicit is
greater than 0, an ARP request is broadcasted.
- APPLETALK
-
- /proc/sys/net/appletalk
-
Holds the Appletalk configuration data when Appletalk is loaded. The
configurable parameters are:
- aarp-expiry-time
-
The amount of time we keep an ARP entry before expiring it. Used to age out
old hosts.
- aarp-resolve-time
-
The amount of time we will spend trying to resolve an Appletalk address.
- aarp-retransmit-limit
-
The number of times we will retransmit a query before giving up.
- aarp-tick-time
-
Controls the rate at which expires are checked.
- /proc/net/appletalk
- Holds the
list of active Appletalk sockets on a machine. The fields indicate the DDP
type, the local address (in network:node format) the remote address, the
size of the transmit pending queue, the size of the received queue (bytes
waiting for applications to read) the state and the uid owning the socket.
- /proc/net/atalk_iface
- lists all
the interfaces configured for appletalk. It shows the name of the interface,
its Appletalk address, the network range on that address (or network number
for phase 1 networks), and the status of the interface.
- /proc/net/atalk_route
- lists each
known network route. It lists the target (network) that the route leads to,
the router (may be directly connected), the route flags, and the device the
route is using.
- IPX
-
- The IPX protocol has no tunable values in proc/sys/net, it does,
however, provide proc/net/ipx. This lists each IPX socket giving the local
and remote addresses in Novell format (that is network:node:port). In
accordance with the strange Novell tradition, everything but the port is in
hex. Not_Connected is displayed for sockets that are not tied to a specific
remote address. The Tx and Rx queue sizes indicate the number of bytes
pending for transmission and reception. The state indicates the state the
socket is in and the uid is the owning uid of the socket.
- ipx_interface
- Lists all IPX interfaces. For each interface it gives the network number, the node number, and indicates if the network is the
primary network. It also indicates which device it is bound to (or Internal
for internal networks) and the Frame Type if appropriate. Linux supports
802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for IPX.
- ipx_route
- Table holding a list of IPX routes. For each route it gives
the destination network, the router node (or Directly) and the network
address of the router (or Connected) for internal networks.
- /proc/sysvipc
- Info of SysVIPC
Resources (msg, sem, shm) (2.4)
- /proc/tty
- Information about the
available and actually used tty's can be found in the directory
/proc/tty. You'll find entries for drivers and line disciplines in this
directory.
- /proc/tty/drivers
-
list of drivers and their usage.
- /proc/tty/ldiscs
- registered line
disciplines.
- /proc/tty/driver/serial
-
usage statistic and status of single tty lines.
- To see which tty's are currently in use, you can simply
look into the file /proc/tty/drivers:
-
# cat /proc/tty/drivers
serial /dev/cua 5 64-127 serial:callout
serial /dev/ttyS 4 64-127 serial
pty_slave /dev/pts 143 0-255 pty:slave
pty_master /dev/ptm 135 0-255 pty:master
pty_slave /dev/pts 142 0-255 pty:slave
pty_master /dev/ptm 134 0-255 pty:master
pty_slave /dev/pts 141 0-255 pty:slave
pty_master /dev/ptm 133 0-255 pty:master
pty_slave /dev/pts 140 0-255 pty:slave
pty_master /dev/ptm 132 0-255 pty:master
pty_slave /dev/pts 139 0-255 pty:slave
pty_master /dev/ptm 131 0-255 pty:master
pty_slave /dev/pts 138 0-255 pty:slave
pty_master /dev/ptm 130 0-255 pty:master
pty_slave /dev/pts 137 0-255 pty:slave
pty_master /dev/ptm 129 0-255 pty:master
pty_slave /dev/pts 136 0-255 pty:slave
pty_master /dev/ptm 128 0-255 pty:master
pty_slave /dev/ttyp 3 0-255 pty:slave
pty_master /dev/pty 2 0-255 pty:master
/dev/vc/0 /dev/vc/0 4 0 system:vtmaster
/dev/ptmx /dev/ptmx 5 2 system
/dev/console /dev/console 5 1 system:console
/dev/tty /dev/tty 5 0 system:/dev/tty
unknown /dev/vc/%d 4 1-63 console
|
- Note that while the above files tend to be
easily readable text files, they can sometimes be formatted in a way that is
not easily digestible. There are many commands that do little more than read
the above files and format them for easier understanding. For example, the
free program reads /proc/meminfo and converts the amounts given in bytes to
kilobytes (and adds a little more information, as well).
- /proc/uptime
- The time the system
has been up.
- /proc/version
-
The kernel version.
- /proc/video
- BTTV info of video
resources.
1.15. /root
This is the home directory of the System Administrator, 'root'.
This may be somewhat confusing ('root on root') but in former days,
'/' was root's home directory (hence the name of the Administrator
account). To keep things tidier, 'root' got his own home directory.
Why not in '/home'? Because '/home' is often located on a different
partition or even on another system and would thus be inaccessible
to 'root' when - for some reason - only '/' is mounted.
The FSSTND merely states that this is the recommended location for
the home directory of 'root'. It is left up to the end user to determine
the home directory of 'root'. However, the FSSTND also says that:
If the home directory of the root account is not stored on the root
partition it will be necessary to make certain it will default to
/ if it can not be located.
We recommend against using the root account for tasks that can be
performed as an unprivileged user, and that it be used solely for
system administration. For this reason, we recommend that subdirectories
for mail and other applications not appear in the root account's home
directory, and that mail for administration roles such as root, postmaster,
and webmaster be forwarded to an appropriate user.
|
1.16. /sbin
Linux discriminates between 'normal' executables and those used for
system maintenance and/or administrative tasks. The latter reside either here
or - the less important ones - in /usr/sbin. Locally installed system
administration programs should be placed into /usr/local/sbin.
Programs executed after /usr is known to be mounted (when there are no problems)
are generally placed into /usr/sbin. This directory contains binaries
that are essential to the working of the system. These include system
administration as well as maintenance and hardware configuration programs.
You may find lilo, fdisk, init, ifconfig, etc.... here.
Another directory that contains system binaries is /usr/sbin. This
directory contains other binaries of use to the system administrator.
This is where you will find the network daemons for your system along
with other binaries that (generally) only the system administrator has access to,
but which are not required for system maintenance and repair. Normally,
these directories are never part of normal user's $PATHs, only of roots
(PATH is an environment variable that controls the sequence of locations
that the system will attempt to look in for commands).
The FSSTND states that:
/sbin should contain only binaries essential for booting, restoring,
recovering, and/or repairing the system in addition to the binaries
in /bin.
|
A particular eccentricity of the Linux filesystem hierarchy
is that originally /sbin binaries were kept in /etc.
Deciding what things go into "sbin" directories is simple: if a normal
(not a system administrator) user will ever run it directly, then it
must be placed in one of the "bin" directories. Ordinary users should
not have to place any of the sbin directories in their path.
For example, files such as chfn which users only occasionally use must
still be placed in /usr/bin. ping, although it is absolutely necessary
for root (network recovery and diagnosis) is often used by users and
must live in /bin for that reason.
We recommend that users have read and execute permission for everything
in /sbin except, perhaps, certain setuid and setgid programs. The
division between /bin and /sbin was not created for security reasons or
to prevent users from seeing the operating system, but to provide a
good partition between binaries that everyone uses and ones that are
primarily used for administration tasks. There is no inherent security
advantage in making /sbin off-limits for users.
|
FSSTND compliance requires that the following commands, or symbolic links to commands,
are required in /sbin.
shutdown Command to bring the system down.
|
The following files, or symbolic links to files, must be in /sbin
if the corresponding subsystem is installed:
fastboot Reboot the system without checking the disks (optional)
fasthalt Stop the system without checking the disks (optional)
fdisk Partition table manipulator (optional)
fsck File system check and repair utility (optional)
fsck.* File system check and repair utility for a specific filesystem (optional)
getty The getty program (optional)
halt Command to stop the system (optional)
ifconfig Configure a network interface (optional)
init Initial process (optional)
mkfs Command to build a filesystem (optional)
mkfs.* Command to build a specific filesystem (optional)
mkswap Command to set up a swap area (optional)
reboot Command to reboot the system (optional)
route IP routing table utility (optional)
swapon Enable paging and swapping (optional)
swapoff Disable paging and swapping (optional)
update Daemon to periodically flush filesystem buffers (optional)
|
1.17. /usr
/usr usually contains by far the largest share of data on a system. Hence,
this is one of the most important directories in the system as it contains
all the user binaries, their documentation, libraries, header files, etc....
