









              Filesystem Hierarchy Standard -- Version 2.0

                  Filesystem Hierarchy Standard Group
                        edited by 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.


October 26, 1997










































Filesystem Hierarchy Standard                           October 26, 1997



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, 1995, 1996, 1997 Daniel Quinlan

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  Status of the Standard

This is version 2.0 of the Filesystem Hierarchy Standard (FHS 2.0).

Comments on this standard are welcome from interested parties.
Suggestions for changes should be in the form of a proposed change of
text, together with appropriate supporting comments.

The guidelines in this standard are subject to modification.  Use of
information contained in this document is at your own risk.


1.2  Organization of the Standard

This standard is divided into these sections:

  1.  Introduction

  2.  The Filesystem: a statement of some guiding principles.

  3.  The Root Directory.

  4.  The /usr Hierarchy.

  5.  The /var Hierarchy.

  6.  Operating System Specific Annex.


1.3  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
file existed which could be either be found 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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1.4  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.


1.5  Scope

This document specifies a standard filesystem hierarchy for FHS
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 or 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 should be directed to the FHS editor (Daniel
Quinlan <quinlan@pathname.com>), or if you prefer, the FHS mailing list.
Typographical or grammatical comments should be directed to the FHS


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editor.

It is requested that you first contact the FHS editor before sending
mail to the mailing list in order to avoid excessive re-discussion of
old topics.  Improper messages will not be well-received on the mailing
list.

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.


1.6  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.


1.7  Intended Audience

The intended audience of this standard includes, but is not limited to
the following groups of people:

   o System Developers

   o System Integrators and Distributors

   o Application Developers

   o Documentation Writers

   o System Administrators and other interested parties (for information
     purposes)


1.8  Conformance with this Document

This section defines the meanings of the terms "compliant" and
"compatible" with respect to this standard, and of "partial" compliance


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and conformance.

An "implementation" here refers to a distribution, an installed system,
a program, a package (or some similar piece of software or data), or
some component thereof.

An implementation is fully compliant with this standard if every
requirement in this standard is met.  Every file or directory which is
part of the implementation must be located as specified in this
document.  If the contents of a file are described here the actual
contents must correspond to the description.  The implementation must
also attempt to find any files or directories (external to itself)
primarily or exclusively in the location specified in this standard.

An implementation is fully compatible with this standard if every file
or directory which it contains can be found by looking in the location
specified here and will be found with the contents as specified here,
even if that is not the primary or physical location of the file or
directory in question.  The implementation must, when it attempts to
find any files or directories which are not part of it, do so in the
location specified in this standard, though it may also attempt to find
it in other (non-standard) locations.

An implementation is partially compliant or compatible if it complies
with or is compatible with a significant subset of this document.
Partial compliance or compatibility is only intended to apply to
distributions and not to separate programs.  The phrase "a significant
subset" is admittedly subjective, and in borderline cases, the concerned
party should contact the FHS editor.  It is anticipated that some
variation will be tolerated in borderline cases.

To qualify as partially FHS compliant or partially FHS compatible an
implementation must provide a list of all places at which it and the FHS
document differ in addition to a brief explanation of the reasoning for
this difference.  This list shall be provided with the implementation in
question, and also made available to the FHS mailing list or the FHS
editor.

The terms "must", "should", "contains", "is" and so forth should be read
as requirements for compliance or compatibility.

Note that an implementation does not need to contain all the files and
directories specified in this standard to be compliant or compatible.
It is merely necessary for those files that it does contain to be
located appropriately.  For example, if the minix filesystem is not
supported by a distribution, the minix tools need not be included, even
though they are mentioned explicitly in the section on /sbin.

Furthermore, certain portions of this document are optional.  In this
case this will be stated explicitly, or indicated with the use of one or
more of "may", "recommend", or "suggest".  Items marked as optional have
no bearing on the compliance or conformance of an implementation; they
are suggestions meant to encourage common practice, but may be located
anywhere at the implementor's choice.


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2.  The Filesystem

The UNIX filesystem is characterized by:

   o A hierarchical structure

   o Consistent treatment of file data

   o Protection of file data

This standard assumes that the operating system underlying an FHS-
compliant file system supports the same basic security features found in
most UNIX filesystems.  Note that this standard does not attempt to
agree in every possible respect with any particular UNIX system's
implementation.  However, many aspects of this standard are based on
ideas found in UNIX and other UNIX-like systems.

