


                                   - 1 -






                  Filesystem Hierarchy Standard -- Version 2.2 final

                         Filesystem Hierarchy Standard Group
                      edited by Rusty Russell and Daniel Quinlan


                                       ABSTRACT

                 This standard consists of a set of requirements and
            guidelines for file and directory placement under UNIX-like
            operating systems.  The guidelines are intended to support
            interoperability of applications, system administration tools,
            development tools, and scripts as well as greater uniformity
            of documentation for these systems.


       May 23, 2001










































       Filesystem Hierarchy Standard                               May 23, 2001



       All trademarks and copyrights are owned by their owners, unless
       specifically noted otherwise.  Use of a term in this document should not
       be regarded as affecting the validity of any trademark or service mark.

































       Copyright (C) 1994-2001 Daniel Quinlan

       Copyright (C) 2001 Paul `Rusty' Russell

       Permission is granted to make and distribute verbatim copies of this
       standard provided the copyright and this permission notice are preserved
       on all copies.
       Permission is granted to copy and distribute modified versions of this
       standard under the conditions for verbatim copying, provided also that
       the title page is labeled as modified including a reference to the
       original standard, provided that information on retrieving the original
       standard is included, and provided that the entire resulting derived
       work is distributed under the terms of a permission notice identical to
       this one.

       Permission is granted to copy and distribute translations of this
       standard into another language, under the above conditions for modified
       versions, except that this permission notice may be stated in a
       translation approved by the copyright holder.

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       1.  Introduction

       1.1  Purpose

       This standard enables

          o Software to predict the location of installed files and
            directories, and

          o Users to predict the location of installed files and directories.

       We do this by

          o Specifying guiding principles for each area of the filesystem,

          o Specifying the minimum files and directories required,

          o Enumerating exceptions to the principles, and

          o Enumerating specific cases where there has been historical
            conflict.

       The FHS document is used by

          o Independent software suppliers to create applications which are FHS
            compliant, and work with distributions which are FHS complaint,

          o OS creators to provide systems which are FHS compliant, and

          o Users to understand and maintain the FHS compliance of a system.

       1.2  Conventions

       We recommend that you read a typeset version of this document rather
       than the plain text version.  In the typeset version, the names of files
       and directories are displayed in a constant-width font.

       Components of filenames that vary are represented by a description of
       the contents enclosed in "<" and ">" characters, <thus>.  Electronic
       mail addresses are also enclosed in "<" and ">" but are shown in the
       usual typeface.

       Optional components of filenames are enclosed in "[" and "]" characters
       and may be combined with the "<" and ">" convention.  For example, if a
       filename is allowed to occur either with or without an extension, it
       might be represented by <filename>[.<extension>].

       Variable substrings of directory names and filenames are indicated by
       "*".







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       2.  The Filesystem

       This standard assumes that the operating system underlying an FHS-
       compliant file system supports the same basic security features found in
       most UNIX filesystems.

       It is possible to define two independent categories of files: shareable
       vs. unshareable and variable vs. static.  There should be a simple and
       easily understandable mapping from directories to the type of data they
       contain: directories may be mount points for other filesystems with
       different characteristics from the filesystem on which they are mounted.

       Shareable data is that which can be shared between several different
       hosts; unshareable is that which must be specific to a particular host.
       For example, user home directories are shareable data, but device lock
       files are not.

       Static data includes binaries, libraries, documentation, and anything
       that does not change without system administrator intervention; variable
       data is anything else that does change without system administrator
       intervention.

       BEGIN RATIONALE
       The distinction between shareable and unshareable data is needed for
       several reasons:

          o In a networked environment (i.e., more than one host at a site),
            there is a good deal of data that can be shared between different
            hosts to save space and ease the task of maintenance.

          o In a networked environment, certain files contain information
            specific to a single host.  Therefore these filesystems cannot be
            shared (without taking special measures).

          o Historical implementations of UNIX-like filesystems interspersed
            shareable and unshareable data in the same hierarchy, making it
            difficult to share large portions of the filesystem.

       The "shareable" distinction can be used to support, for example:

          o A /usr partition (or components of /usr) mounted (read-only)
            through the network (using NFS).

          o A /usr partition (or components of /usr) mounted from read-only
            media.  A CD-ROM is one copy of many identical ones distributed to
            other users by the postal mail system and other methods.  It can
            thus be regarded as a read-only filesystem shared with other FHS-
            compliant systems by some kind of "network".

       The "static" versus "variable" distinction affects the filesystem in two
       major ways:

          o Since / contains both variable and static data, it needs to be
            mounted read-write.


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          o Since the traditional /usr contains both variable and static data,
            and since we may want to mount it read-only (see above), it is
            necessary to provide a method to have /usr mounted read-only.  This
            is done through the creation of a /var hierarchy that is mounted
            read-write (or is a part of another read-write partition, such as
            /), taking over much of the /usr partition's traditional
            functionality.

       Here is a summarizing chart.  This chart is only an example for a common
       FHS-compliant system, other chart layouts are possible within FHS-
       compliance.

                      +---------+-----------------+-------------+
                      |         | shareable       | unshareable |
                      +---------+-----------------+-------------+
                      |static   | /usr            | /etc        |
                      |         | /opt            | /boot       |
                      +---------+-----------------+-------------+
                      |variable | /var/mail       | /var/run    |
                      |         | /var/spool/news | /var/lock   |
                      +---------+-----------------+-------------+
       END RATIONALE


































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       3.  The Root Filesystem

       3.1  Purpose

       The contents of the root filesystem must be adequate to boot, restore,
       recover, and/or repair the system.

          o To boot a system, enough must be present on the root partition to
            mount other filesystems.  This includes utilities, configuration,
            boot loader information, and other essential start-up data.  /usr,
            /opt, and /var are designed such that they may be located on other
            partitions or filesystems.

          o To enable recovery and/or repair of a system, those utilities
            needed by an experienced maintainer to diagnose and reconstruct a
            damaged system must be present on the root filesystem.

          o To restore a system, those utilities needed to restore from system
            backups (on floppy, tape, etc.) must be present on the root
            filesystem.

       BEGIN RATIONALE

       The primary concern used to balance these considerations, which favor
       placing many things on the root filesystem, is the goal of keeping root
       as small as reasonably possible.  For several reasons, it is desirable
       to keep the root filesystem small:

          o It is occasionally mounted from very small media.

          o The root filesystem contains many system-specific configuration
            files.  Possible examples include a kernel that is specific to the
            system, a specific hostname, etc.  This means that the root
            filesystem isn't always shareable between networked systems.
            Keeping it small on servers in networked systems minimizes the
            amount of lost space for areas of unshareable files.  It also
            allows workstations with smaller local hard drives.

          o While you may have the root filesystem on a large partition, and
            may be able to fill it to your heart's content, there will be
            people with smaller partitions.  If you have more files installed,
            you may find incompatibilities with other systems using root
            filesystems on smaller partitions.  If you are a developer then you
            may be turning your assumption into a problem for a large number of
            users.

          o Disk errors that corrupt data on the root filesystem are a greater
            problem than errors on any other partition.  A small root
            filesystem is less prone to corruption as the result of a system
            crash.

       Software must never create or require special files or subdirectories in
       the root directory.  Other locations in the FHS hierarchy provide more
       than enough flexibility for any package.


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       There are several reasons why introducing a new subdirectory of the root
       filesystem is prohibited:

          o It demands space on a root partition which the system administrator
            may want kept small and simple for either performance or security
            reasons.

          o It evades whatever discipline the system administrator may have set
            up for distributing standard file hierarchies across mountable
            volumes.

       END RATIONALE

       3.2  Requirements

       The following directories, or symbolic links to directories, are
       required in /.
       / -- the root directory
       +-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
       +-mnt       Mount point for mounting a filesystem temporarily
       +-opt       Add-on application software packages
       +-sbin      Essential system binaries
       +-tmp       Temporary files
       +-usr       Secondary hierarchy
       +-var       Variable data
       Each directory listed above is specified in detail in separate
       subsections below.  /usr and /var each have a complete section in this
       document due to the complexity of those directories.


       3.3  Specific Options

       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 specified in detail in separate
       subsections below.