X and its supporting libraries can be found here. User programs like telnet,
ftp, etc.... are also placed here. In the original Unix implementations, /usr
was where the home directories of the users were placed (that is to say,
/usr/someone was then the directory now known as /home/someone). In current
Unices, /usr is where user-land programs and data (as opposed to 'system land'
programs and data) are. The name hasn't changed, but it's meaning has narrowed
and lengthened from "everything user related" to "user usable programs and data".
As such, some people may now refer to this directory as meaning 'User System Resources'
and not 'user' as was originally intended.
/usr is shareable, read-only data. That means that /usr should
be shareable between various FHS-compliant hosts and must not be written to.
Any information that is host-specific or varies with time is stored elsewhere.
Large software packages must not use a direct subdirectory under the /usr
hierarchy.
|
- /usr/X11R6
-
-
Another large
subdirectory structure begins here, containing libraries, executables,
docs, fonts and much more concerning the X Window System. Its inclusion
here is somewhat inconsistent and so is the difference between '/usr'
and '/usr/X11R6' directories. One would assume that programs that run on
X only have their files in the '/usr/X11R6' hierarchy, while the others
use '/usr'. Regrettably, it isn't so. KDE and GNOME put their files in
the '/usr' hierarchy, whereas the window manager Window Maker uses
'/usr/X11R6'. Documentation files for X11R6 are not in '/usr/X11R6/doc',
but primarily in '/usr/X11R6/lib/X11/doc'. This mess is due to the fact
that in contrast to other operating systems, the graphical desktop
isn't an integral part of the system. Linux is still primarily used on
servers, where graphical systems don't make sense.
-
This hierarchy is reserved for the X Window System, version 11 release
6, and related files. To simplify matters and make XFree86 more
compatible with the X Window System on other systems, the following
symbolic links must be present if /usr/X11R6 exists:
/usr/bin/X11 -> /usr/X11R6/bin
/usr/lib/X11 -> /usr/X11R6/lib/X11
/usr/include/X11 -> /usr/X11R6/include/X11
|
-
In
general, software must not be installed or managed via the above
symbolic links. They are intended for utilization by users only. The
difficulty is related to the release version of the X Window System - in
transitional periods, it is impossible to know what release of X11 is
in use.
- /usr/X11R6/bin
-
XFree86 system binaries.
These are necessary for the initialisation, configuration and running of
the X windowing system. X, xf86config, xauth, xmodmap and even xpenguin
are located here.
- /usr/X11R6/include
-
XFree86 system header files. There are required for the compilation of some applications that utilise the X toolkit.
- /usr/X11R6/lib
-
XFree86 system libraries.
- /usr/X11R6/lib/modules
-
XFree86 system modules. These are the modules that X loads upon startup.
Without these modules video4linux, DRI and GLX extensions and drivers
for certain input devices would cease to function.
- /usr/X11R6/lib/X11/fonts
-
XFree86 system fonts. Fonts that are utilised by 'xfs' (the X Font Server) and programs of that ilk.
- /usr/bin
-
This directory contains the vast majority of binaries on your system.
Executables in this directory vary widely. For instance vi, gcc,
gnome-session and mozilla and are all found here.
- /usr/doc
-
The central documentation directory. Documentation is actually located in /usr/share/doc and linked from here.
- /usr/etc
-
Theoretically, that's another directory for configuration files. Virtually unused now.
- /usr/games
-
Once upon a time, this directory contained network games files. Rarely used now.
- /usr/include
-
The directory for 'header files', needed for compiling user space source code.
- /usr/include/'package-name'
-
Application specific header files.
- /usr/info
-
This directory used to contain the files for the info documentation system. Now they are in '/usr/share/info'.
- /usr/lib
-
This directory contains program libraries. Libraries are collections of frequently used program routines.
- /usr/local
-
The original idea behind '/usr/local' was to have a separate ('local')
'/usr' directory on every machine besides '/usr', which might be just
mounted read-only from somewhere else. It copies the structure of
'/usr'. These days, '/usr/local' is widely regarded as a good place in
which to keep self-compiled or third-party programs.
The /usr/local hierarchy is for use by the system administrator when
installing software locally. It needs to be safe from being overwritten
when the system software is updated. It may be used for programs and
data that are shareable amongst a group of hosts, but not found in /usr.
Locally installed software must be placed within /usr/local rather than
/usr unless it is being installed to replace or upgrade software in
/usr.
- /usr/man
-
It once held the man pages. It has been moved to /usr/share/man.
- /usr/sbin
-
This directory contains programs for administering a system, meant to be
run by 'root'. Like '/sbin', it's not part of a user's $PATH. Examples
of included binaries here are chroot, useradd, in.tftpd and pppconfig.
- /usr/share
-
This directory contains 'shareable', architecture-independent files
(docs, icons, fonts etc). Note, however, that '/usr/share' is generally
not intended to be shared by different operating systems or by different
releases of the same operating system. Any program or package which
contains or requires data that doesn't need to be modified should store
that data in '/usr/share' (or '/usr/local/share', if installed locally).
It is recommended that a subdirectory be used in /usr/share for this
purpose."
- /usr/share/doc
-
Location of package
specific documentation files. These directories often contain useful
information that might not be in the man pages. They may also contain
templates and configuration files for certain utilities making
configuration that much easier.
- /usr/share/info
-
Location of 'info' pages. This style of documentation seems to be largely ignored now. Manual pages are in far greater favour.
- /usr/share/man
-
Manual pages. They are organised into 8 sections, which are explained below.
-
man1: User programs
Manual pages that describe publicly accessible commands are contained
in this chapter. Most program documentation that a user will need to
use is located here.
man2: System calls
This section describes all of the system calls (requests for the kernel
to perform operations).
man3: Library functions and subroutines
Section 3 describes program library routines that are not direct calls
to kernel services. This and chapter 2 are only really of interest to
programmers.
man4: Special files
Section 4 describes the special files, related driver functions, and
networking support available in the system. Typically, this includes
the device files found in /dev and the kernel interface to networking
protocol support.
man5: File formats
The formats for many data files are documented in the section 5. This
includes various include files, program output files, and system files.
man6: Games
This chapter documents games, demos, and generally trivial programs.
Different people have various notions about how essential this is.
man7: Miscellaneous Manual pages that are difficult to classify are
designated as being section 7. The troff and other text processing
macro packages are found here.
man8: System administration Programs used by system administrators
for system operation and maintenance are documented here. Some of
these programs are also occasionally useful for normal users.
|
- /usr/src
-
The 'linux' sub-directory holds the Linux kernel sources, header-files and documentation.
- /usr/src/RPM
-
RPM provides a substructure for building RPMs from SRPMs. Organisation
of this branch is fairly logical with packages being organised according
to a package's architecture.
- /usr/src/RPM/BUILD
-
A temporary store for RPM binary files that are being built from source code.
- /usr/src/RPM/RPMS/athlon,
/usr/src/RPM/RPMS/i386, /usr/src/RPM/RPMS/i486, /usr/src/RPM/RPMS/i586,
/usr/src/RPM/RPMS/i686, /usr/src/RPM/RPMS/noarch
-
These directories contain architecture dependant RPM source files.