This is after careful consideration of other factors, including:

   o Traditional and well-considered practices in UNIX-like systems.

   o The implementation of other filesystem structures

   o Applicable standards

It is possible to define two orthogonal categories of files: shareable
vs. unshareable and variable vs. static.

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.

For ease of backup, administration, and file-sharing on heterogenous
networks of systems, it is desirable that there be a simple and easily
understandable mapping from directories (especially directories
considered as potential mount points) to the type of data they contain.

Throughout this document, and in any well-planned filesystem, an
understanding of this basic principle will help guide the structure and
lend it additional consistency.

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.



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   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 can be considered a read-only filesystem shared
     with other FHS-compliant systems, using the postal mail system as a
     "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.

   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.  Since this chart contains generalized
examples, it may not apply to every possible implementation of an FHS-
compliant system.

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











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3.  The Root Directory

This section describes the root directory structure.  The contents of
the root filesystem should 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
     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 should be present on the root filesystem.

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

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 has many system-specific configuration files in
     it.  Possible examples include a kernel that is specific to the
     system, a different hostname, etc.  This means that the root
     filesystem isn't always shareable between networked systems.
     Keeping it small on networked systems minimizes the amount of space
     lost on servers to 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 should 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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BEGIN RATIONALE

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
/ -- the root directory
|
+-bin       Essential command binaries
+-boot      Static files of the boot loader
+-dev       Device files
+-etc       Host-specific system configuration
+-home      User home directories
+-lib       Essential shared libraries and kernel modules
+-mnt       Mount point of temporary partitions
+-opt       Add-on application software packages
+-root      Home directory for the root user
+-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.

The operating system kernel image should be located in either / or
/boot.  Additional information on kernel placement can be found in the
section regarding /boot, below.


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

/bin contains commands that may be used by both the system administrator
and by users, but which are required in single user mode.  It may also
contain commands which are used indirectly by scripts.

There should be no subdirectories within /bin.

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




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Required files for /bin:

   o General commands:

     The following commands have been included because they are
     essential.  A few are present because of their traditional
     placement in /bin.

     { cat, chgrp, chmod, chown, cp, date, dd, df, dmesg, echo, ed,
       false, kill, ln, login, ls, mkdir, mknod, more, mount, mv, ps,
       pwd, rm, rmdir, sed, setserial, sh, stty, su, sync, true, umount,
       uname }

     If /bin/sh is Bash, then /bin/sh should be a symbolic or hard link
     to /bin/bash since Bash behaves differently when called as sh or
     bash.  pdksh, which may be the /bin/sh on install disks, should
     likewise be arranged with /bin/sh being a symlink to /bin/ksh.  The
     use of a symbolic link in these cases allows users to easily see
     that /bin/sh is not a true Bourne shell.

     Since the de-facto standard location of the C-shell is /bin/csh, if
     and only if a C-shell or equivalent (such as tcsh) is available on
     the system, it should be available by the name /bin/csh.  /bin/csh
     may be a symbolic link to /bin/tcsh or /usr/bin/tcsh.

     Note: The [ and test commands are built into most commonly used
     Bourne shell (/bin/sh) replacements.  These two commands do not
     have to be placed in /bin; they may be placed in /usr/bin.  They
     must be included as separate binaries with any UNIX or UNIX-like
     system attempting to comply with the POSIX.2 standard.


   o Restoration commands:

     These commands have been added to make restoration of a system
     possible (provided that / is intact).

     { tar, gzip, gunzip (link to gzip), zcat (link to gzip) }

     If system backups are made using programs other than gzip and tar,
     then the root partition should contain the minimal necessary
     restoration components.  For instance, many systems should include
     cpio as it is the next most commonly used backup utility after tar.
     Conversely, if no restoration from the root partition is ever
     expected, then these binaries may be omitted (i.e., 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) should be available
     on the root partition.

     Restoration commands may appear in either /bin or /usr/bin on
     different systems.