       3.4  /bin : Essential user command binaries (for use by all users)

       3.4.1  Purpose

       /bin contains commands that may be used by both the system administrator
       and by users, but which are required when no other filesystems are
       mounted (e.g. in single user mode).  It may also contain commands which
       are used indirectly by scripts.1


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       3.4.2  Requirements

       There must be no subdirectories in /bin.

       The following commands, or symbolic links to commands, are required in
       /bin.

       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 [ and test commands must be placed together in either /bin or
       /usr/bin.



       ____________________

       1. Command  binaries  that  are  not essential enough to place into /bin
          must be placed in /usr/bin, instead.  Items that are required only by
          non-root  users  (the  X Window System, chsh, etc.) are generally not
          essential enough to be placed into the root partition.

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       BEGIN RATIONALE
       For example bash behaves differently when called as sh or bash.  The use
       of a symbolic link also allows users to easily see that /bin/sh is not a
       true Bourne shell.

       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.

       END RATIONALE

       3.4.3  Specific Options

       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.

       BEGIN RATIONALE
       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.

       END RATIONALE

       3.5  /boot : Static files of the boot loader

       3.5.1  Purpose

       This directory contains everything required for the boot process except
       configuration files and the map installer.  Thus /boot stores data that
       is used before the kernel begins executing user-mode programs.  This may
       include saved master boot sectors, sector map files, and other data that
       is not directly edited by hand.2

       3.5.2  Specific Options



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       The operating system kernel must be located in either / or /boot.3

       3.6  /dev : Device files

       3.6.1  Purpose

       The /dev directory is the location of special or device files.

       3.6.2  Specific Options

       If it is possible that devices in /dev will need to be manually created,
       /dev must contain a command named MAKEDEV, which can create devices as
       needed.  It may also contain a MAKEDEV.local for any local devices.

       If required, MAKEDEV must have provisions for creating any device that
       may be found on the system, not just those that a particular
       implementation installs.

       3.7  /etc : Host-specific system configuration

       3.7.1  Purpose

       /etc contains configuration files and directories that are specific to
       the current system.4

       3.7.2  Requirements

       No binaries may be located under /etc.

       The following directories, or symbolic links to directories are required
       in /etc:
       /etc -- Host-specific system configuration
       +-opt       Configuration for /opt

       3.7.3  Specific Options


       ____________________

       2. Programs  necessary to arrange for the boot loader to be able to boot
          a file must be placed in /sbin.  Configuration files for boot loaders
          must be placed in /etc.

       3. On some i386 machines, it may be necessary for /boot to be located on
          a separate partition located completely below cylinder  1024  of  the
          boot device due to hardware constraints.

          Certain  MIPS systems require a /boot partition that is a mounted MS-
          DOS filesystem or whatever other filesystem type  is  accessible  for
          the firmware.  This may result in restrictions with respect to usable
          filenames within /boot (only for affected systems).

       4. The setup of command scripts invoked at boot time may resemble System
          V, BSD or other models.  Further specification in this  area  may  be
          added to a future version of this standard.

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       The following directories, or symbolic links to directories must be in
       /etc, if the corresponding subsystem is installed:
       /etc -- Host-specific system configuration
       +-X11       Configuration for the X Window System (optional)
       +-sgml      Configuration for SGML and XML (optional)
       The following files, or symbolic links to files, must be in /etc if the
       corresponding subsystem is installed:5

       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.6

       3.7.4  /etc/opt : Configuration files for /opt



       ____________________

       5. Systems that use the  shadow  password  suite  will  have  additional
          configuration  files in /etc (/etc/shadow and others) and programs in
          /usr/sbin (useradd, usermod, and others).

       6. On  some  Linux systems, this may be a symbolic link to /proc/mounts,
          in which case this exception is not required.

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       3.7.4.1  Purpose

       Host-specific configuration files for add-on application software
       packages must be installed within the directory /etc/opt/<package>,
       where <package> is the name of the subtree in /opt where the static data
       from that package is stored.

       3.7.4.2  Requirements

       No structure is imposed on the internal arrangement of
       /etc/opt/<package>.

       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/<package>.

       BEGIN RATIONALE
       Refer to the rationale for /opt.

       END RATIONALE

       3.7.5  /etc/X11 : Configuration for the X Window System (optional)

       3.7.5.1  Purpose

       /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.

       3.7.5.2  Specific Options

       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.7 We
       recommend 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.

       3.7.6  /etc/sgml : Configuration files for SGML and XML (optional)



       ____________________

       7. /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.

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       3.7.6.1  Purpose

       Generic configuration files defining high-level parameters of the SGML
       or XML 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.

       3.8  /home : User home directories (optional)

       3.8.1  Purpose

       /home is a fairly standard concept, but it is clearly a site-specific
       filesystem.8 The setup will differ from host to host.  Therefore, no
       program should rely on this location.9

       3.9  /lib : Essential shared libraries and kernel modules

       3.9.1  Purpose

       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.10

       3.9.2  Requirements

       At least one of each of the following filename patterns are required
       (they may be files, or symbolic links):


       ____________________

       8. 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.

       9. 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.

       10.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.

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       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.11

       3.9.3  Specific Options

       The following directories, or symbolic links to directories, must be in
       /lib, if the corresponding subsystem is installed:
       /lib -- essential shared libraries and kernel modules
       +-modules   Loadable kernel modules (optional)
       3.10  /lib<qual> : Alternate format essential shared libraries
       (optional)

       3.10.1  Purpose

       There may be one or more variants of the /lib directory on systems which
       support more than one binary format requiring separate libraries.12

       3.10.2  Requirements

       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.13

       3.11  /mnt : Mount point for a temporarily mounted filesystem

       3.11.1  Purpose

       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.

       3.12  /opt : Add-on application software packages


       ____________________

       11.The       usual       placement      of      this      binary      is
          /usr/lib/gcc-lib/<target>/<version>/cpp.  /lib/cpp can  either  point
          at this binary, or at any other reference to this binary which exists
          in the filesystem.  (For example, /usr/bin/cpp is also often used.)

       12.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.

       13./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).

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       3.12.1  Purpose

       /opt is reserved for the installation of add-on application software
       packages.

       A package to be installed in /opt must locate its static files in a
       separate /opt/<package> directory tree, where <package> is a name that
       describes the software package.

       3.12.2  Requirements

       /opt -- Add-on application software packages
       +-<package> Static package objects
       The directories /opt/bin, /opt/doc, /opt/include, /opt/info, /opt/lib,
       and /opt/man 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 local system administrator,
       but must function normally in the absence of these reserved directories.

       Programs to be invoked by users must be located in the directory
       /opt/<package>/bin. If the package includes UNIX manual pages, they must
       be located in /opt/<package>/man and the same substructure as
       /usr/share/man must be used.

       Package files that are variable (change in normal operation) must be
       installed in /var/opt.  See the section on /var/opt for more
       information.

       Host-specific configuration files must be installed in /etc/opt.  See
       the section on /etc for more information.

       No other package files may 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 must be placed in /var/lock
       and devices must be located 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.

       BEGIN RATIONALE
       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),
       provides for an /opt structure very similar to the one defined here.

       The Intel Binary Compatibility Standard v. 2 (iBCS2) also provides a
       similar structure for /opt.

       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.


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       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.

       END RATIONALE

       3.13  /root : Home directory for the root user (optional)

       3.13.1  Purpose

       The root account's home directory may be determined by developer or
       local preference, but this is the recommended default location.14

       3.14  /sbin : System binaries

       3.14.1  Purpose

       Utilities used for system administration (and other root-only commands)
       are stored in /sbin, /usr/sbin, and /usr/local/sbin.  /sbin contains
       binaries essential for booting, restoring, recovering, and/or repairing
       the system in addition to the binaries in /bin.15 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.16

       3.14.2  Requirements

       The following commands, or symbolic links to commands, are required in
       /sbin.

       shutdown   Command to bring the system down.

       3.14.3  Specific Options

       The following files, or symbolic links to files, must be in /sbin if the
       corresponding subsystem is installed:



       ____________________

       14.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.

       15.Originally, /sbin binaries were kept in /etc.