- /usr/src/RPM/SOURCES
-
This directory contains the source TAR files, patches, and icon files for software to be packaged.
- /usr/src/RPM/SPECS
-
RPM SPEC files. A SPEC file is a file that contains information as well as scripts that are necessary to build a package.
- /usr/src/RPM/SRPMS
-
Contains the source RPM files which result from a build.
- /usr/src/linux
-
Contains the source code for the Linux kernel.
- /usr/src/linux/.config
-
The last kernel source configuration. This file is normally created
through the 'make config', 'make menuconfig' or 'make xconfig' steps
during kernel compilation.
- /usr/src/linux/.depend, /usr/src/linux/.hdepend
-
'make dep' checks the dependencies of the selections you made when you
created your .config file. It ensures that the required files can be
found and it builds a list that is to be used during compilation. Should
this process be successful these two files are created.
- /usr/src/linux/COPYING
-
GNU License
- /usr/src/linux/CREDITS
-
A partial credits-file of people that have contributed to the Linux
project. It is sorted by name and formatted to allow easy grepping and
beautification by scripts. The fields are: name (N), email (E),
web-address (W), PGP key ID and fingerprint (P), description (D), and
snail-mail address (S).
- /usr/src/linux/MAINTAINERS
-
List of maintainers and details on how to submit kernel changes.
- /usr/src/linux/Makefile
-
Contains data necessary for compilation of a working kernel. It allows
developers and end-users to compile a kernel with a few simple steps
(ie. make dep, make clean, make bzImage, make modules, make
modules_install) and also not have to worry about re-compiling
everything from scratch if parts of it have already been done so and are
up to date.
- /usr/src/linux/README
-
These are the
release notes for Linux version 2.4. Read them carefully, as they tell
you what this is all about, explain how to install the kernel, and what
to do if something goes wrong.
- /usr/src/linux/REPORTING-BUGS
-
A suggested procedure for reporting Linux bugs. You aren't obliged to
use the bug reporting format, it is provided as a guide to the kind of
information that can be useful to developers - no more.
- /usr/src/linux/Rules.make
-
This file contains rules which are shared between multiple Makefiles.
- /usr/src/linux/Documentation
-
Contains documentation that may be necessary in order to re-compile a
kernel. However, it also provides quite a lot of information about your
Linux system in general as well. For those who wish to seek further
information on the contents of this directory you may consult the
/usr/src/linux/Documentation/00-INDEX file. Further, more detailed
documentation may be found in /usr/src/linux/Documentation/Docbook. Of
course, the contents of this directory is written in Docbook but may be
converted to pdf, ps or html using the make targets of 'pdfdocs',
'psdocs' and 'htmldocs' respectively.
- /usr/tmp
-
User space temporary files. This directory is not found on modern
distributions at all and was most likely created as a consequence of
Linux's UNIX heritage.
1.18. /var
Contains variable data like system logging files, mail and printer
spool directories, and transient and temporary files.
Some portions of /var are not shareable between different systems. For
instance, /var/log, /var/lock, and /var/run. Other portions may be shared,
notably /var/mail, /var/cache/man, /var/cache/fonts, and /var/spool/news.
Why not put it into /usr? Because there might
be circumstances when you may want to mount /usr as read-only, e.g. if it is
on a CD or on another computer. '/var' contains variable data, i.e.
files and directories the system must be able to write to during operation,
whereas /usr should only contain static data. Some directories can
be put onto separate partitions or systems, e.g. for easier backups, due to
network topology or security concerns. Other directories have to be on the
root partition, because they are vital for the boot process.
'Mountable' directories are: '/home', '/mnt',
'/tmp', '/usr' and '/var'. Essential for booting
are: '/bin', '/boot', '/dev', '/etc',
'/lib', '/proc' and '/sbin'.
If /var cannot be made a separate partition, it is often preferable to move /
var out of the root partition and into the /usr partition. (This is sometimes
done to reduce the size of the root partition or when space runs low in the
root partition.) However, /var must not be linked to /usr because this makes
separation of /usr and /var more difficult and is likely to create a naming
conflict. Instead, link /var to /usr/var.
Applications must generally not add directories to the top level of /var. Such
directories should only be added if they have some system-wide implication, and
in consultation with the FHS mailing list.
|
- /var/backups
- Directory
containing backups of various key system files such as /etc/shadow,
/etc/group, /etc/inetd.conf and dpkg.status. They are normally renamed to
something like dpkg.status.0, group.bak, gshadow.bak, inetd.conf.bak,
passwd.bak, shadow.bak
- /var/cache
- Is
intended for cached data from applications. Such data is locally generated
as a result of time-consuming I/O or calculation. This data can generally be
regenerated or be restored. Unlike /var/spool, files here can be deleted
without data loss. This data remains valid between invocations of the
application and rebooting of the system. The existence of a separate
directory for cached data allows system administrators to set different disk
and backup policies from other directories in /var.
- /var/cache/fonts
- Locally-generated
fonts. In particular, all of the fonts which are automatically generated by
mktexpk must be located in appropriately-named subdirectories of /var/cache/
fonts.
- /var/cache/man
- A
cache for man pages that are formatted on demand. The source for manual
pages is usually stored in /usr/share/man/; some manual pages might come
with a pre-formatted version, which is stored in /usr/share/man/cat* (this
is fairly rare now). Other manual pages need to be formatted when they are
first viewed; the formatted version is then stored in /var/man so that the
next person to view the same page won't have to wait for it to be
formatted (/var/catman is often cleaned in the same way temporary
directories are cleaned).
- /var/cache/'package-name'
- Package
specific cache data.
- /var/cache/www
- WWW
proxy or cache data.
- /var/crash
- This
directory will eventually hold system crash dumps. Currently, system crash
dumps are not supported under Linux. However, development is already
complete and is awaiting unification into the Linux kernel.
- /var/db
- Data
bank store.
- /var/games
- Any
variable data relating to games in /usr is placed here. It holds variable
data that was previously found in /usr. Static data, such as help text,
level descriptions, and so on, remains elsewhere though, such as in
/usr/share/games. The separation of /var/games and /var/lib as in release
FSSTND 1.2 allows local control of backup strategies, permissions, and disk
usage, as well as allowing inter-host sharing and reducing clutter in
/var/lib. Additionally, /var/games is the path traditionally used by BSD.
- /var/lib
- Holds
dynamic data libraries/files like the rpm/dpkg database and game scores.
Furthermore, this hierarchy holds state information pertaining to an
application or the system. State information is data that programs modify
while they run, and that pertains to one specific host. Users shouldn't
ever need to modify files in /var/lib to configure a package's
operation. State information is generally used to preserve the condition of
an application (or a group of inter-related applications) between
invocations and between different instances of the same application. An
application (or a group of inter-related applications) use a subdirectory of
/var/lib for their data. There is one subdirectory, /var/lib/misc, which is
intended for state files that don't need a subdirectory; the other
subdirectories should only be present if the application in question is
included in the distribution. /var/lib/'name' is the location that
must be used for all distribution packaging support. Different distributions
may use different names, of course.
- /var/local
- Variable
data for local programs (i.e., programs that have been installed by the
system administrator) that are installed in /usr/local (as opposed to a
remotely mounted '/var' partition). Note that even locally installed
programs should use the other /var directories if they are appropriate,
e.g., /var/lock.
- /var/lock
- Many
programs follow a convention to create a lock file in /var/lock to indicate
that they are using a particular device or file. This directory holds those
lock files (for some devices) and hopefully other programs will notice the
lock file and won't attempt to use the device or file.