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   o Networking commands:

     These are the only necessary networking binaries that both root and
     users will want or need to execute other than the ones in /usr/bin
     or /usr/local/bin.

     { domainname, hostname, netstat, ping }


3.2  /boot : Static files of the boot loader

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

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

Note: 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.


3.3  /dev : Device files

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

If it is possible that devices in /dev will need to be manually created,
/dev shall 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 should have provisions for creating any device that
may be found on the system, not just those that a particular
implementation installs.


3.4  /etc : Host-specific system configuration

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

No binaries should be located under /etc.

/etc -- Host-specific system configuration
|
+-X11       Configuration for the X Window System
+-opt       Configuration for /opt


The following section is intended partly to illuminate the description
of the contents of /etc with a number of examples; it is definitely not


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an exhaustive list.


Required files for /etc:

   o General files:

     { adjtime, csh.login, disktab, fdprm, fstab, gettydefs, group,
       inittab, confissue, ld.so.conf, lilo.conf, motd, mtab, mtools,
       passwd, profile, securetty, shells, syslog.conf, ttytype }


   o Networking files:

     { exports, ftpusers, gateways, host.conf, hosts, hosts.allow,
       hosts.deny, hosts.equiv, hosts.lpd, inetd.conf, networks,
       printcap, protocols, resolv.conf, rpc, services }

Notes:

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

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).


3.4.1  /etc/X11 : Configuration for the X Window System

/etc/X11 is the recommended location for all X11 host-specific
configuration.  This directory is necessary to allow local control if
/usr is mounted read only.  Files that should be in this directory
include Xconfig (and/or XF86Config) and Xmodmap.

Subdirectories of /etc/X11 may include those for xdm and for any other
programs (some window managers, for example) that need them.  We
recommend that window managers with only one configuration file which is
a default .*wmrc file should name it system.*wmrc (unless there is a
widely-accepted alternative name) and not use a subdirectory.  Any
window manager subdirectories should be identically named to the actual
window manager binary.

/etc/X11/xdm holds the configuration files for xdm.  These are most of
the files normally found in /usr/lib/X11/xdm.  Some local variable data
for xdm is stored in /var/state/xdm.


3.4.2  /etc/opt : Configuration files for /opt

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


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from that package is stored.  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

3.5  /home : User home directories (optional)

/home is a fairly standard concept, but it is clearly a site-specific
filesystem.  The setup will differ from host to host.  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.

Different people prefer to place user accounts in a variety of places.
Therefore, no program should rely on this location.  If you want to find
out a user's home directory, you should use the getpwent(3) library
function rather than relying on /etc/passwd because user information may
be stored remotely using systems such as NIS.


3.6  /lib : Essential shared libraries and kernel modules


The /lib directory contains those shared library images needed to boot
the system and run the commands in the root filesystem.

/lib -- essential shared libraries and kernel modules
|
+-modules   Loadable kernel modules


This includes /lib/libc.so.*, /lib/libm.so.*, the shared dynamic linker
/lib/ld.so, and other shared libraries required by binaries in /bin and
/sbin.

Shared libraries that are only necessary for binaries in /usr (such as


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any X Window binaries) do not belong in /lib. Only the shared libraries
required to run binaries in /bin and /sbin should be here.  The library
libm.so.* may also be placed in /usr/lib if it is not required by
anything in /bin or /sbin.

For compatibility reasons, /lib/cpp needs to exist as a reference to the
C preprocessor installed on the system.  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.)

The specification for /lib/modules is forthcoming.


3.7  /mnt : Mount point for temporarily mounted filesystems

This directory is provided so that the system administrator may
temporarily mount filesystems as needed.  The content of this directory
is a local issue and should not affect the manner in which any program
is run.

We recommend against the use of this directory by installation programs,
and suggest that a suitable temporary directory not in use by the system
should be used instead.


3.8  /opt : Add-on application software packages

/opt -- Add-on application software packages
|
+-<package> Static package objects


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

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

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

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 shall function normally in the absence of these reserved
directories.

Package files that are variable (change in normal operation) should be


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installed in /var/opt.  See the section on /var/opt for more
information.

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

No other package files should 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.


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 should 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.