                                        - 16 -





       Filesystem Hierarchy Standard                               May 23, 2001



       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)

       3.15  /tmp : Temporary files

       3.15.1  Purpose

       The /tmp directory must be made available for programs that require
       temporary files.

       Programs must not assume that any files or directories in /tmp are
       preserved between invocations of the program.

       BEGIN RATIONALE
       IEEE standard P1003.2 (POSIX, part 2) makes requirements that are
       similar to the above section.

       Although data stored in /tmp may be deleted in a site-specific manner,

       ____________________

       16.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.

                                        - 17 -





       Filesystem Hierarchy Standard                               May 23, 2001



       it is recommended that files and directories located in /tmp be deleted
       whenever the system is booted.

       FHS added this recommendation on the basis of historical precedent and
       common practice, but did not make it a requirement because system
       administration is not within the scope of this standard.

       END RATIONALE
















































                                        - 18 -





       Filesystem Hierarchy Standard                               May 23, 2001



       4.  The /usr Hierarchy

       4.1  Purpose

       /usr is the second major section of the filesystem.  /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.

       4.2  Requirements

       The following directories, or symbolic links to directories, are
       required in /usr.
       /usr -- Secondary Hierarchy
       +-bin       Most user commands
       +-include   Header files included by C programs
       +-lib       Libraries
       +-local     Local hierarchy (empty after main installation)
       +-sbin      Non-vital system binaries
       +-share     Architecture-independent data

       4.3  Specific Options

       /usr -- Secondary Hierarchy
       +-X11R6     X Window System, version 11 release 6 (optional)
       +-games     Games and educational binaries (optional)
       +-lib<qual> Alternate Format Libraries (optional)
       +-src       Source code (optional)
       An exception is made for the X Window System because of considerable
       precedent and widely-accepted practice.

       The following symbolic links to directories may be present. This
       possibility is based on the need to preserve compatibility with older
       systems until all implementations can be assumed to use the /var
       hierarchy.

           /usr/spool -> /var/spool
           /usr/tmp -> /var/tmp
           /usr/spool/locks -> /var/lock

       Once a system no longer requires any one of the above symbolic links,
       the link may be removed, if desired.

       4.4  /usr/X11R6 : X Window System, Version 11 Release 6 (optional)

       4.4.1  Purpose

       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


                                        - 19 -





       Filesystem Hierarchy Standard                               May 23, 2001



       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.

       4.4.2  Specific Options

       Host-specific data in /usr/X11R6/lib/X11 should be interpreted as a
       demonstration file.  Applications requiring information about the
       current host must reference a configuration file in /etc/X11, which may
       be linked to a file in /usr/X11R6/lib.17

       4.5  /usr/bin : Most user commands

       4.5.1  Purpose

       This is the primary directory of executable commands on the system.

       4.5.2  Specific Options

       The following directories, or symbolic links to directories, must be in
       /usr/bin, if the corresponding subsystem is installed:
       /usr/bin -- Binaries that are not needed in single-user mode
       +-mh        Commands for the MH mail handling system (optional)
       /usr/bin/X11 must be a symlink to /usr/X11R6/bin if the latter exists.

       The following files, or symbolic links to files, must be in /usr/bin, if
       the corresponding subsystem is installed:

       perl     The Practical Extraction and Report Language (optional)
       python   The Python interpreted language (optional)
       tclsh    Simple shell containing Tcl interpreter (optional)
       wish     Simple Tcl/Tk windowing shell (optional)
       expect   Program for interactive dialog (optional)

       BEGIN RATIONALE
       Because shell script interpreters (invoked with #!<path> on the first
       line of a shell script) cannot rely on a path, it is advantageous to
       standardize their locations.  The Bourne shell and C-shell interpreters
       are already fixed in /bin, but Perl, Python, and Tcl are often found in
       many different places.  They may be symlinks to the physical location of
       the shell interpreters.

       ____________________

       17.Examples of such configuration files include Xconfig, XF86Config,  or
          system.twmrc)

                                        - 20 -





       Filesystem Hierarchy Standard                               May 23, 2001



       END RATIONALE

       4.6  /usr/include : Directory for standard include files.

       4.6.1  Purpose

       This is where all of the system's general-use include files for the C
       programming language should be placed.

       4.6.2  Specific Options

       The following directories, or symbolic links to directories, must be in
       /usr/include, if the corresponding subsystem is installed:
       /usr/include -- Include files
       +-bsd       BSD compatibility include files (optional)
       The symbolic link /usr/include/X11 must link to /usr/X11R6/include/X11
       if the latter exists.

       4.7  /usr/lib : Libraries for programming and packages

       4.7.1  Purpose

       /usr/lib includes object files, libraries, and internal binaries that
       are not intended to be executed directly by users or shell scripts.18

       Applications may use a single subdirectory under /usr/lib.  If an
       application uses a subdirectory, all architecture-dependent data
       exclusively used by the application must be placed within that
       subdirectory.19

       4.7.2  Specific Options

       For historical reasons, /usr/lib/sendmail must be a symbolic link to
       /usr/sbin/sendmail if the latter exists.20

       If /lib/X11 exists, /usr/lib/X11 must be a symbolic link to /lib/X11, or
       to whatever /lib/X11 is a symbolic link to.21

       4.8  /usr/lib<qual> : Alternate format libraries (optional)


       ____________________

       18.Miscellaneous  architecture-independent  application-specific  static
          files and subdirectories must be placed in /usr/share.

       19.For example, the perl5 subdirectory for Perl 5 modules and libraries.

       20.Some executable commands such as makewhatis and  sendmail  have  also
          been  traditionally  placed  in  /usr/lib.  makewhatis is an internal
          binary and must be placed in a binary directory;  users  access  only
          catman.   Newer  sendmail  binaries  are  now  placed  by  default in
          /usr/sbin.  Additionally, systems using  a  sendmail-compatible  mail
          transfer  agent must provide /usr/sbin/sendmail as a symbolic link to
          the appropriate executable.

                                        - 21 -





       Filesystem Hierarchy Standard                               May 23, 2001



       4.8.1  Purpose

       /usr/lib<qual> performs the same role as /usr/lib for an alternate
       binary format, except that the symbolic links /usr/lib<qual>/sendmail
       and /usr/lib<qual>/X11 are not required.22

       4.9  /usr/local : Local hierarchy

       4.9.1  Purpose

       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.23

       4.9.2  Requirements

       The following directories, or symbolic links to directories, must be in
       /usr/local
       /usr/local -- Local hierarchy
       +-bin       Local binaries
       +-games     Local game binaries
       +-include   Local C header files
       +-lib       Local libraries
       +-man       Local online manuals
       +-sbin      Local system binaries
       +-share     Local architecture-independent hierarchy
       +-src       Local source code
       No other directories, except those listed below, may be in /usr/local
       after first installing a FHS-compliant system.

       4.9.3  Specific Options

       If directories /lib<qual> or /usr/lib<qual> exist, the equivalent

       ____________________

       21.Host-specific  data  for  the  X  Window System must not be stored in
          /usr/lib/X11.  Host-specific configuration files such as  Xconfig  or
          XF86Config  must  be stored in /etc/X11.  This includes configuration
          data such as system.twmrc even if it is only made a symbolic link  to
          a more global configuration file (probably in /usr/X11R6/lib/X11).

       22.The  case  where  /usr/lib  and /usr/lib<qual> are the same (one is a
          symbolic link to the  other)  these  files  and  the  per-application
          subdirectories will exist.

       23.Software  placed  in  / or /usr may be overwritten by system upgrades
          (though we recommend that distributions do not overwrite data in /etc
          under these circumstances).  For this reason, local software must not
          be placed outside of /usr/local without good reason.

                                        - 22 -





       Filesystem Hierarchy Standard                               May 23, 2001



       directories must also exist in /usr/local.

       4.10  /usr/sbin : Non-essential standard system binaries

       4.10.1  Purpose

       This directory contains any non-essential binaries used exclusively by
       the system administrator.  System administration programs that are
       required for system repair, system recovery, mounting /usr, or other
       essential functions must be placed in /sbin instead.24

       4.11  /usr/share : Architecture-independent data

       4.11.1  Purpose

       The /usr/share hierarchy is for all read-only architecture independent
       data files.25

       This hierarchy is intended to be shareable among all architecture
       platforms of a given OS; thus, for example, a site with i386, Alpha, and
       PPC platforms might maintain a single /usr/share directory that is
       centrally-mounted.  Note, however, that /usr/share is generally not
       intended to be shared by different OSes or by different releases of the
       same OS.