Lock
files should be stored within the /var/lock directory structure. Lock files
for devices and other resources shared by multiple applications, such as the
serial device lock files that were originally found in either
/usr/spool/locks or /usr/spool/uucp, must now be stored in /var/lock. The
naming convention which must be used is LCK.. followed by the base name of
the device file. For example, to lock /dev/ttyS0 the file LCK..ttyS0 would
be created. The format used for the contents of such lock files must be the
HDB UUCP lock file format. The HDB format is to store the process identifier
(PID) as a ten byte ASCII decimal number, with a trailing newline. For
example, if process 1230 holds a lock file, it would contain the eleven
characters: space, space, space, space, space, space, one, two, three, zero,
and newline.
- /var/log
- Log
files from the system and various programs/services, especially login
(/var/log/wtmp, which logs all logins and logouts into the system) and
syslog (/var/log/messages, where all kernel and system program message are
usually stored). Files in /var/log can often grow indefinitely, and may
require cleaning at regular intervals. Something that is now normally
managed via log rotation utilities such as 'logrotate'. This utility
also allows for the automatic rotation compression, removal and mailing of
log files. Logrotate can be set to handle a log file daily, weekly, monthly
or when the log file gets to a certain size. Normally, logrotate runs as a
daily cron job. This is a good place to start troubleshooting general
technical problems.
- /var/log/auth.log
- Record
of all logins and logouts by normal users and system processes.
- /var/log/btmp
- Log
of all attempted bad logins to the system. Accessed via the lastb command.
- /var/log/debug
- Debugging
output from various packages.
- /var/log/dmesg
- Kernel
ring buffer. The content of this file is referred to by the dmesg command.
- /var/log/gdm/
- GDM
log files. Normally a subset of the last X log file. See /var/log/xdm.log
for mode details.
- /var/log/kdm.log
- KDM
log file. Normally a subset of the last X log file. See /var/log/xdm.log for
more details.
- /var/log/messages
- System
logs.
- /var/log/pacct
- Process
accounting is the bookkeeping of process activity. The raw data of process
activity is maintained here. Three commands can be used to access the
contents of this file dump-acct, sa (summary of process accounting) and
lastcomm (list the commands executed on the system).
- /var/log/utmp
- Active
user sessions. This is a data file and as such it can not be viewed
normally. A human-readable form can be created via the dump-utmp command or
through the w, who or users commands.
- /var/log/wtmp
- Log
of all users who have logged into and out of the system. The last command
can be used to access a human readable form of this file. It also lists
every connection and run-level change.
- /var/log/xdm.log
- XDM
log file. Normally subset of the last X startup log and pretty much useless
in light of the details the X logs is able to provide us with. Only consult
this file if you have XDM specific issues otherwise just use the X logfile.
- /var/log/XFree86.0.log,
/var/log/XFree86.?.log
- X startup logfile. An excellent
resource for uncovering problems with X configuration. Log files are
numbered according to when they were last used. For example, the last log
file would be stored in /var/log/XFree86.0.log, the next
/var/log/XFree86.9.log, so on and so forth.
- /var/log/syslog
- The
'system' log file. The contents of this file is managed via the
syslogd daemon which more often than not takes care of all log manipulation
on most systems.
- /var/mail
- Contains
user mailbox files. The mail files take the form
/var/mail/'username' (Note that /var/mail may be a symbolic link to
another directory). User mailbox files in this location are stored in the
standard UNIX mailbox format. The reason for the location of this directory
was to bring the FHS inline with nearly every UNIX implementation (it was
previously located in /var/spool/mail). This change is important for
inter-operability since a single /var/mail is often shared between multiple
hosts and multiple UNIX implementations (despite NFS locking issues).
- /var/opt
- Variable
data of the program packages in /opt must be installed in
/var/opt/'package-name', where 'package-name' is the name of
the subtree in /opt where the static data from an add-on software package is
stored, except where superceded by another file in /etc. No structure is
imposed on the internal arrangement of /var/opt/'package-name'.
- /var/run
- Contains
the process identification files (PIDs) of system services and other
information about the system that is valid until the system is next booted.
For example, /var/run/utmp contains information about users currently logged
in.
- /var/spool
- Holds
spool files, for instance for mail, news, and printing (lpd) and other
queued work. Spool files store data to be processed after the job currently
occupying a device is finished or the appropriate cron job is started. Each
different spool has its own subdirectory below /var/spool, e.g., the cron
tables are stored in /var/spool/cron/crontabs.
- /var/tmp
- Temporary
files that are large or that need to exist for a longer time than what is
allowed for /tmp. (Although the system administrator might not allow very
old files in /var/tmp either.)
- /var/named
- Database
for BIND. The Berkeley Internet Name Domain (BIND) implements an Internet
domain name server. BIND is the most widely used name server software on the
Internet, and is supported by the Internet Software Consortium, www.isc.org.
- /var/yp
- Database
for NIS (Network Information Services). NIS is mostly used to let several
machines in a network share the same account information (eg. /etc/passwd).
NIS was formerly called Yellow Pages (YP).
The following directories, or symbolic links to directories, are
required in /var for FSSTND compliance:
/var/cache Application cache data
/var/lib Variable state information
/var/local Variable data for /usr/local
/var/lock Lock files
/var/log Log files and directories
/var/opt Variable data for /opt
/var/run Data relevant to running processes
/var/spool Application spool data
/var/tmp Temporary files preserved between system reboots
|
Several directories are 'reserved' in the sense that they must
not be used arbitrarily by some new application, since they would conflict
with historical and/or local practice. They are:
/var/backups
/var/cron
/var/msgs
/var/preserve
|
The following directories, or symbolic links to directories, must be in /var,
if the corresponding subsystem is installed:
account Process accounting logs (optional)
crash System crash dumps (optional)
games Variable game data (optional)
mail User mailbox files (optional)
yp Network Information Service (NIS) database files (optional)
|
1.19. /srv
/srv contains site-specific data which is served by this system.
This main purpose of specifying this is so that users may find
the location of the data files for particular service, and so that
services which require a single tree for readonly data, writable data
and scripts (such as cgi scripts) can be reasonably placed. Data that
is only of interest to a specific user should go in that users'
home directory.
The methodology used to name subdirectories of /srv is unspecified as there
is currently no consensus on how this should be done. One method for
structuring data under /srv is by protocol, eg. ftp, rsync, www, and cvs.
On large systems it can be useful to structure /srv by administrative
context, such as /srv/physics/www, /srv/compsci/cvs, etc. This setup will
differ from host to host. Therefore, no program should rely on a specific
subdirectory structure of /srv existing or data necessarily being stored in
/srv. However /srv should always exist on FHS compliant systems and should
be used as the default location for such data.
Distributions must take care not to remove locally placed files in these
directories without administrator permission.
This is particularly important as these areas will often contain both
files initially installed by the distributor, and those added by the
administrator.
|
1.20. /tmp
This directory contains mostly files that are required temporarily. Many
programs use this to create lock files and for temporary storage of data. Do
not remove files from this directory unless you know exactly what you are doing!
Many of these files are important for currently running programs and deleting
them may result in a system crash. Usually it won't contain more than a few KB
anyway. On most systems, this directory is cleared out at boot or at shutdown
by the local system. The basis for this was historical precedent and common
practice. However, it was not made a requirement because system administration
is not within the scope of the FSSTND. For this reason people and programs must
not assume that any files or directories in /tmp are preserved between
invocations of the program. The reasoning behind this is for compliance with
IEEE standard P1003.2 (POSIX, part 2).
Glossary
-
ARPA
-
The Advanced Research and Projects Agency of the United
States Department of Defense. Also known as DARPA (the "D" stands for
"Defense"), it originated in the late 1960s and early 1970s the proposal
and standards for the Internet. For this reason, the Internet was
initially referred to as ARPANet, and connected the military with the
various centers of research around the United States in a way that was
intended to have a high degree of survivability against a nuclear
attack.
-
BASH
-
The Bourne Again Shell and is based on the Bourne shell, sh, the original command interpreter.