END RATIONALE

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

/ is traditionally the home directory of the root account on UNIX
systems.  /root is used on many Linux systems and on some UNIX systems
(in order to reduce clutter in the / directory).  The root account's
home directory may be determined by developer or local preference.
Obvious possibilities include /, /root, and /home/root.

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.

Note: we recommend against using the root account for mundane things
such as mail and news, and that it be used solely for system
administration.  For this reason, we recommend that subdirectories such
as Mail and News 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.


3.10  /sbin : System binaries (binaries once kept in /etc)

Utilities used for system administration (and other root-only commands)
are stored in /sbin, /usr/sbin, and /usr/local/sbin.  /sbin typically


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contains binaries essential for booting the system in addition to the
binaries in /bin.  Anything executed after /usr is known to be mounted
(when there are no problems) should be placed into /usr/sbin.  Local-
only system administration binaries should be placed into
/usr/local/sbin.

Deciding what things go into "sbin" directories is simple: If a normal
(not a system administrator) user will ever run it directly, then it
should be placed in one of the "bin" directories.  Ordinary users should
not have to place any of the sbin directories in their path.

Note: For example, files such as chfn which users only occasionally use
should still be placed in /usr/bin.  ping, although it is absolutely
necessary for root (network recovery and diagnosis) is often used by
users and should 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.


Required files for /sbin:

   o General commands:

     { clock, getty, init, update, mkswap, swapon, swapoff, telinit }


   o Shutdown commands:

     { fastboot, fasthalt, halt, reboot, shutdown }
     (Or any combination of the above, so long as shutdown is included.)


   o Filesystem management commands:

     { fdisk, fsck, fsck.*, mkfs, mkfs.* }
     * = one or more of ext, ext2, minix, msdos, xia and perhaps others


   o Networking commands:

     { ifconfig, route }


3.11  /tmp : Temporary files

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



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Although data stored in /tmp may be deleted in a site-specific manner,
it is recommended that files and directories located in /tmp be deleted
whenever the system is booted.

Programs shall 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.

FHS added the recommendation that /tmp be cleaned at boot time 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





































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4.  The /usr Hierarchy

/usr is the second major section of the filesystem.  /usr is shareable,
read-only data.  That means that /usr should be shareable between
various hosts running FHS-compliant and should not be written to.  Any
information that is host-specific or varies with time is stored
elsewhere.

No large software packages should use a direct subdirectory under the
/usr hierarchy.  An exception is made for the X Window System because of
considerable precedent and widely-accepted practice.  This section of
the standard specifies the location for most such packages.

/usr -- Secondary Hierarchy
|
+-X11R6     X Window System, version 11 release 6
+-X386      X Window System, version 11 release 5 on x86 platforms
+-bin       Most user commands
+-games     Games and educational binaries
+-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
+-src       Source code


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.


















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4.1  /usr/X11R6 : X Window System, Version 11 Release 6

This hierarchy is reserved for the X Window System, version 11 release
6, and related files.

To simplify matters and make XFree86 more compatible with the X Window
System on other systems, the following symbolic links should be present:

    /usr/bin/X11 -> /usr/X11R6/bin
    /usr/lib/X11 -> /usr/X11R6/lib/X11
    /usr/include/X11 -> /usr/X11R6/include/X11

In general, software should 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.

Host-specific data in /usr/X11R6/lib/X11 should be interpreted as a
demonstration file.  Applications requiring information about the
current host (from files such as Xconfig, XF86Config, or system.twmrc)
must reference a configuration file in /etc/X11, which may be linked to
a file in /usr/X11R6/lib.


4.2  /usr/X386 : X Window System, Version 11 Release 5, on x86 platforms

This hierarchy is generally identical to /usr/X11R6; the /usr symbolic
links for X11 should point to the desired version of the X Window
System.


4.3  /usr/bin : Most user commands

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

/usr/bin -- Binaries that are not needed in single-user mode
|
+-mh        Commands for the MH mail handling system
+-X11       Symlink to /usr/X11R6/bin


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.  /usr/bin/perl, /usr/bin/python, and /usr/bin/tcl
should reference the perl, python, and tcl shell interpreters,
respectively.  They may be symlinks to the physical location of the
shell interpreters.






