Filesystem Hierarchy Standard

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The Filesystem Hierarchy Standard (FHS) defines the main directories and their contents in Linux and other Unix-like computer operating systems.

Contents

[edit] Overview

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 February 14, 1994. Subsequent revisions were released on October 9, 1994 and March 28, 1995.

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 or FHS for short.

The FHS is maintained by the Free Standards Group, a non-profit organization consisting of major software and hardware vendors, such as HP, Red Hat, IBM and Dell. Still, the vast majority of the Linux distributions, including those developed by members of the Free Standards Group, do not follow this proposed standard. In particular, paths specifically created by the FHS editors, such as /srv/, do not see widespread usage. Some Unix and Linux systems break with the FHS in favor of a different approach, as in GoboLinux. Mac OS X also uses human-readable names such as /Library/, /Applications/, and /Users/ in tandem with an FHS-like system.

[edit] Directory structure

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 *nix system depending on whether certain subsystems, such as the X Window System, are installed.

Directory Description
/bin/ Essential command binaries for all users (e.g., cat, ls, cp)
/boot/ Boot loader files (e.g., kernels, initrd). Often a separate partition.
/dev/ Essential devices (e.g., /dev/null)
/etc/ Host-specific system-wide configuration files.
/etc/opt/
Configuration files for /opt/
/etc/X11/
Configuration files for the X Window System, version 11
/etc/sgml/
Configuration files for SGML.
/etc/xml/
Configuration files for XML.
/home/ Users' home directories.
/lib/ Libraries essential for the binaries in /bin/ and /sbin/
/mnt/ Temporarily mounted filesystems.
/media/ Mount points for removable media such as CD-ROMs (appeared in FHS-2.3)
/opt/ Add-on application software packages.
/proc/ Virtual filesystem documenting kernel and process status, mostly text files (e.g., uptime, network)
/root/ Home directory for the root user.
/sbin/ System administrative binaries (e.g., init, route, ifup) (system binaries)
/tmp/ Temporary files. (See also /var/tmp)
/srv/ Site-specific data which is served by the system.
/usr/ Secondary hierarchy for user shareable, read-only data.
/usr/bin/
Same as for top-level hierarchy, but non-essential (not needed to bring the system up or recover after problems).
/usr/include/
Standard include files.
/usr/lib/
Same as for top-level hierarchy.
/usr/sbin/
Same as for top-level hierarchy, but non-essential (e.g. daemons for various network-services).
/usr/share/
Architecture-independent (shared) data.
/usr/src/
Source code. (e.g. the kernel source code with its header files)
/usr/X11R6/
X Window System, Version 11 Release 6.
/usr/local/
Tertiary hierarchy for local data, specific to this host.
/var/ Variable files, such as logs, databases, websites, and temporary e-mail files.
/var/lock/
Lock files. Files keeping track of resources currently in use.
/var/log/
Log files. Various logs.
/var/mail/
Users' mail-boxes.
/var/run/
Information about the running system since last boot. (e.g. currently logged-in users and running daemons)
/var/spool/
Spool for tasks waiting to be processed. (e.g. print queues and unread mail)
/var/spool/mail/
Deprecated location for users mail-boxes.
/var/tmp/
Temporary files. Preferred to /tmp once in multi-user mode.
/var/www/
Files served by HTTP to the World Wide Web.

[edit] See also

  • GoboLinux, Linux distribution with a very different hierarchy

[edit] External links