       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.

       Game data stored in /usr/share/games must be purely static data.  Any
       modifiable files, such as score files, game play logs, and so forth,
       should be placed in /var/games.

       4.11.2  Requirements

       The following directories, or symbolic links to directories, must be in
       /usr/share
       /usr/share -- Architecture-independent data
       +-man       Online manuals
       +-misc      Miscellaneous architecture-independent data

       4.11.3  Specific Options

       The following directories, or symbolic links to directories, must be in
       /usr/share, if the corresponding subsystem is installed:


       ____________________

       24.Locally installed system administration programs should be placed  in
          /usr/local/sbin.

       25.Much of this data originally lived in /usr  (man,  doc)  or  /usr/lib
          (dict, terminfo, zoneinfo).

                                        - 23 -





       Filesystem Hierarchy Standard                               May 23, 2001



       /usr/share -- Architecture-independent data
       +-dict      Word lists (optional)
       +-doc       Miscellaneous documentation (optional)
       +-games     Static data files for /usr/games (optional)
       +-info      GNU Info system's primary directory (optional)
       +-locale    Locale information (optional)
       +-nls       Message catalogs for Native language support (optional)
       +-sgml      SGML and XML data (optional)
       +-terminfo  Directories for terminfo database (optional)
       +-tmac      troff macros not distributed with groff (optional)
       +-zoneinfo  Timezone information and configuration (optional)
       It is recommended that application-specific, architecture-independent
       directories be placed here.  Such directories include groff, perl,
       ghostscript, texmf, and kbd (Linux) or syscons (BSD).  They may,
       however, be placed in /usr/lib for backwards compatibility, at the
       distributor's discretion.  Similarly, a /usr/lib/games hierarchy may be
       used in addition to the /usr/share/games hierarchy if the distributor
       wishes to place some game data there.

       4.11.4  /usr/share/dict : Word lists (optional)

       4.11.4.1  Purpose

       This directory is the home for word lists on the system; Traditionally
       this directory contains only the English words file, which is used by
       look(1) and various spelling programs.  words may use either American or
       British spelling.

       BEGIN RATIONALE
       The reason that only word lists are located here is that they are the
       only files common to all spell checkers.

       END RATIONALE

       4.11.4.2  Specific Options

       The following files, or symbolic links to files, must be in
       /usr/share/dict, if the corresponding subsystem is installed:

       words   List of English words (optional)

       Sites that require both American and British spelling may link words to
       /usr/share/dict/american-english or /usr/share/dict/british-english.

       Word lists for other languages may be added using the English name for
       that language, e.g., /usr/share/dict/french, /usr/share/dict/danish,
       etc.  These should, if possible, use an ISO 8859 character set which is
       appropriate for the language in question; if possible the Latin1 (ISO
       8859-1) character set should be used (this is often not possible).

       Other word lists must be included here, if present.

       4.11.5  /usr/share/man : Manual pages



                                        - 24 -





       Filesystem Hierarchy Standard                               May 23, 2001



       4.11.5.1  Purpose

       This section details the organization for manual pages throughout the
       system, including /usr/share/man.  Also refer to the section on
       /var/cache/man.

       The primary <mandir> of the system is /usr/share/man.  /usr/share/man
       contains manual information for commands and data under the / and /usr
       filesystems.26

       Manual pages are stored in <mandir>/<locale>/man<section>/<arch>.  An
       explanation of <mandir>, <locale>, <section>, and <arch> is given below.

       A description of each section follows:

          o 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.

          o man2: System calls
            This section describes all of the system calls (requests for the
            kernel to perform operations).

          o 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.

          o 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.

          o 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.

          o man6: Games
            This chapter documents games, demos, and generally trivial
            programs.  Different people have various notions about how
            essential this is.

          o man7: Miscellaneous
            Manual pages that are difficult to classify are designated as being
            section 7.  The troff and other text processing macro packages are

       ____________________

       26.Obviously,  there  are  no  manual  pages  in  / because they are not
          required at boot time nor are they required in emergencies.27

       27.Really.

                                        - 25 -





       Filesystem Hierarchy Standard                               May 23, 2001



            found here.

          o 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.

       4.11.5.2  Specific Options

       The following directories, or symbolic links to directories, must be in
       /usr/share/<mandir>/<locale>, unless they are empty:28
       <mandir>/<locale> -- A manual page hierarchy
       +-man1      User programs (optional)
       +-man2      System calls (optional)
       +-man3      Library calls (optional)
       +-man4      Special files (optional)
       +-man5      File formats (optional)
       +-man6      Games (optional)
       +-man7      Miscellaneous (optional)
       +-man8      System administration (optional)
       The component <section> describes the manual section.

       Provisions must be made in the structure of /usr/share/man to support
       manual pages which are written in different (or multiple) languages.
       These provisions must take into account the storage and reference of
       these manual pages.  Relevant factors include language (including
       geographical-based differences), and character code set.

       This naming of language subdirectories of /usr/share/man is based on
       Appendix E of the POSIX 1003.1 standard which describes the locale
       identification string -- the most well-accepted method to describe a
       cultural environment.  The <locale> string is:

            <language>[_<territory>][.<character-set>][,<version>]

       The <language> field must be taken from ISO 639 (a code for the
       representation of names of languages).  It must be two characters wide
       and specified with lowercase letters only.

       The <territory> field must be the two-letter code of ISO 3166 (a
       specification of representations of countries), if possible.  (Most
       people are familiar with the two-letter codes used for the country codes
       in email addresses.29) It must be two characters wide and specified with
       uppercase letters only.

       The <character-set> field must represent the standard describing the
       character set.  If the <character-set> field is just a numeric

       ____________________

       28.For  example,  if  /usr/local/man  has  no  manual pages in section 4
          (Devices), then /usr/local/man/man4 may be omitted.

       29.A  major  exception to this rule is the United Kingdom, which is `GB'
          in the ISO 3166, but `UK' for most email addresses.

                                        - 26 -





       Filesystem Hierarchy Standard                               May 23, 2001



       specification, the number represents the number of the international
       standard describing the character set.  It is recommended that this be a
       numeric representation if possible (ISO standards, especially), not
       include additional punctuation symbols, and that any letters be in
       lowercase.

       A parameter specifying a <version> of the profile may be placed after
       the <character-set> field, delimited by a comma.  This may be used to
       discriminate between different cultural needs; for instance, dictionary
       order versus a more systems-oriented collating order.  This standard
       recommends not using the <version> field, unless it is necessary.

       Systems which use a unique language and code set for all manual pages
       may omit the <locale> substring and store all manual pages in <mandir>.
       For example, systems which only have English manual pages coded with
       ASCII, may store manual pages (the man<section> directories) directly in
       /usr/share/man.  (That is the traditional circumstance and arrangement,
       in fact.)

       Countries for which there is a well-accepted standard character code set
       may omit the <character-set> field, but it is strongly recommended that
       it be included, especially for countries with several competing
       standards.

       Various examples:

       Language   Territory        Character Set     Directory
       -------------------------------------------------------------------------
       English    --               ASCII             /usr/share/man/en
       English    United Kingdom   ASCII             /usr/share/man/en_GB
       English    United States    ASCII             /usr/share/man/en_US
       French     Canada           ISO 8859-1        /usr/share/man/fr_CA
       French     France           ISO 8859-1        /usr/share/man/fr_FR
       German     Germany          ISO 646           /usr/share/man/de_DE.646
       German     Germany          ISO 6937          /usr/share/man/de_DE.6937
       German     Germany          ISO 8859-1        /usr/share/man/de_DE.88591
       German     Switzerland      ISO 646           /usr/share/man/de_CH.646
       Japanese   Japan            JIS               /usr/share/man/ja_JP.jis
       Japanese   Japan            SJIS              /usr/share/man/ja_JP.sjis
       Japanese   Japan            UJIS (or EUC-J)   /usr/share/man/ja_JP.ujis

       Similarly, provision must be made for manual pages which are
       architecture-dependent, such as documentation on device-drivers or low-
       level system administration commands.  These must be placed under an
       <arch> directory in the appropriate man<section> directory; for example,
       a man page for the i386 ctrlaltdel(8) command might be placed in
       /usr/share/man/<locale>/man8/i386/ctrlaltdel.8.