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

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

/usr/include -- Include files
|
+-X11       Symlink to /usr/X11R6/include/X11
+-bsd       BSD compatibility include files (if required)
+-g++       GNU C++ include files



4.5  /usr/lib : Libraries for programming and packages

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

Applications may use a single subdirectory under /usr/lib.  If an
application uses a subdirectory, all architecture-dependent data
exclusively used by the application should be placed within that
subdirectory.  For example, the perl5 subdirectory for Perl 5 modules
and libraries.

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

Some executable commands such as makewhatis and sendmail have also been
traditionally placed in /usr/lib.  makewhatis is an internal binary and
should be placed in a binary directory; users access only catman.  Newer
sendmail binaries are now placed by default in /usr/sbin; a symbolic
link should remain from /usr/lib.  Additionally, systems using Smail
should place Smail in /usr/sbin/smail, and /usr/sbin/sendmail should be
a symbolic link to it.

A symbolic link /usr/lib/X11 pointing to the lib/X11 directory of the
default X distribution is required if X is installed.

Note: No host-specific data for the X Window System should be stored in
/usr/lib/X11.  Host-specific configuration files such as Xconfig or
XF86Config should be stored in /etc/X11.  This should include
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).


4.6  /usr/local : Local hierarchy

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.




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/usr/local -- Local hierarchy
|
+-bin       Local binaries
+-games     Local game binaries
+-include   Local C header files
+-lib       Local libraries
+-sbin      Local system binaries
+-share     Local architecture-independent hierarchy
+-src       Local source code


This directory should always be empty after first installing a FHS-
compliant system.  No exceptions to this rule should be made other than
the listed directory stubs.

Locally installed software should be placed within /usr/local rather
than /usr unless it is being installed to replace or upgrade software in
/usr.

Note that 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
should not be placed outside of /usr/local without good reason.


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

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 should be placed in /sbin instead.

Typically, /usr/sbin contains networking daemons, any non-essential
administration tools, and binaries for non-critical server programs.

These server programs are used when entering the System V states known
as "run level 2" (multi-user state) and "run level 3" (networked state)
or the BSD state known as "multi-user mode".  At this point the system
is making services available to users (e.g., printer support) and to
other hosts (e.g., NFS exports).

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


4.8  /usr/share : Architecture-independent data










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Filesystem Hierarchy Standard                           October 26, 1997



/usr/share -- Architecture-independent data
|
+-dict      Word lists
+-doc       Miscellaneous documentation
+-games     Static data files for /usr/games
+-info      GNU Info system's primary directory
+-locale    Locale information
+-man       Online manuals
+-nls       Native language support
+-misc      Miscellaneous architecture-independent data
+-terminfo  Directories for terminfo database
+-tmac      troff macros not distributed with groff
+-zoneinfo  Timezone information and configuration


The /usr/share hierarchy is for all read-only architecture independent
data files.  Much of this data originally lived in /usr (man, doc) or
/usr/lib (dict, terminfo, zoneinfo).  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.

Note that Linux currently uses DBM-format database files.  While these
are not architecture-independent, they are allowed in /usr/share in
anticipation of a switch to the architecture-independent DB 2.0 format.

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

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.


4.8.1  /usr/share/dict : Word lists


Recommended files for /usr/share/dict:

{ words }

Traditionally this directory contains only the English words file, which


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is used by look(1) and various spelling programs.  words may use either
American or British spelling.  Sites that require both 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, such as the web2 "dictionary" should be included here,
if present.


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

4.8.2  /usr/share/man : Manual pages

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

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

<mandir>/<locale> -- A manual page hierarchy
|
+-man1      User programs
+-man2      System calls
+-man3      Library calls
+-man4      Special files
+-man5      File formats
+-man6      Games
+-man7      Miscellaneous
+-man8      System administration

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

The <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.



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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 shall be taken from ISO 639 (a code for the
representation of names of languages).  It shall be two characters wide
and specified with lowercase letters only.

The <territory> field shall 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.1) It shall be two characters wide and specified with
uppercase letters only.

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


____________________

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

                                 - 23 -





Filesystem Hierarchy Standard                           October 26, 1997



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 device-driver documentation or low-level
system administration commands.  These should 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 should have
the same structure as /usr/share/man.  Empty directories may be omitted
from a manual page hierarchy.  For example, if /usr/local/man has no
manual pages in section 4 (Devices), then /usr/local/man/man4 may be
omitted.