-
Bourne Shell
-
The Bourne shell is the original Unix shell (command
execution program, often called a command interpreter) that was
developed at AT&T. Named for its developer, Stephen Bourne, the
Bourne shell is also known by its program name, sh. The shell prompt
(character displayed to indicate readiness for input) used is the $
symbol. The Bourne shell family includes the Bourne, Korn shell, bash,
and zsh shells. Bourne Again Shell (bash) is the free version of the
Bourne shell distributed with Linux systems. Bash is similar to the
original, but has added features such as command line editing. Its name
is sometimes spelled as Bourne Again SHell, the capitalized Hell
referring to the difficulty some people have with it.
-
CLI
-
A CLI (command line interface) is a user interface to a
computer's operating system or an application in which the user
responds to a visual prompt by typing in a command on a specified line,
receives a response back from the system, and then enters another
command, and so forth. The MS-DOS Prompt application in a Windows
operating system is an example of the provision of a command line
interface. Today, most users prefer the graphical user interface (GUI)
offered by Windows, Mac OS, BeOS, and others. Typically, most of today's
Unix-based systems offer both a command line interface and a graphical
user interface.
-
core
-
A core file is created when a program terminates
unexpectedly, due to a bug, or a violation of the operating system's or
hardware's protection mechanisms. The operating system kills the program
and creates a core file that programmers can use to figure out what
went wrong. It contains a detailed description of the state that the
program was in when it died. If would like to determine what program a
core file came from, use the file command, like this: $ file core That
will tell you the name of the program that produced the core dump. You
may want to write the maintainer(s) of the program, telling them that
their program dumped core. To Enable or Disable Core Dumps you must use
the ulimit command in bash, the limit command in tcsh, or the rlimit
command in ksh. See the appropriate manual page for details. This
setting affects all programs run from the shell (directly or
indirectly), not the whole system. If you wish to enable or disable core
dumping for all processes by default, you can change the default
setting in /usr/include/linux/sched.h. Refer to definition of INIT_TASK,
and look also in /usr/include/linux/resource.h. PAM support optimizes
the system's environment, including the amount of memory a user is
allowed. In some distributions this parameter is configurable in the
/etc/security/limits.conf file. For more information, refer to the Linux
Administrator's Security Guide.
-
daemon
-
A process lurking in the background, usually unnoticed,
until something triggers it into action. For example, the \cmd{update}
daemon wakes up every thirty seconds or so to flush the buffer cache,
and the \cmd{sendmail} daemon awakes whenever someone sends mail.
-
DARPA
-
The Defense Advanced Research Projects Agency is the
central research and development organization for the Department of
Defense (DoD). It manages and directs selected basic and applied
research and development projects for DoD, and pursues research and
technology where risk and payoff are both very high and where success
may provide dramatic advances for traditional military roles and
missions.
-
DHCP
-
Dynamic Host Control Protocol, is a protocol like BOOTP
(actually dhcpd includes much of the functionality of BOOTPD). It
assigns IP addresses to clients based on lease times. DHCP is used
extensively by Microsoft and more recently also by Apple. It is probably
essential in any multi-platform environment.
-
DNS
-
Domain Name System translates Internet domain and host
names to IP addresses. DNS implements a distributed database to store
name and address information for all public hosts on the Net. DNS
assumes IP addresses do not change (i.e., are statically assigned rather
than dynamically assigned). The DNS database resides on a hierarchy of
special-purpose servers. When visiting a Web site or other device on the
Net, a piece of software called the DNS resolver (usually built into
the network operating system) first contacts a DNS server to determine
the server's IP address. If the DNS server does not contain the needed
mapping, it will in turn forward the request to a DNS server at the next
higher level in the hierarchy. After potentially several forwarding and
delegation messages are sent within the DNS hierarchy, the IP address
for the given host eventually is delivered to the resolver. DNS also
includes support for caching requests and for redundancy. Most network
operating systems allow one to enter the IP addresses of primary,
secondary, and tertiary DNS servers, each of which can service initial
requests from clients. Many ISPs maintain their own DNS servers and use
DHCP to automatically assign the addresses of these servers to dial-in
clients, so most home users need not be aware of the details behind DNS
configuration. Registered domain names and addresses must be renewed
periodically, and should a dispute occur between two parties over
ownership of a given name, such as in trademarking, ICANN's Uniform
Domain-Name Dispute-Resolution Policy can be invoked. Also known as
Domain Name System, Domain Name Service, Domain Name Server.
-
environment variable
-
A variable that is available to any program that is started by the shell.
-
ESD
-
Enlightened Sound Daemon. This program is designed to
mix together several digitized audio streams for playback by a single
device.
-
filesystem
-
The methods and data structures that an operating
system uses to keep track of files on a disk or partition; the way the
files are organized on the disk. Also used to describe a partition or
disk that is used to store the files or the type of the filesystem.
-
FSSTND
-
Often the group, which creates the Linux File System
Structure document, or the document itself, is referred to as the
'FSSTND'. This is short for "file system standard". This document has
helped to standardize the layout of file systems on Linux systems
everywhere. Since the original release of the standard, most
distributors have adopted it in whole or in part, much to the benefit of
all Linux users. It is now often refered to as the FHS (Filesystem
Hierarchy Standard) document though since its incorporation into the LSB
(Linux Standards Base) Project.
-
GUI
-
Graphical User Interface. The use of pictures rather
than just words to represent the input and output of a program. A
program with a GUI runs under some windowing system (e.g. The X Window
System, Microsoft Windows, Acorn RISC OS, NEXTSTEP). The program
displays certain icons, buttons, dialogue boxes etc. in its windows on
the screen and the user controls it mainly by moving a pointer on the
screen (typically controlled by a mouse) and selecting certain objects
by pressing buttons on the mouse while the pointer is pointing at them.
Though Apple Computer would like to claim they invented the GUI with
their Macintosh operating system, the concept originated in the early
1970s at Xerox's PARC laboratory.
-
hard link
-
A directory entry, which maps a filename to an inode,
number. A file may have multiple names or hard links. The link count
gives the number of names by which a file is accessible. Hard links do
not allow multiple names for directories and do not allow multiple names
in different filesystems.
-
init
-
'init' process is the first user level process started
by the kernel. init has many important duties, such as starting getty
(so that users can log in), implementing run levels, and taking care of
orphaned processes. This chapter explains how init is configured and how
you can make use of the different run levels. init is one of those
programs that are absolutely essential to the operation of a Linux
system, but that you still can mostly ignore. Usually, you only need to
worry about init if you hook up serial terminals, dial-in (not dial-out)
modems, or if you want to change the default run level. When the kernel
has started (has been loaded into memory, has started running, and has
initialized all device drivers and data structures and such), it
finishes its own part of the boot process by starting a user level
program, init. Thus, init is always the first process (its process
number is always 1). The kernel looks for init in a few locations that
have been historically used for it, but the proper location for it is
/sbin/init. If the kernel can't find init, it tries to run /bin/sh, and
if that also fails, the startup of the system fails. When init starts,
it completes the boot process by doing a number of administrative tasks,
such as checking filesystems, cleaning up /tmp, starting various
services, and starting a getty for each terminal and virtual console
where users should be able to log in. After the system is properly up,
init restarts getty for each terminal after a user has logged out (so
that the next user can log in). init also adopts orphan processes: when a
process starts a child process and dies before its child, the child
immediately becomes a child of init. This is important for various
technical reasons, but it is good to know it, since it makes it easier
to understand process lists and process tree graphs. init itself is not
allowed to die. You can't kill init even with SIGKILL. There are a few
variants of init available. Most Linux distributions use sysvinit
(written by Miquel van Smoorenburg), which is based on the System V init
design. The BSD versions of Unix have a different init. The primary
difference is run levels: System V has them, BSD doesn't.