       Manual pages for commands and data under /usr/local are stored in
       /usr/local/man.  Manual pages for X11R6 are stored in /usr/X11R6/man.
       It follows that all manual page hierarchies in the system must have the
       same structure as /usr/share/man.

       The cat page sections (cat<section>) containing formatted manual page


                                        - 27 -





       Filesystem Hierarchy Standard                               May 23, 2001



       entries are also found within subdirectories of <mandir>/<locale>, but
       are not required nor may they be distributed in lieu of nroff source
       manual pages.

       The numbered sections "1" through "8" are traditionally defined.  In
       general, the file name for manual pages located within a particular
       section end with .<section>.

       In addition, some large sets of application-specific manual pages have
       an additional suffix appended to the manual page filename.  For example,
       the MH mail handling system manual pages must have mh appended to all MH
       manuals.  All X Window System manual pages must have an x appended to
       the filename.

       The practice of placing various language manual pages in appropriate
       subdirectories of /usr/share/man also applies to the other manual page
       hierarchies, such as /usr/local/man and /usr/X11R6/man.  (This portion
       of the standard also applies later in the section on the optional
       /var/cache/man structure.)

       4.11.6  /usr/share/misc : Miscellaneous architecture-independent data

       This directory contains miscellaneous architecture-independent files
       which don't require a separate subdirectory under /usr/share.

       4.11.6.1  Specific Options

       The following files, or symbolic links to files, must be in
       /usr/share/misc, if the corresponding subsystem is installed:

       ascii        ASCII character set table (optional)
       magic        Default list of magic numbers for the file command (optional)
       termcap      Terminal capability database (optional)
       termcap.db   Terminal capability database (optional)

       Other (application-specific) files may appear here,30 but a distributor
       may place them in /usr/lib at their discretion.

       4.11.7  /usr/share/sgml : SGML and XML data (optional)

       4.11.7.1  Purpose

       /usr/share/sgml contains architecture-independent files used by SGML or
       XML applications, such as ordinary catalogs (not the centralized ones,
       see /etc/sgml), DTDs, entities, or style sheets.

       ____________________

       30.Some such files include:

          { airport,  birthtoken,  eqnchar,  getopt,  gprof.callg,  gprof.flat,
            inter.phone,   ipfw.samp.filters,  ipfw.samp.scripts,  keycap.pcvt,
            mail.help, mail.tildehelp,  man.template,  map3270,  mdoc.template,
            more.help,    na.phone,    nslookup.help,   operator,   scsi_modes,
            sendmail.hf, style, units.lib, vgrindefs, vgrindefs.db, zipcodes }

                                        - 28 -





       Filesystem Hierarchy Standard                               May 23, 2001



       4.11.7.2  Specific Options

       The following directories, or symbolic links to directories, must be in
       /usr/share/sgml, if the corresponding subsystem is installed:
       /usr/share/sgml -- SGML and XML data
       +-docbook   docbook DTD (optional)
       +-tei       tei DTD (optional)
       +-html      html DTD (optional)
       +-mathml    mathml DTD (optional)
       Other files that are not specific to a given DTD may reside in their own
       subdirectory.

       4.12  /usr/src : Source code (optional)

       4.12.1  Purpose

       Any non-local source code should be placed in this subdirectory.







































                                        - 29 -





       Filesystem Hierarchy Standard                               May 23, 2001



       5.  The /var Hierarchy

       5.1  Purpose

       /var contains variable data files.  This includes spool directories and
       files, administrative and logging data, 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.

       /var is specified here in order to make it possible to mount /usr read-
       only.  Everything that once went into /usr that is written to during
       system operation (as opposed to installation and software maintenance)
       must be in /var.

       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.

       5.2  Requirements

       The following directories, or symbolic links to directories, are
       required in /var.
       /var -- Variable data
       +-cache     Application cache data
       +-lib       Variable state information
       +-local     Variable data for /usr/local
       +-lock      Lock files
       +-log       Log files and directories
       +-opt       Variable data for /opt
       +-run       Data relevant to running processes
       +-spool     Application spool data
       +-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

       5.3  Specific Options



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       Filesystem Hierarchy Standard                               May 23, 2001



       The following directories, or symbolic links to directories, must be in
       /var, if the corresponding subsystem is installed:
       /var -- Variable data
       +-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)

       5.4  /var/account : Process accounting logs (optional)

       5.4.1  Purpose

       This directory holds the current active process accounting log and the
       composite process usage data (as used in some UNIX-like systems by
       lastcomm and sa).

       5.5  /var/cache : Application cache data

       5.5.1  Purpose

       /var/cache is intended for cached data from applications.  Such data is
       locally generated as a result of time-consuming I/O or calculation.  The
       application must be able to regenerate or restore the data.  Unlike
       /var/spool, the cached files can be deleted without data loss.  The data
       must remain valid between invocations of the application and rebooting
       the system.

       Files located under /var/cache may be expired in an application specific
       manner, by the system administrator, or both.  The application must
       always be able to recover from manual deletion of these files (generally
       because of a disk space shortage).  No other requirements are made on
       the data format of the cache directories.

       BEGIN RATIONALE
       The existence of a separate directory for cached data allows system
       administrators to set different disk and backup policies from other
       directories in /var.

       END RATIONALE

       5.5.2  Specific Options

       /var/cache -- Cache directories
       +-fonts     Locally-generated fonts (optional)
       +-man       Locally-formatted manual pages (optional)
       +-www       WWW proxy or cache data (optional)
       +-<package> Package specific cache data (optional)
       5.5.3  /var/cache/fonts : Locally-generated fonts (optional)

       5.5.3.1  Purpose

       The directory /var/cache/fonts should be used to store any dynamically-
       created fonts.  In particular, all of the fonts which are automatically


                                        - 31 -





       Filesystem Hierarchy Standard                               May 23, 2001



       generated by mktexpk must be located in appropriately-named
       subdirectories of /var/cache/fonts.31

       5.5.3.2  Specific Options

       Other dynamically created fonts may also be placed in this tree, under
       appropriately-named subdirectories of /var/cache/fonts.

       5.5.4  /var/cache/man : Locally-formatted manual pages (optional)

       5.5.4.1  Purpose

       This directory provides a standard location for sites that provide a
       read-only /usr partition, but wish to allow caching of locally-formatted
       man pages.  Sites that mount /usr as writable (e.g., single-user
       installations) may choose not to use /var/cache/man and may write
       formatted man pages into the cat<section> directories in /usr/share/man
       directly.  We recommend that most sites use one of the following options
       instead:

          o Preformat all manual pages alongside the unformatted versions.

          o Allow no caching of formatted man pages, and require formatting to
            be done each time a man page is brought up.

          o Allow local caching of formatted man pages in /var/cache/man.

       The structure of /var/cache/man needs to reflect both the fact of
       multiple man page hierarchies and the possibility of multiple language
       support.

       Given an unformatted manual page that normally appears in
       <path>/man/<locale>/man<section>, the directory to place formatted man
       pages in is /var/cache/man/<catpath>/<locale>/cat<section>, where
       <catpath> is derived from <path> by removing any leading usr and/or
       trailing share pathname components.32 (Note that the <locale> component
       may be missing.)

       Man pages written to /var/cache/man may eventually be transferred to the
       appropriate preformatted directories in the source man hierarchy or
       expired; likewise formatted man pages in the source man hierarchy may be
       expired if they are not accessed for a period of time.

       If preformatted manual pages come with a system on read-only media (a

       ____________________

       31.This standard  does  not  currently  incorporate  the  TeX  Directory
          Structure  (a  document  that  describes  the  layout  TeX  files and
          directories), but it  may  be  useful  reading.   It  is  located  at
          ftp://ctan.tug.org/tex/.

       32.For   example,    /usr/share/man/man1/ls.1    is    formatted    into
          /var/cache/man/cat1/ls.1, and /usr/X11R6/man/<locale>/man3/XtClass.3x
          into /var/cache/man/X11R6/<locale>/cat3/XtClass.3x.