The cat page sections (cat<section>) containing formatted manual page
entries are also found within subdirectories of <mandir>/<locale>, but
are not required nor should 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 should have mh appended to all
MH manuals.  All X Window System manual pages should 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.)

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.


                                 - 24 -





Filesystem Hierarchy Standard                           October 26, 1997



   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 nonintuitive 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
     found here.

   o man8: System administration
     Documentation for programs used by system administrators for system
     operation and maintenance are documented here.  Some of these
     programs are also occasionally useful for normal users.


4.8.3  /usr/share/misc : Miscellaneous architecture-independent data
This directory contains miscellaneous architecture-independent files
which don't require a separate subdirectory under /usr/share.  It is a
required directory under /usr/share.

The following files, if present, should be located under
/usr/share/misc:


{ ascii, magic, termcap, termcap.db }

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


{ airport, birthtoken, eqnchar, getopt, gprof.callg, gprof.flat,
  inter.phone, ipfw.samp.filters, ipfw.samp.scripts, keycap.pcvt,


                                 - 25 -





Filesystem Hierarchy Standard                           October 26, 1997



  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 }


4.9  /usr/src : Source code

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
















































                                 - 26 -





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5.  The /var Hierarchy

/var -- Variable data
|
+-account   Process accounting logs (if supported)
+-cache     Application cache data
+-crash     System crash dumps (if supported)
+-games     Variable game data
+-lock      Lock files
+-log       Log files and directories
+-mail      User mailbox files
+-opt       Variable data for /opt
+-run       Files relevant to running processes
+-spool     Application spool data
+-state     Variable state information
+-tmp       Temporary files preserved between system reboots
+-yp        Network Information Service (NIS) database files

/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 should 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 should 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.

The cache, lock, log, run, spool, state, and tmp directories must be
included and used in all distributions; the account, crash, games, mail,
and yp directories must be included and used if the corresponding
applications or features are provided in the distribution.

Previous versions of the FSSTND included a /var/lib hierarchy.  For
further information, see the section on /var/state.

Several directories are `reserved' in the sense that they should not be
used arbitrarily by some new application, since they would conflict with
historical and/or local practice.  They are:


                                 - 27 -





Filesystem Hierarchy Standard                           October 26, 1997



    /var/backups
    /var/cron
    /var/lib
    /var/local
    /var/msgs
    /var/preserve


5.1  /var/account : Process accounting logs (if supported)

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).


5.2  /var/cache : Application cache data

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


/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
should 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 should
always be able to recover from manual deletion of 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

5.2.1  /var/cache/fonts : Locally-generated fonts  The directory
/var/cache/fonts should be used to store any dynamically-created fonts.
In particular, /var/cache/fonts/pk will store all of the fonts which are
automatically generated by MakeTeXPK.

There should be a link from /usr/lib/texmf/fonts/tmp to
/var/cache/fonts.  This link allows users to use single path


                                 - 28 -





Filesystem Hierarchy Standard                           October 26, 1997



/usr/lib/texmf/fonts/tfm when making changes to their TEXFONTS
environment variable.  (This is the default path for Karl Berry's TeX
tools, distributed from ftp.cs.umb.edu:/pub/tex.2 If another TeX
distribution is used, a link from the appropriate font directory to
/var/cache/fonts should be made.)

The MakeTeXPK that is distributed with dvipsk will place .pk files in
fonts/pk/<device>/<fontname> (e.g., fonts/pk/CanonCX/cmr10.300pk).  The
.pk files can be periodically purged from the /var/cache/fonts tree, or
can be moved into the /usr/lib/texmf tree.  If automatic .mf or .tfm
generators are used, they should place their data in the mf or tfm
subdirectories of /var/cache/fonts.

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


5.2.2  /var/cache/man : Locally-formatted manual pages (optional)  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.  (Note that the <locale> component
may be missing.)

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.

Man pages written to /var/cache/man may eventually be transferred to the

____________________

2. The reason that Karl Berry's tools are mentioned is that they are the
   de-facto standard for UNIX installations of  TeX.   These  tools  are
   widely used in the free UNIX community.

