Filesystem Hierarchy Standard
Un article de Vev.
The Filesystem Hierarchy Standard (FHS) defines the main directories and their contents in Linux operating systems. For the most part, it is a formalization and extension of the traditional BSD filesystem hierarchy.
The FHS is maintained by the Linux Foundation, a non-profit organization consisting of major software and hardware vendors, such as HP, Red Hat, IBM and Dell.
The current version is 2.3, announced on January 29, 2004.<ref>(ANNOUNCE) FHS 2.3 Released, From: Christopher Yeoh - 2004-01-29, Email Archive: freestandards-fhs-discuss (read-only), Free Standards Group, SourceForge.net</ref>
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Overview
Most Linux distributions follow the FHS and declare it their own policy to maintain FHS compliance.<ref>Red Hat reference guide on file system structure</ref><ref>SuSE Linux Enterprise Server Administration, Novell authorized courseware, by Jason W. Eckert, Novell; Course Technology, 2006; ISBN 1418837318, 9781418837310</ref><ref>Debian policy on FHS compliance</ref><ref>Ubuntu Linux File system Tree Overview - Community Ubuntu Documentation</ref>
When the FHS was created, other UNIX and Unix-like operating systems already had their own standards, notably the hier(7) description of file system layout<ref>Modèle:Man</ref> that has existed since the release of Version 7 Unix (in 1979), or the SunOS filesystem(7),<ref>SunOS 4.1.3 manual page for filesystem(7), dated 10 January 1988 (from the FreeBSD Man Pages library)</ref> later Solaris filesystem(5).<ref>Modèle:Man</ref> <ref> filesystem man page - Solaris 10 11/06 Man Pages
. Retrieved on 2011-10-15.
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Modern Linux distributions include a /sys directory as a virtual filesystem (sysfs, comparable to /proc, which is a procfs), which stores and allows modification of the devices connected to the system, whereas many traditional UNIX and Unix-like operating systems use /sys as a symbolic link to the kernel source tree.Modèle:Citation needed
Some Linux systems such as GoboLinux and Syllable Server use a completely different approach from the FHS. Modèle:Clarify
History
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 (Filesystem Standard), a filesystem hierarchy standard specific to the Linux operating system, was released on 14 February 1994. Subsequent revisions were released on 9 October 1994 and 28 March 1995.<ref>The Linux Filesystem Standard, by Garrett D'Amore, Page 45-47 in Linux Journal, July 1995, Issue 15</ref>
In early 1996, 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.
Release history
| Meaning | |
|---|---|
| Red | Old Standard/Draft; not supported |
| Yellow | Old Standard; still supported |
| Green | Current Standard |
| Blue | Future Draft |
| Version | Release Date | Notes |
|---|---|---|
| v1.0 | 1994-02-14 | FSSTND<ref>http://www.ibiblio.org/pub/Linux/docs/fsstnd/old/fsstnd-1.0/</ref> |
| v1.1 | 1994-10-09 | FSSTND<ref>http://www.ibiblio.org/pub/Linux/docs/fsstnd/old/fsstnd-1.1/</ref> |
| v1.2 | 1995-03-28 | FSSTND<ref>http://www.ibiblio.org/pub/Linux/docs/fsstnd/old/</ref> |
| v2.0 | 1997-10-26 | FHS 2.0 is the direct successor for FSSTND 1.2. Name of the standard was changed to Filesystem Hierarchy Standard.<ref>http://www.pathname.com/fhs/announce-2.0.html</ref><ref>http://www.skytel.co.cr/linux/research/1997/1116/index.htm</ref><ref>http://www.ibiblio.org/pub/Linux/docs/fsstnd/</ref> |
| v2.1 | 2000-04-12 | FHS<ref>http://www.pathname.com/fhs/announce-2.1.html</ref><ref>http://lists.debian.org/lsb-spec/2000/04/msg00005.html</ref><ref>http://cs.acadiau.ca/~jdiamond/Acadia-Linux-template-tutorial/resources/fhs-2.1.pdf</ref> |
| v2.2 | 2001-05-23 | FHS<ref>http://www.pathname.com/fhs/pub/fhs-2.2.pdf</ref> |
| v2.3 | 2004-01-29 | FHS<ref>http://www.pathname.com/fhs/pub/fhs-2.3.pdf</ref> |
| v3.0 | TBA | FHS<ref>http://www.linuxfoundation.org/collaborate/workgroups/lsb/fhs</ref> |
Directory structure
In the FHS all files and directories appear under the root directory "/", even if they are stored on different physical devices. Note however that some of these directories may or may not be present on a Unix system depending on whether certain subsystems, such as the X Window System, are installed.