                                        - 32 -





       Filesystem Hierarchy Standard                               May 23, 2001



       CD-ROM, for instance), they must be installed in the source man
       hierarchy (e.g. /usr/share/man/cat<section>).  /var/cache/man is
       reserved as a writable cache for formatted manual pages.

       BEGIN RATIONALE
       Release 1.2 of the standard specified /var/catman for this hierarchy.
       The path has been moved under /var/cache to better reflect the dynamic
       nature of the formatted man pages.  The directory name has been changed
       to man to allow for enhancing the hierarchy to include post-processed
       formats other than "cat", such as PostScript, HTML, or DVI.

       END RATIONALE

       5.6  /var/crash : System crash dumps (optional)

       5.6.1  Purpose

       This directory holds system crash dumps.  As of the date of this release
       of the standard, system crash dumps were not supported under Linux.

       5.7  /var/games : Variable game data (optional)

       5.7.1  Purpose

       Any variable data relating to games in /usr should be placed here.
       /var/games should hold the variable data previously found in /usr;
       static data, such as help text, level descriptions, and so on, must
       remain elsewhere, such as /usr/share/games.

       BEGIN RATIONALE
       /var/games has been given a hierarchy of its own, rather than leaving it
       merged in with the old /var/lib as in release 1.2.  The separation
       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.

       END RATIONALE

       5.8  /var/lib : Variable state information

       5.8.1  Purpose

       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 must never 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.
       State information should generally remain valid after a reboot, should
       not be logging output, and should not be spooled data.

       An application (or a group of inter-related applications) must use a


                                        - 33 -





       Filesystem Hierarchy Standard                               May 23, 2001



       subdirectory of /var/lib for its data.33  There is one required
       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.

       5.8.2  Requirements

       The following directories, or symbolic links to directories, are
       required in /var/lib:
       /var/lib -- Variable state information
       +-misc      Miscellaneous state data

       5.8.3  Specific Options

       The following directories, or symbolic links to directories, must be in
       /var/lib, if the corresponding subsystem is installed:
       /var/lib -- Variable state information
       +-<editor>  Editor backup files and state (optional)
       +-<pkgtool> Packaging support files (optional)
       +-<package> State data for packages and subsystems (optional)
       +-hwclock   State directory for hwclock (optional)
       +-xdm       X display manager variable data (optional)

       5.8.4  /var/lib/<editor> : Editor backup files and state (optional)

       5.8.4.1  Purpose

       These directories contain saved files generated by any unexpected
       termination of an editor (e.g., elvis, jove, nvi).

       Other editors may not require a directory for crash-recovery files, but
       may require a well-defined place to store other information while the
       editor is running.  This information should be stored in a subdirectory
       under /var/lib (for example, GNU Emacs would place lock files in
       /var/lib/emacs/lock).

       Future editors may require additional state information beyond crash-
       recovery files and lock files -- this information should also be placed
       under /var/lib/<editor>.

       BEGIN RATIONALE
       Previous Linux releases, as well as all commercial vendors, use
       /var/preserve for vi or its clones.  However, each editor uses its own
       format for these crash-recovery files, so a separate directory is needed
       for each editor.

       ____________________

       33.An  important  difference  between  this version of this standard and
          previous ones  is  that  applications  are  now  required  to  use  a
          subdirectory of /var/lib.

                                        - 34 -





       Filesystem Hierarchy Standard                               May 23, 2001



       Editor-specific lock files are usually quite different from the device
       or resource lock files that are stored in /var/lock and, hence, are
       stored under /var/lib.

       END RATIONALE

       5.8.5  /var/lib/hwclock : State directory for hwclock (optional)

       5.8.5.1  Purpose

       This directory contains the file /var/lib/hwclock/adjtime.

       BEGIN RATIONALE
       In FHS 2.1, this file was /etc/adjtime, but as hwclock updates it, that
       was obviously incorrect.

       END RATIONALE

       5.8.6  /var/lib/misc : Miscellaneous variable data

       5.8.6.1  Purpose

       This directory contains variable data not placed in a subdirectory in
       /var/lib.  An attempt should be made to use relatively unique names in
       this directory to avoid namespace conflicts.34

       5.9  /var/lock : Lock files

       5.9.1  Purpose

       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.  For example, to lock
       /dev/ttyS0 the file "LCK..ttyS0" would be created.  35

       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.


       ____________________

       34.This  hierarchy should contain files stored in /var/db in current BSD
          releases.  These  include  locate.database  and  mountdtab,  and  the
          kernel symbol database(s).

       35.Then, anything wishing to use /dev/ttyS0 can read the lock  file  and
          act accordingly (all locks in /var/lock should be world-readable).

                                        - 35 -





       Filesystem Hierarchy Standard                               May 23, 2001



       5.10  /var/log : Log files and directories

       5.10.1  Purpose

       This directory contains miscellaneous log files.  Most logs must be
       written to this directory or an appropriate subdirectory.

       5.10.2  Specific Options

       The following files, or symbolic links to files, must be in /var/log, if
       the corresponding subsystem is installed:

       lastlog    record of last login of each user
       messages   system messages from syslogd
       wtmp       record of all logins and logouts

       5.11  /var/mail : User mailbox files (optional)

       5.11.1  Purpose

       The mail spool must be accessible through /var/mail and the mail spool
       files must take the form <username>.36

       User mailbox files in this location must be stored in the standard UNIX
       mailbox format.

       BEGIN RATIONALE
       The logical location for this directory was changed from /var/spool/mail
       in order to bring FHS in-line with nearly every UNIX implementation.
       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).

       It is important to note that there is no requirement to physically move
       the mail spool to this location.  However, programs and header files
       must be changed to use /var/mail.

       END RATIONALE

       5.12  /var/opt : Variable data for /opt

       5.12.1  Purpose

       Variable data of the packages in /opt must be installed in
       /var/opt/<package>, where <package> is the name of the subtree in /opt
       where the static data from an add-on software package is stored, except
       where superseded by another file in /etc.  No structure is imposed on
       the internal arrangement of /var/opt/<package>.




       ____________________

       36.Note that /var/mail may be a symbolic link to another directory.

                                        - 36 -





       Filesystem Hierarchy Standard                               May 23, 2001



       BEGIN RATIONALE
       Refer to the rationale for /opt.

       END RATIONALE

       5.13  /var/run : Run-time variable data

       5.13.1  Purpose

       This directory contains system information data describing the system
       since it was booted.  Files under this directory must be cleared
       (removed or truncated as appropriate) at the beginning of the boot
       process.  Programs may have a subdirectory of /var/run; this is
       encouraged for programs that use more than one run-time file.37 Process
       identifier (PID) files, which were originally placed in /etc, must be
       placed in /var/run.  The naming convention for PID files is <program-
       name>.pid.  For example, the crond PID file is named /var/run/crond.pid.

       5.13.2  Requirements

       The internal format of PID files remains unchanged.  The file must
       consist of the process identifier in ASCII-encoded decimal, followed by
       a newline character.  For example, if crond was process number 25,
       /var/run/crond.pid would contain three characters: two, five, and
       newline.

       Programs that read PID files should be somewhat flexible in what they
       accept; i.e., they should ignore extra whitespace, leading zeroes,
       absence of the trailing newline, or additional lines in the PID file.
       Programs that create PID files should use the simple specification
       located in the above paragraph.

       The utmp file, which stores information about who is currently using the
       system, is located in this directory.

       Programs that maintain transient UNIX-domain sockets must place them in
       this directory.

       5.14  /var/spool : Application spool data

       5.14.1  Purpose

       /var/spool contains data which is awaiting some kind of later
       processing.  Data in /var/spool represents work to be done in the future
       (by a program, user, or administrator); often data is deleted after it
       has been processed.38

       ____________________

       37./var/run should be unwritable for unprivileged users (root  or  users
          running  daemons);  it  is  a  major security problem if any user can
          write in this directory.

       38.UUCP  lock  files must be placed in /var/lock.  See the above section
          on /var/lock.