                                 - 29 -





Filesystem Hierarchy Standard                           October 26, 1997



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
CD-ROM, for instance), they shall 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 changed to /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

5.3  /var/crash : System crash dumps (if supported)

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


5.4  /var/games : Variable game data

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, should
remain elsewhere, such as /usr/share/games.

As for /var/state, game variable data may be placed in /var/lib as a
deprecated transitional measure.  However, this allowance will be
removed in a future release of the standard.


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/state.  Additionally, /var/games is the path traditionally used by
BSD.

END RATIONALE

5.5  /var/lock : Lock files

Lock files should be stored within the /var/lock directory structure.

Device lock files, such as the serial device lock files that were


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Filesystem Hierarchy Standard                           October 26, 1997



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/cua0 the file "LCK..cua0" would be created.

The format used for device 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.

Then, anything wishing to use /dev/cua0 can read the lock file and act
accordingly (all locks in /var/lock should be world-readable).


5.6  /var/log : Log files and directories

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

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


5.7  /var/mail : User mailbox files

This directory contains user mailbox files stored in the standard UNIX
mailbox format.


BEGIN RATIONALE

This directory was relocated 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).

END RATIONALE

5.8  /var/opt : Variable data for /opt

Variable data should 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>.







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BEGIN RATIONALE

Refer to the rationale for /opt.

END RATIONALE

5.9  /var/run : Run-time variable files

This directory contains system information files describing the system
since it was booted.  Files in this directory should be cleared (removed
or truncated as appropriate) at the beginning of the boot process.

Process identifier (PID) files, which were originally placed in /etc,
should 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.

The internal format of PID files remains unchanged.  The file should
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 should place them
in this directory.


5.10  /var/spool : Application spool data

/var/spool -- Spool directories
|
+-lpd       Printer spool directory
+-mqueue    Outgoing mail queue
+-news      News spool directory
+-rwho      Rwhod files
+-smail     Spool directories for smail
+-uucp      Spool directory for UUCP


/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.

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


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/var/lock.


5.10.1  /var/spool/lpd : Line-printer daemon print queues
/var/spool/lpd -- Printer spool directory
|
+-<printer> Spools for a specific printer (optional)


The lock file for lpd, lpd.lock, should 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.


5.10.2  /var/spool/rwho : Rwhod files

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

5.11  /var/state : Variable state information


/var/state -- Variable state information
|
+-<editor>  Editor backup files and state
+-misc      Miscellaneous state data
+-xdm       X display manager variable data
+-<pkgtool> Packaging support files
+-<package> State data for packages and subsystems


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 should never need to
modify files in /var/state 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) should use a
subdirectory of /var/state for its data.  There is one required
subdirectory, /var/state/misc, which is intended for state files that


                                 - 33 -





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don't need a subdirectory; the other subdirectories should only be
present if the application in question is included in the distribution.

/var/state/<name> is the location that should be used for all
distribution packaging support.  Different distributions may use
different names, of course.

Previous releases of this standard used the name /var/lib for this
hierarchy.  /var/lib is deprecated, but it may be used in parallel with
the required /var/state hierarchy, as a transitional measure for
application-specific data.  Note, however, that this allowance will be
removed in a future release of the standard.  Alternately, /var/lib may
be made a symbolic link to /var/state.


BEGIN RATIONALE

/usr/lib is increasingly used solely for object files or archives of
them; this is true of the current BSD UNIX variants as well as current
GNU packages.  Accordingly, the name /var/lib seemed inappropriate.

BSD uses the name /var/db for a similar directory.  This name seemed
overly constricting, as it implied a directory structure intended
primarily for database (.db) files.

END RATIONALE

5.11.1  /var/state/<editor> : Editor backup files and state

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/state (for example, GNU Emacs would place lock files in
/var/state/emacs/lock).

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

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/state.



                                 - 34 -





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END RATIONALE

5.11.2  /var/state/misc : Miscellaneous variable data

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

Note that 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).


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

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.


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

Variable data for the Network Information Service (NIS), formerly known
as the Sun Yellow Pages (YP), shall 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.

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

END RATIONALE















                                 - 35 -





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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  /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

6.1.3  /proc : Kernel and process information virtual filesystem

The proc filesystem is becoming 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 process information as well as other kernel and memory
information.