The majority of these directories exist in all UNIX operating systems and are generally used in much the same way; however, the descriptions here are those used specifically for the FHS, and are not considered authoritative for platforms other than Linux.
| Directory | Description |
|---|---|
/
| Primary hierarchy root and root directory of the entire file system hierarchy. |
| Essential command binaries that need to be available in single user mode; for all users, e.g., cat, ls, cp. |
| Boot loader files, e.g., kernels, initrd; often a separate partition<ref>A separate partition is generally only used when bootloaders are incapable of reading the main filesystem (e.g. SILO does not recognize XFS) or other problems not easily resolvable by users.</ref> | |
| Essential devices, e.g., /dev/null.
|
| Host-specific system-wide configuration files There has been controversy over the meaning of the name itself. In early versions of the UNIX Implementation Document from Bell labs, /etc is referred to as the etcetera directory,<ref>Modèle:Cite manual</ref> as this directory historically held everything that did not belong elsewhere (however, the FHS restricts /etc to static configuration files and may not contain binaries).<ref>http://www.pathname.com/fhs/pub/fhs-2.3.html#ETCHOSTSPECIFICSYSTEMCONFIGURATION</ref> Since the publication of early documentation, the directory name has been re-designated in various ways. Recent interpretations include Backronyms such as "Editable Text Configuration" or "Extended Tool Chest".<ref>Define - /etc?, Posted by Cliff, March 03 2007 - Slashdot</ref> |
| Configuration files for /opt/.
|
| Configuration files for the X Window System, version 11. |
| Configuration files for SGML. |
| Configuration files for XML. |
| Users' home directories, containing saved files, personal settings, etc.; often a separate partition. |
| Libraries essential for the binaries in /bin/ and /sbin/.
|
| Mount points for removable media such as CD-ROMs (appeared in FHS-2.3). |
| Temporarily mounted filesystems. |
| Optional application software packages.<ref>http://www.pathname.com/fhs/pub/fhs-2.3.html#OPTADDONAPPLICATIONSOFTWAREPACKAGES</ref> |
| Virtual filesystem documenting kernel and process status as text files, e.g., uptime, network. In Linux, corresponds to a Procfs mount. |
| Home directory for the root user. |
| Essential system binaries, e.g., init, ip, mount. |
| Site-specific data which are served by the system. |
| Temporary files (see also /var/tmp). Often not preserved between system reboots.
|
| Secondary hierarchy for read-only user data; contains the majority of (multi-)user utilities and applications.<ref>Should be shareable and read-only, cf. http://www.pathname.com/fhs/pub/fhs-2.3.html.</ref> |
| Non-essential command binaries (not needed in single user mode); for all users. |
| Standard include files. |
| Libraries for the binaries in /usr/bin/ and /usr/sbin/.
|
| Non-essential system binaries, e.g., daemons for various network-services. |
| Architecture-independent (shared) data. |
| Source code, e.g., the kernel source code with its header files. |
| X Window System, Version 11, Release 6. |
| Tertiary hierarchy for local data, specific to this host. Typically has further subdirectories, e.g., bin/, lib/, share/.<ref>Historically and strictly according to the standard, /usr/local/ is for data that must be stored on the local host (as opposed to /usr/, which may be mounted across a network). Most of the time /usr/local/ is used for installing software/data that are not part of the standard operating system distribution (in such case, /usr/ would only contain software/data that are part of the standard operating system distribution). It is possible that the FHS standard may in the future be changed to reflect this de-facto convention).</ref>
|
| Variable files—files whose content is expected to continually change during normal operation of the system—such as logs, spool files, and temporary e-mail files. Sometimes a separate partition. |
| Application cache data. Such data are locally generated as a result of time-consuming I/O or calculation. The application must be able to regenerate or restore the data. The cached files can be deleted without loss of data. |
| State information. Persistent data modified by programs as they run, e.g., databases, packaging system metadata, etc. |
| Lock files. Files keeping track of resources currently in use. |
| Log files. Various logs. |
| Users' mailboxes. |
| Information about the running system since last boot, e.g., currently logged-in users and running daemons. |
| Spool for tasks waiting to be processed, e.g., print queues and unread mail. |
| Deprecated location for users' mailboxes. |
| Temporary files to be preserved between reboots. |
References
External links
- Official Home of the Filesystem Hierarchy Standard (FHS), The Linux Foundation
- objectroot – a proposal for a new filesystem hierarchy, based on object-oriented design principles
- Fortune Cookies through the /proc Filesystem
- The Dotted Standard Filename Hierarchy, yet another very different hierarchy (used in cLIeNUX) (mirror)