                                        - 37 -





       Filesystem Hierarchy Standard                               May 23, 2001



       5.14.2  Specific Options

       The following directories, or symbolic links to directories, must be in
       /var/spool, if the corresponding subsystem is installed:
       /var/spool -- Spool directories
       +-lpd       Printer spool directory (optional)
       +-mqueue    Outgoing mail queue (optional)
       +-news      News spool directory (optional)
       +-rwho      Rwhod files (optional)
       +-uucp      Spool directory for UUCP (optional)
       5.14.3  /var/spool/lpd : Line-printer daemon print queues (optional)

       5.14.3.1  Purpose

       The lock file for lpd, lpd.lock, must be placed in /var/spool/lpd.  It
       is suggested that the lock file for each printer be placed in the spool
       directory for that specific printer and named lock.

       5.14.3.2  Specific Options

       /var/spool/lpd -- Printer spool directory
       +-<printer> Spools for a specific printer (optional)

       5.14.4  /var/spool/rwho : Rwhod files (optional)

       5.14.4.1  Purpose

       This directory holds the rwhod information for other systems on the
       local net.

       BEGIN RATIONALE
       Some BSD releases use /var/rwho for this data; given its historical
       location in /var/spool on other systems and its approximate fit to the
       definition of `spooled' data, this location was deemed more appropriate.

       END RATIONALE

       5.15  /var/tmp : Temporary files preserved between system reboots

       5.15.1  Purpose

       The /var/tmp directory is made available for programs that require
       temporary files or directories that are preserved between system
       reboots.  Therefore, data stored in /var/tmp is more persistent than
       data in /tmp.

       Files and directories located in /var/tmp must not be deleted when the
       system is booted.  Although data stored in /var/tmp is typically deleted
       in a site-specific manner, it is recommended that deletions occur at a
       less frequent interval than /tmp.

       5.16  /var/yp : Network Information Service (NIS) database files
       (optional)



                                        - 38 -





       Filesystem Hierarchy Standard                               May 23, 2001



       5.16.1  Purpose

       Variable data for the Network Information Service (NIS), formerly known
       as the Sun Yellow Pages (YP), must be placed in this directory.

       BEGIN RATIONALE
       /var/yp is the standard directory for NIS (YP) data and is almost
       exclusively used in NIS documentation and systems.39

       END RATIONALE









































       ____________________

       39.NIS  should  not  be  confused  with Sun NIS+, which uses a different
          directory, /var/nis.

                                        - 39 -





       Filesystem Hierarchy Standard                               May 23, 2001



       6.  Operating System Specific Annex

       This section is for additional requirements and recommendations that
       only apply to a specific operating system.  The material in this section
       should never conflict with the base standard.

       6.1  Linux

       This is the annex for the Linux operating system.

       6.1.1  / : Root directory

       On Linux systems, if the kernel is located in /, we recommend using the
       names vmlinux or vmlinuz, which have been used in recent Linux kernel
       source packages.

       6.1.2  /bin : Essential user command binaries (for use by all users)

       Linux systems which require them place these additional files into /bin.

       { setserial }

       6.1.3  /dev : Devices and special files

       All devices and special files in /dev should adhere to the Linux
       Allocated Devices document, which is available with the Linux kernel
       source.  It is maintained by H. Peter Anvin <hpa@zytor.com>.

       Symbolic links in /dev should not be distributed with Linux systems
       except as provided in the Linux Allocated Devices document.

       BEGIN RATIONALE
       The requirement not to make symlinks promiscuously is made because local
       setups will often differ from that on the distributor's development
       machine.  Also, if a distribution install script configures the symbolic
       links at install time, these symlinks will often not get updated if
       local changes are made in hardware.  When used responsibly at a local
       level, however, they can be put to good use.

       END RATIONALE

       6.1.4  /etc : Host-specific system configuration

       Linux systems which require them place these additional files into /etc.

       { lilo.conf }



       6.1.5  /proc : Kernel and process information virtual filesystem

       The proc filesystem is the de-facto standard Linux method for handling
       process and system information, rather than /dev/kmem and other similar
       methods.  We strongly encourage this for the storage and retrieval of


                                        - 40 -





       Filesystem Hierarchy Standard                               May 23, 2001



       process information as well as other kernel and memory information.

       6.1.6  /sbin : Essential system binaries

       Linux systems place these additional files into /sbin.

          o Second extended filesystem commands (optional):

            { badblocks, dumpe2fs, e2fsck, mke2fs, mklost+found, tune2fs }

          o Boot-loader map installer (optional):

            { lilo }

       Optional files for /sbin:

          o Static binaries:

            { ldconfig, sln, ssync }

            Static ln (sln) and static sync (ssync) are useful when things go
            wrong.  The primary use of sln (to repair incorrect symlinks in
            /lib after a poorly orchestrated upgrade) is no longer a major
            concern now that the ldconfig program (usually located in
            /usr/sbin) exists and can act as a guiding hand in upgrading the
            dynamic libraries.  Static sync is useful in some emergency
            situations.  Note that these need not be statically linked versions
            of the standard ln and sync, but may be.

            The ldconfig binary is optional for /sbin since a site may choose
            to run ldconfig at boot time, rather than only when upgrading the
            shared libraries.  (It's not clear whether or not it is
            advantageous to run ldconfig on each boot.)  Even so, some people
            like ldconfig around for the following (all too common) situation:

                (1) I've just removed /lib/<file>.

                (2) I can't find out the name of the library because ls is
                    dynamically linked, I'm using a shell that doesn't have ls
                    built-in, and I don't know about using "echo *" as a
                    replacement.

                (3) I have a static sln, but I don't know what to call the
                    link.

          o Miscellaneous:

            { ctrlaltdel, kbdrate }

            So as to cope with the fact that some keyboards come up with such a
            high repeat rate as to be unusable, kbdrate may be installed in
            /sbin on some systems.

            Since the default action in the kernel for the Ctrl-Alt-Del key


                                        - 41 -





       Filesystem Hierarchy Standard                               May 23, 2001



            combination is an instant hard reboot, it is generally advisable to
            disable the behavior before mounting the root filesystem in read-
            write mode.  Some init suites are able to disable Ctrl-Alt-Del, but
            others may require the ctrlaltdel program, which may be installed
            in /sbin on those systems.

       6.1.7  /usr/include : Header files included by C programs

       These symbolic links are required if a C or C++ compiler is installed
       and only for systems not based on glibc.

           /usr/include/asm -> /usr/src/linux/include/asm-<arch>
           /usr/include/linux -> /usr/src/linux/include/linux

       6.1.8  /usr/src : Source code

       For systems based on glibc, there are no specific guidelines for this
       directory.  For systems based on Linux libc revisions prior to glibc,
       the following guidelines and rationale apply:

       The only source code that should be placed in a specific location is the
       Linux kernel source code.  It is located in /usr/src/linux.

       If a C or C++ compiler is installed, but the complete Linux kernel
       source code is not installed, then the include files from the kernel
       source code must be located in these directories:

           /usr/src/linux/include/asm-<arch>
           /usr/src/linux/include/linux

       <arch> is the name of the system architecture.

       Note: /usr/src/linux may be a symbolic link to a kernel source code
       tree.

       BEGIN RATIONALE
       It is important that the kernel include files be located in
       /usr/src/linux and not in /usr/include so there are no problems when
       system administrators upgrade their kernel version for the first time.

       END RATIONALE

       6.1.9  /var/spool/cron : cron and at jobs

       This directory contains the variable data for the cron and at programs.











                                        - 42 -





       Filesystem Hierarchy Standard                               May 23, 2001



       7.  Appendix

       7.1  The FHS mailing list

       The FHS mailing list is located at <fhs-discuss@ucsd.edu>.  To subscribe
       to the list send mail to <listserv@ucsd.edu> with body "ADD fhs-
       discuss".

       Thanks to Network Operations at the University of California at San
       Diego who allowed us to use their excellent mailing list server.

       As noted in the introduction, please do not send mail to the mailing
       list without first contacting the FHS editor or a listed contributor.

       7.2  Background of the FHS

       The process of developing a standard filesystem hierarchy began in
       August 1993 with an effort to restructure the file and directory
       structure of Linux.  The FSSTND, a filesystem hierarchy standard
       specific to the Linux operating system, was released on February 14,
       1994.  Subsequent revisions were released on October 9, 1994 and March
       28, 1995.