6.1.4  /sbin : Essential system binaries

Linux systems place these additional files into /sbin.




                                 - 36 -





Filesystem Hierarchy Standard                           October 26, 1997



   o Second extended filesystem commands (optional):

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


   o Boot-loader map installer:

     { 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
     combination is an instant hard reboot, it is generally advisable to
     disable the behavior before mounting the root filesystem in read-


                                 - 37 -





Filesystem Hierarchy Standard                           October 26, 1997



     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.


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

These symbolic links are required if a C or C++ compiler is installed.

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


6.1.6  /usr/src : Source code

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 shall 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

6.1.7  /var/spool/cron : cron and at jobs  This directory contains the
variable data for the cron and at programs.















                                 - 38 -





Filesystem Hierarchy Standard                           October 26, 1997



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.


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.


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>
Mike Sangrey         <mike@sojurn.lns.pa.us>
David H. Silber      <dhs@glowworm.firefly.com>
Theodore Ts'o        <tytso@athena.mit.edu>
Stephen Tweedie      <sct@dcs.ed.ac.uk>
Fred N. van Kempen   <waltje@infomagic.com>














                                 - 39 -









                                CONTENTS



1. Introduction ...................................................... 1
   1.1  Status of the Standard ....................................... 1
   1.2  Organization of the Standard ................................. 1
   1.3  Conventions .................................................. 1
   1.4  Background of the FHS ........................................ 2
   1.5  Scope ........................................................ 2
   1.6  General Guidelines ........................................... 3
   1.7  Intended Audience ............................................ 3
   1.8  Conformance with this Document ............................... 3

2. The Filesystem .................................................... 5

3. The Root Directory ................................................ 7
   3.1  /bin : Essential user command binaries (for use by all
        users) ....................................................... 8
   3.2  /boot : Static files of the boot loader ..................... 10
   3.3  /dev : Device files ......................................... 10
   3.4  /etc : Host-specific system configuration ................... 10
   3.5  /home : User home directories (optional) .................... 12
   3.6  /lib : Essential shared libraries and kernel modules ........ 12
   3.7  /mnt : Mount point for temporarily mounted filesystems ...... 13
   3.8  /opt : Add-on application software packages ................. 13
   3.9  /root : Home directory for the root user (optional) ......... 14
   3.10 /sbin : System binaries (binaries once kept in /etc) ........ 14
   3.11 /tmp : Temporary files ...................................... 15

4. The /usr Hierarchy ............................................... 17
   4.1  /usr/X11R6 : X Window System, Version 11 Release 6 .......... 18
   4.2  /usr/X386 : X Window System, Version 11 Release 5, on x86
        platforms ................................................... 18
   4.3  /usr/bin : Most user commands ............................... 18
   4.4  /usr/include : Directory for standard include files. ........ 19
   4.5  /usr/lib : Libraries for programming and packages ........... 19
   4.6  /usr/local : Local hierarchy ................................ 19
   4.7  /usr/sbin : Non-essential standard system binaries .......... 20
   4.8  /usr/share : Architecture-independent data .................. 20
   4.9  /usr/src : Source code ...................................... 26

5. The /var Hierarchy ............................................... 27
   5.1  /var/account : Process accounting logs (if supported) ....... 28
   5.2  /var/cache : Application cache data ......................... 28
   5.3  /var/crash : System crash dumps (if supported) .............. 30
   5.4  /var/games : Variable game data ............................. 30
   5.5  /var/lock : Lock files ...................................... 30
   5.6  /var/log : Log files and directories ........................ 31
   5.7  /var/mail : User mailbox files .............................. 31
   5.8  /var/opt : Variable data for /opt ........................... 31
   5.9  /var/run : Run-time variable files .......................... 32
   5.10 /var/spool : Application spool data ......................... 32
   5.11


                                    i









        /var/state : Variable state information ..................... 33
   5.12 /var/tmp : Temporary files preserved between system reboots . 35
   5.13 /var/yp : Network Information Service (NIS) database files .. 35

6. Operating System Specific Annex .................................. 36
   6.1  Linux ....................................................... 36


















































                                   ii