-
inode
-
An inode is the address of a disk block. When you see
the inode information through ls, ls prints the address of the first
block in the file. You can use this information to tell if two files are
really the same file with different names (links). A file has several
components: a name, contents, and administrative information such as
permissions and modification times. The administrative information is
stored in the inode (over the years, the hyphen fell out of "i-node"),
along with essential system data such as how long it is, where on the
disc the contents of the file are stored, and so on. There are three
times in the inode: the time that the contents of the file were last
modified (written); the time that the file was last used (read or
executed); and the time that the inode itself was last changed, for
example to set the permissions. Altering the contents of the file does
not affect its usage time and changing the permissions affects only the
inode change time. It is important to understand inodes, not only to
appreciate the options on ls, but because in a strong sense the inodes
are the files. All the directory hierarchy does is provide convenient
names for files. The system's internal name for the file is its
i-number: the number of the inode holding the file's information.
-
kernel
-
Part of an operating system that implements the interaction with hardware and the sharing of resources.
-
libraries
-
Executables should have no undefined symbols, only
useful symbols; all useful programs refer to symbols they do not define
(eg. printf or write). These references are resolved by pulling object
files from libraries into the executable.
-
link
-
A symbolic link (alias in MacOS and shortcut under
Windows) is a file that points to another file; this is a commonly used
tool. A hard-link rarely created by the user, is a filename that points
to a block of data that has several other filenames as well.
-
man page
-
Every version of UNIX comes with an extensive
collection of online help pages called man pages (short for manual
pages). The man pages are the authoritative documentation about your
UNIX system. They contain complete information about both the kernel and
all the utilities.
-
MTA
-
Mail Transfer Agents. Alongside the web, mail is the
top reason for the popularity of the Internet. E-mail is an inexpensive
and fast method of time-shifted messaging which, much like the Web, is
actually based around sending and receiving plain text files. The
protocol used is called the Simple Mail Transfer Protocol (SMTP). The
server programs that implement SMTP to move mail from one server to
another are called MTAs. Once upon a time users would have to Telnet
into an SMTP server and use a command line mail program like 'mutt' or
'pine' to check their mail. Now, GUI based e-mail clients like Mozilla,
Kmail and Outlook allow users to check their email off of a local SMTP
sever. Additional protocols like POP3 and IMAP4 are used between the
SMTP server and desktop mail client to allow clients to manipulate files
on, and download from, their local mail server. The programs that
implement POP3 and IMAP4 are called Mail Delivery Agents (MDAs). They
are generally separate from MTAs.
-
NFS
-
Network File System, is the UNIX equivalent of Server
Message Block (SMB). It is a way through which different machines can
import and export local files between each other. Like SMB though, NFS
sends information including user passwords unencrypted, so it's best to
limit its usage to within your local network.
-
operating system
-
Software that shares a computer system's resources
(processor, memory, disk space, network bandwidth, and so on) between
users and the application programs they run. Controls access to the
system to provide security.
-
PAM
-
Pluggable Authentication Modules. A suite of shared
libraries that determine how a user will be authenticated. For example,
conventionally UNIX users authenticate themselves by supplying a
password at the password prompt after they have typed their name at the
login prompt. In many circumstances, such as internal access to
workstations, this simple form of authentication is considered
sufficient. In other cases, more information is warranted. If a user
wants to log in to an internal system from an external source, like the
Internet, more or alternative information may be required - perhaps a
one-time password. PAM provides this type of capability and much more.
Most important, PAM modules allow you to configure your environment with
the necessary level of security.
-
PATH
-
The shell looks for commands and programs in a list of
file paths stored in the PATH environment variable. An environment
variable stores information in a place where other programs and commands
can access it. Environment variables store information such as the
shell that you are using, your login name, and your current working
directory. To see a list of all the environment variables currently
defined; type 'set' at the prompt. When you type a command at the shell
prompt, the shell will look for that command's program file in each
directory listed in the PATH variable, in order. The first program found
matching the command you typed will be run. If the command's program
file is not in a directory listed in you PATH environment variable, the
shell returns a "commands not found" error. By default, the shell does
not look in your current working directory or your home directory for
commands This is really a security mechanism so that you don't execute
programs by accident. What if a malicious user put a harmful program
called ls in your home directory? If you typed ls and the shell looked
for the fake program in your home directory before the real program in
the /bin directory, what do you think would happen? If you thought bad
things, you are on the right track. Since your PATH doesn't have the
current directory as one of its search locations, programs in your
current directory must be called with an absolute path of a relative
path specified as './program-name'. To see what directories are part of
your PATH enter this command: # echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11
-
pipes and sockets
-
Special files that programs use to communicate with one
another. They are rarely seen, but you might be able to see a socket or
two in the /dev/ directory.
-
process identifier
-
Shown in the heading of the ps command as PID. The unique number assigned to every process running in the system.
-
rpc
-
Remote Procedure Calls. It enables a system to make
calls to programs such as NFS across the network transparently, enabling
each system to interpret the calls as if they were local. In this case,
it would make exported filesystems appear as thought they were local.
-
set group ID (SGID)
-
The SGID permission causes a script to run with its
group set to the group of the script, rather than the group of the user
who started it. It is normally considered extremely bad practice to run a
program in this way as it can pose many security problems. Later
versions of the Linux kernel will even prohibit the running of shell
scripts that have this attribute set.
-
set user ID (SUID)
-
The SUID permission causes a script to run as the user
who is the owner of the script, rather than the user who started it. It
is normally considered extremely bad practice to run a program in this
way as it can pose many security problems. Later versions of the Linux
kernel will even prohibit the running of shell scripts that have this
attribute set.
-
signal
-
Software interrupts sent to a program to indicate that
an important event has occurred. The events can vary from user requests
to illegal memory access errors. Some signals, like the interrupt
signal, indicate that a user has asked the program to do something that
is not in the usual flow of control.
-
SSH
-
The Secure Shell, or SSH, provides a way of running
command line and graphical applications, and transferring files, over an
encrypted connection, all that will be seen is junk. It is both a
protocol and a suite of small command line applications, which can be
used for various functions. SSH replaces the old Telnet application, and
can be used for secure remote administration of machines across the
Internet. However, it also has other features. SSH increases the ease of
running applications remotely by setting up X permissions
automatically. If you can log into a machine, it allows you to run a
graphical application on it, unlike Telnet, which requires users to have
an understanding of the X authentication mechanisms that are
manipulated through the xauth and xhost commands. SSH also has inbuilt
compression, which allows your graphic applications to run much faster
over the network. SCP (Secure Copy) and SFTP (Secure FTP) allow transfer
of files over the remote link, either via SSH's own command line
utilities or graphical tools like Gnome's GFTP. Like Telnet, SSH is
cross-platform. You can find SSH server and clients for Linux, Unix and
all flavours of Windows, BeOS, PalmOS, Java and embedded Oses used in
routers.
-
STDERR
-
Standard error. A special type of output used for error messages. The file descriptor for STDERR is 2.
-
STDIN
-
Standard input. User input is read from STDIN. The file descriptor for STDIN is 0.
-
STDOUT
-
Standard output. The output of scripts is usually to STDOUT. The file descriptor for STDOUT is 1.
-
symbol table
-
The part of an object table that gives the value of
each symbol (usually as a section name and an offset) is called the
symbol table. Executables may also have a symbol table, with this one
giving the final values of the symbols. Debuggers use the symbol table
to present addresses to the user in a symbolic, rather than a numeric
form. It is possible to strip the symbol table from executables
resulting in a smaller sized executable but this prevents meaningful
debugging.
-
symbolic link or soft link
-
A special filetype, which is a small pointer file,
allowing multiple names for the same file. Unlike hard links, symbolic
links can be made for directories and can be made across filesystems.
Commands that access the file being pointed to are said to follow the
symbolic link. Commands that access the link itself do not follow the
symbolic link.