       In early 1995, the goal of developing a more comprehensive version of
       FSSTND to address not only Linux, but other UNIX-like systems was
       adopted with the help of members of the BSD development community.  As a
       result, a concerted effort was made to focus on issues that were general
       to UNIX-like systems.  In recognition of this widening of scope, the
       name of the standard was changed to Filesystem Hierarchy Standard or FHS
       for short.

       Volunteers who have contributed extensively to this standard are listed
       at the end of this document.  This standard represents a consensus view
       of those and other contributors.

       7.3  General Guidelines

       Here are some of the guidelines that have been used in the development
       of this standard:

          o Solve technical problems while limiting transitional difficulties.

          o Make the specification reasonably stable.

          o Gain the approval of distributors, developers, and other decision-
            makers in relevant development groups and encourage their
            participation.

          o Provide a standard that is attractive to the implementors of
            different UNIX-like systems.

       7.4  Scope

       This document specifies a standard filesystem hierarchy for FHS


                                        - 43 -





       Filesystem Hierarchy Standard                               May 23, 2001



       filesystems by specifying the location of files and directories, and the
       contents of some system files.

       This standard has been designed to be used by system integrators,
       package developers, and system administrators in the construction and
       maintenance of FHS compliant filesystems.  It is primarily intended to
       be a reference and is not a tutorial on how to manage a conforming
       filesystem hierarchy.

       The FHS grew out of earlier work on FSSTND, a filesystem organization
       standard for the Linux operating system.  It builds on FSSTND to address
       interoperability issues not just in the Linux community but in a wider
       arena including 4.4BSD-based operating systems.  It incorporates lessons
       learned in the BSD world and elsewhere about multi-architecture support
       and the demands of heterogeneous networking.

       Although this standard is more comprehensive than previous attempts at
       filesystem hierarchy standardization, periodic updates may become
       necessary as requirements change in relation to emerging technology.  It
       is also possible that better solutions to the problems addressed here
       will be discovered so that our solutions will no longer be the best
       possible solutions.  Supplementary drafts may be released in addition to
       periodic updates to this document.  However, a specific goal is
       backwards compatibility from one release of this document to the next.

       Comments related to this standard are welcome.  Any comments or
       suggestions for changes may be directed to the FHS editor (Daniel
       Quinlan <quinlan@pathname.com>) or the FHS mailing list.  Typographical
       or grammatical comments should be directed to the FHS editor.

       Before sending mail to the mailing list it is requested that you first
       contact the FHS editor in order to avoid excessive re-discussion of old
       topics.

       Questions about how to interpret items in this document may occasionally
       arise.  If you have need for a clarification, please contact the FHS
       editor.  Since this standard represents a consensus of many
       participants, it is important to make certain that any interpretation
       also represents their collective opinion.  For this reason it may not be
       possible to provide an immediate response unless the inquiry has been
       the subject of previous discussion.

       7.5  Acknowledgments

       The developers of the FHS wish to thank the developers, system
       administrators, and users whose input was essential to this standard.
       We wish to thank each of the contributors who helped to write, compile,
       and compose this standard.

       The FHS Group also wishes to thank those Linux developers who supported
       the FSSTND, the predecessor to this standard.  If they hadn't
       demonstrated that the FSSTND was beneficial, the FHS could never have
       evolved.



                                        - 44 -





       Filesystem Hierarchy Standard                               May 23, 2001



       7.6  Contributors

       Brandon S. Allbery   <bsa@kf8nh.wariat.org>
       Keith Bostic         <bostic@cs.berkeley.edu>
       Drew Eckhardt        <drew@colorado.edu>
       Rik Faith            <faith@cs.unc.edu>
       Stephen Harris       <sweh@spuddy.mew.co.uk>
       Ian Jackson          <ijackson@cus.cam.ac.uk>
       John A. Martin       <jmartin@acm.org>
       Ian McCloghrie       <ian@ucsd.edu>
       Chris Metcalf        <metcalf@lcs.mit.edu>
       Ian Murdock          <imurdock@debian.org>
       David C. Niemi       <niemidc@clark.net>
       Daniel Quinlan       <quinlan@pathname.com>
       Eric S. Raymond      <esr@thyrsus.com>
       Rusty Russell        <rusty@rustcorp.com.au>
       Mike Sangrey         <mike@sojurn.lns.pa.us>
       David H. Silber      <dhs@glowworm.firefly.com>
       Thomas Sippel-Dau    <t.sippel-dau@ic.ac.uk>
       Theodore Ts'o        <tytso@athena.mit.edu>
       Stephen Tweedie      <sct@dcs.ed.ac.uk>
       Fred N. van Kempen   <waltje@infomagic.com>
       Bernd Warken         <bwarken@mayn.de>

































                                        - 45 -









                                       CONTENTS



       1.  Introduction ..................................................... 2
           1.1   Purpose .................................................... 2
           1.2   Conventions ................................................ 2

       2.  The Filesystem ................................................... 3

       3.  The Root Filesystem .............................................. 5
           3.1   Purpose .................................................... 5
           3.2   Requirements ............................................... 6
           3.3   Specific Options ........................................... 6
           3.4   /bin : Essential user command binaries (for use by all
                 users) ..................................................... 6
           3.5   /boot : Static files of the boot loader .................... 8
           3.6   /dev : Device files ........................................ 9
           3.7   /etc : Host-specific system configuration .................. 9
           3.8   /home : User home directories (optional) .................. 12
           3.9   /lib : Essential shared libraries and kernel modules ...... 12
           3.10  /lib<qual> : Alternate format essential shared libraries
                 (optional) ................................................ 13
           3.11  /mnt : Mount point for a temporarily mounted filesystem ... 13
           3.12  /opt : Add-on application software packages ............... 13
           3.13  /root : Home directory for the root user (optional) ....... 15
           3.14  /sbin : System binaries ................................... 15
           3.15  /tmp : Temporary files .................................... 16

       4.  The /usr Hierarchy .............................................. 18
           4.1   Purpose ................................................... 18
           4.2   Requirements .............................................. 18
           4.3   Specific Options .......................................... 18
           4.4   /usr/X11R6 : X Window System, Version 11 Release 6
                 (optional) ................................................ 18
           4.5   /usr/bin : Most user commands ............................. 19
           4.6   /usr/include : Directory for standard include files. ...... 20
           4.7   /usr/lib : Libraries for programming and packages ......... 20
           4.8   /usr/lib<qual> : Alternate format libraries (optional) .... 20
           4.9   /usr/local : Local hierarchy .............................. 21
           4.10  /usr/sbin : Non-essential standard system binaries ........ 22
           4.11  /usr/share : Architecture-independent data ................ 22
           4.12  /usr/src : Source code (optional) ......................... 28

       5.  The /var Hierarchy .............................................. 29
           5.1   Purpose ................................................... 29
           5.2   Requirements .............................................. 29
           5.3   Specific Options .......................................... 29
           5.4   /var/account : Process accounting logs (optional) ......... 30
           5.5   /var/cache : Application cache data ....................... 30
           5.6   /var/crash : System crash dumps (optional) ................ 32
           5.7   /var/games : Variable game data (optional) ................ 32
           5.8   /var/lib : Variable state information ..................... 32



                                           i









           5.9   /var/lock : Lock files .................................... 34
           5.10  /var/log : Log files and directories ...................... 35
           5.11  /var/mail : User mailbox files (optional) ................. 35
           5.12  /var/opt : Variable data for /opt ......................... 35
           5.13  /var/run : Run-time variable data ......................... 36
           5.14  /var/spool : Application spool data ....................... 36
           5.15  /var/tmp : Temporary files preserved between system
                 reboots ................................................... 37
           5.16  /var/yp : Network Information Service (NIS) database files
                 (optional) ................................................ 37

       6.  Operating System Specific Annex ................................. 39
           6.1   Linux ..................................................... 39

       7.  Appendix ........................................................ 42
           7.1   The FHS mailing list ...................................... 42
           7.2   Background of the FHS ..................................... 42
           7.3   General Guidelines ........................................ 42
           7.4   Scope ..................................................... 42
           7.5   Acknowledgments ........................................... 43
           7.6   Contributors .............................................. 44



































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