-
system call
-
The services provided by the kernel to application
programs, and the way in which they are invoked. See section 2 of the
manual pages.
-
system program
-
Programs that implement high level functionality of an
operating system, i.e., things that aren't directly dependent on the
hardware. May sometimes require special privileges to run (e.g., for
delivering electronic mail), but often just commonly thought of as part
of the system (e.g., a compiler).
-
tcp-wrappers
-
Almost all of the services provided through inetd are
invoked through tcp-wrappers by way of the tcp-wrappers daemon, tcpd.
The tcp-wrappers mechanism provides access control list restrictions and
logging for all service requests to the service it wraps. It may be
used for either TCP or TCP services as long as the services are invoked
through a central daemon process such as inetd. These programs log the
client host name of incoming telnet, ftp, rsh, rlogin, finger etc....
requests. Security options are access control per host, domain and/or
service; detection of host name spoofing or host address spoofing; booby
traps to implement an early-warning system.
-
ZSH
-
Zsh was developed by Paul Falstad as a replacement for
both the Bourne and C shell. It incorporates features of all the other
shells (such as file name completion and a history mechanism) as well as
new capabilities. Zsh is considered similar to the Korn shell. Falstad
intended to create in zsh a shell that would do whatever a programmer
might reasonably hope it would do. Zsh is popular with advanced users.
Along with the Korn shell and the C shell, the Bourne shell remains
among the three most widely used and is included with all UNIX systems.
The Bourne shell is often considered the best shell for developing
scripts.
Appendix A. UNIX System V Signals
Symbol Number Action Meaning
SIGHUP 1 exit Hangs up.
SIGINT 2 exit Interrupts.
SIGQUIT 3 core dump Quits.
SIGILL 4 core dump Illegal instruction.
SIGTRAP 5 core dump Trace trap.
SIGIOT 6 core dump IOT instruction.
SIGEMT 7 core dump MT instruction.
SIGFPE 8 core dump Floating point exception.
SIGKILL 9 exit Kills (cannot be caught or ignored).
SIGBUS 10 core dump Bus error.
SIGSEGV 11 core dump Segmentation violation.
SIGSYS 12 core dump Bad argument to system call.
SIGPIPE 13 exit Writes on a pipe with no one to read it.
SIGALRM 14 exit Alarm clock.
SIGTERM 15 exit Software termination signal.
|
Appendix B. Sources
- The UNIX programming environment, Brian W. Kernighan, Rob Pike, Prentice Hall, New Jersey, 1984.
- Newnes UNIX Pocket Book, Steve Heath, Butterworth-Heinemann, Great Britain, 1998.
- Suse Linux Installation and Configuration, Nazeeh Amin El-Dirghami & Youssef A. Abu Kwaik, QUE Corporation, USA, 2000.
- Inside Linux, Michael J. Tobler, New Riders Publishing, USA, 2001.
- Linux in a Nutshell 2nd Edition, Ellen Siever, O'Reilly & Associates Inc., CA, USA, 1999
- Using Caldera OpenLinux Special Edition, Allan Smart, Erik Ratcliffe, Tim Bird, David Bandel, QUE Corporation, USA, 1999.
- Linux
System Security (The Administrator's Guide to Open Source Security
Tools), Scott Mann & Ellen L. Mitchell, Prentice-Hall, New-Jersey,
2000.
- XFree86 For Linux (Uncommon Solutions for the Technical Professional), Aron Hsiao, QUE Corporation, USA, 1999.
- Complete Idiot's Guide to Linux Second Edition, Manuel Alberto Ricart, QUE Corporation, USA, 1999.
- Lions' Commentary on UNIX 6th Edition with Source Code, John Lions, Peer-to-Peer Communications Incorporated, USA, 1996.
- The Linux System Administrators' Guide Version 0.6.1, Lars Wirzenius, liw@iki.fi, Finland, 1998.
- SAMS Teach Yourself Shell Programming in 24 Hours, Sriranga Veerararaghavan, SAMS Publishing, USA, 1999.
- 433-252
Software Development: Principles and Tools, Zoltan Somogyi, Les
Kitchen, The University of Melbourne, Department of Computer Science and
Software Engineering, Australia, 2002.
- The Advanced Linux Pocketbook, Ashton Mills, ashtonmills@bigpond.com, ACP Publishing Pty Ltd, Australia, 2001.
- http://www.pathname.com/fhs
- http://www.atnf.csiro.au/people/rgooch/linux/docs/devfs.html
- http://freeos.com/articles/3102/
- http://freeos.com/articles/2879/
- http://www.linuxjournal.com/article.php?sid=1104
- http://www.mlinux.org/projects/present/filesys/slide01.html
- http://www.mil.ufl.edu/linuxhelp/linuxfilesystem.pdf
- http://www.nsa.gov/selinux/doc/slinux/node57.html
- http://www.linuxnow.com/tutorial/fs/fs.html
- http://info.cqu.edu.au/courses/aut2001/85321/resources/study_guide/chapter_4
- http://lwn.net/2001/features/ols/pdf/pdf/devfs.pdf
- /usr/src/linux/Documentation/filesystems/proc.txt,
Terrehon Bowden <terrehon@pacbell.net>, Bodo Bauer
<bb@ricochet.net>, Jorge Nerin <comandante@zaralinux.com>
- /usr/share/doc/FAQ/Linux-FAQ/index.html,
ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/comp/os/linux/misc/, David
Merrill, david -AT- lupercalia.net, Robert Kiesling,
rkiesling@mainmatter.com, Linux Frequently Asked Questions with Answers,
2001-12-04.
- /usr/share/doc/sysvinit/README.runlevels.gz
- /usr/src/linux/Documentation/initrd.txt,
Werner Almesberger <werner.almesberger@epfl.ch> and Hans Lermen
<lermen@fgan.de>, 2000.
- http://www.opussoftware.com/tutorial/TutMakefile.htm
- http://www.cc.gatech.edu/people/home/oxblood/Linux_Doc.txt
- http://users.erols.com/mmmcd/lilo/boot_sequence.html
- hints.linuxfromscratch.org/hints/grub-howto.txt
- http://www.fifi.org/cgi-bin/man2html?initrd+4
- http://www.linuxsa.org.au/meetings/1997-06/fsstnd/fsstnd.html
- http://public.csusm.edu/public/guests/history/netinfo/arpa.html
- http://whatis.techtarget.com/definition/0,,sid9_gci214635,00.html
- http://whatis.techtarget.com/definition/0,,sid9_gci213627,00.html
- http://hostingworks.com/support/dict.phtml?foldoc=Defense%2BAdvanced%2BResearch%2BProjects%2BAgency
- http://www.linuxsa.org.au/meetings/1997-06/fsstnd/fsstnd.html
- http://compnetworking.about.com/library/glossary/bldef-dns.htm
- http://www.scala.com/definition/graphical-user-interface.html
- http://hostingworks.com/support/dict.phtml?foldoc=Graphical+User+Interface
- http://www.mostang.com/sane/intro.html
Appendix C. About the Author
Binh Nguyen was born, 26 March 1983, Melbourne, Victoria. He studied
at St Josephs Marist Brothers College, North Fitzroy until receiving a
scholarship to St Kevin's College, Toorak in 1998.
He is currently a university undergraduate studying computer science
and physics at the University of Melbourne. His main interests in each
area are in Operating Systems and Quantum Mechanics respectively.
His background is strongly biased towards science and mathematics.
Nonetheless, he does have an appreciation for the arts, humanities
and sport. A reasonably proficient musician (flute), he is currently
pondering whether he should complete his musical studies to obtain a
diploma so that he can teach. In high school, he was a member of the
athletics, basketball, football, cricket and swimming squads. He speaks
English predominately but is also able to communicate in Vietnamese and
French. When younger he also possessed the ability to communicate in
Chinese and Italian.
Although brought up as a Buddhist and studying at Catholic/Christian
schools all his life as well as studying scripture during his final year of
high school he considers himself an atheist.
At this moment in time, he works part-time as a (commercial)
researcher/developer on Linux related projects with his current
focus being on software distribution mechanisms.
Two of his technical documents have been incorporated into the
Linux Documentation Project ("Linux Dictionary" and "Linux Filesystem
Hierarchy",
www.tldp.org/guides.html). Furthermore, they are being
used as reference books in at least ten universities around the world
(University of Southern Queensland (Australia),
Universidad Michoacana (Mexico),
Hong Kong Polytechnic University (Hong Kong),
Universidade de Sao Paolo (Brazil),
University of Southern California (United States of America),
University of Wales Swansea (United Kingdom),
University of Ulster (Ireland),
Universität Duisburg-Essen (Germany),
Universidad Rey Juan Carlos (Spain),
Insituto Superior Miguel Torga (Portugal),
and Universiti Sains Malaysia (Malaysia)). As well as this, he is also a
Development Lead and Project Administrator of the "Computer Dictionary
Project"
http://computerdictionary.tsf.org.za/dictionary/index.html
which is being supported by the Shuttleworth Foundation.
He has published articles at linux.com, linmagau.org, desktoplinux.com,
newsforge.com, linuxtoday.com, linux.org, pclinuxonline.com,
tuxreports.com, etc.... and has a keen interest in the latest innovations
in science and technology.
The author's homepage is at,
http://geocities.com/linuxfilesystem/
Appendix D. Contributors
The author would like to thank a group of members (who wish to remain anonymous) from MLUG
http://www.mlug.org.au for having the time
and patience to help proof read this document before going to publication.
Appendix E. Disclaimer
No liability for the contents of this document can be accepted.
Use the concepts, examples and other content at your own risk.
As this is a new edition of this document, there may be errors
and inaccuracies that may of course be damaging to your system.
Proceed with caution, and although this is highly unlikely, the
author does not and can not take any responsibility for any damage
to your system that may occur as a direct or indirect result of
information that is contained within this document.
Naming of particular products or brands should not be seen as endorsements.
You are strongly recommended to make a backup of your system before major
installation and adhere to the practice of backing up at regular intervals.
Appendix F. Donations
If you would like to make a donations towards this project
please use Paypal,
https://www.paypal.com.
Appendix G. Feedback
Further revisions of this document will be dependent upon user response.
Any feedback on the content of this document is welcome. Every attempt has
been made to ensure that the instructions and information herein are
accurate and reliable. Send comments, corrections, suggestions and questions
to the author Binh Nguyen, linuxfilesystem(at)yahoo(dot)com(dot)au with the
subject heading of LHFS. There is however, no guarantee of response.
All trademarks and copyrights are the property of their owners, unless
otherwise indicated. Use of a term in this document should not be regarded
as affecting the validity of any trademark or service mark.
The author would appreciate and consider it courteous, notification of
any and all modifications, translations, and printed versions.
Appendix H. GNU Free Documentation License
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
H.1. PREAMBLE
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other functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it, with
or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible for
modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft license
designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals; it
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number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above,
and you may publicly display copies.
H.4. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover Texts:
Front-Cover Texts on the front cover, and Back-Cover Texts on the back
cover. Both covers must also clearly and legibly identify you as the
publisher of these copies. The front cover must present the full title
with all words of the title equally prominent and visible. You may add
other material on the covers in addition. Copying with changes limited
to the covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in other
respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a machine-readable
Transparent copy along with each Opaque copy, or state in or with each
Opaque copy a computer-network location from which the general
network-using public has access to download using public-standard
network protocols a complete Transparent copy of the Document, free of
added material. If you use the latter option, you must take reasonably
prudent steps, when you begin distribution of Opaque copies in quantity,
to ensure that this Transparent copy will remain thus accessible at the
stated location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or retailers)
of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of copies, to
give them a chance to provide you with an updated version of the
Document.
H.5. MODIFICATIONS
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with the
Modified Version filling the role of the Document, thus licensing
distribution and modification of the Modified Version to whoever
possesses a copy of it. In addition, you must do these things in the
Modified Version:
- Use in the Title Page (and on the covers, if any) a
title distinct from that of the Document, and from those of previous
versions (which should, if there were any, be listed in the History
section of the Document). You may use the same title as a previous
version if the original publisher of that version gives permission.
- List on the Title Page, as authors, one or more
persons or entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the principal
authors of the Document (all of its principal authors, if it has fewer
than five), unless they release you from this requirement.
- State on the Title page the name of the publisher of
the Modified Version, as the publisher.
- Preserve all the copyright notices of the Document.
- Add an appropriate copyright notice for your
modifications adjacent to the other copyright notices.
- Include, immediately after the copyright notices, a
license notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in the
Addendum below.
- Preserve in that license notice the full lists of
Invariant Sections and required Cover Texts given in the Document's
license notice.
- Include an unaltered copy of this License.
- Preserve the section Entitled "History", Preserve its
Title, and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on the Title
Page. If there is no section Entitled "History" in the Document,
create one stating the title, year, authors, and publisher of the
Document as given on its Title Page, then add an item describing the
Modified Version as stated in the previous sentence.
- Preserve the network location, if any, given in the
Document for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for previous
versions it was based on. These may be placed in the "History"
section. You may omit a network location for a work that was
published at least four years before the Document itself, or if the
original publisher of the version it refers to gives permission.
- For any section Entitled "Acknowledgements" or
"Dedications", Preserve the Title of the section, and preserve in the
section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
- Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers or the
equivalent are not considered part of the section titles.
- Delete any section Entitled "Endorsements".
Such a section may not be included in the Modified Version.
- Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant Section.
- Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section Entitled "Endorsements", provided it
contains nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end of the
list of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or through
arrangements made by) any one entity. If the Document already includes
a cover text for the same cover, previously added by you or by
arrangement made by the same entity you are acting on behalf of, you may
not add another; but you may replace the old one, on explicit permission
from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.
H.6. COMBINING DOCUMENTS
You may combine the Document with other documents released under
this License, under the terms defined in section
4 above for modified versions, provided that you include in the
combination all of the Invariant Sections of all of the original
documents, unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all their
Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by adding
at the end of it, in parentheses, the name of the original author or
publisher of that section if known, or else a unique number. Make the
same adjustment to the section titles in the list of Invariant Sections
in the license notice of the combined work.
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You must
delete all sections Entitled "Endorsements".
H.7. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual copies
of this License in the various documents with a single copy that is
included in the collection, provided that you follow the rules of this
License for verbatim copying of each of the documents in all other
respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert a
copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.
H.8. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of a
storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the legal
rights of the compilation's users beyond what the individual works
permit. When the Document is included in an aggregate, this License does
not apply to the other works in the aggregate which are not themselves
derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on covers
that bracket the Document within the aggregate, or the electronic
equivalent of covers if the Document is in electronic form. Otherwise
they must appear on printed covers that bracket the whole
aggregate.
H.9. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers. In case of a disagreement between the
translation and the original version of this License or a notice or
disclaimer, the original version will prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve its
Title (section 1) will typically require changing the actual
title.
H.10. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided for under this License. Any other attempt
to copy, modify, sublicense or distribute the Document is void, and will
automatically terminate your rights under this License. However,
parties who have received copies, or rights, from you under this License
will not have their licenses terminated so long as such parties remain
in full compliance.
H.11. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns. See
http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered version of
this License "or any later version" applies to it, you have the option
of following the terms and conditions either of that specified version
or of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.
H.12. ADDENDUM: How to use this License for
your documents
To use this License in a document you have written, include a copy
of the License in the document and put the following copyright and
license notices just after the title page:
Copyright (c) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled "GNU
Free Documentation License".
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with the
Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.
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