The Filesystem Hierarchy Standard (FHS) defines the main directories and their contents in GNU/Linux and other Unix-like computer operating systems.
The process of developing a standard FileSystem hierarchy began in August 1993 with an effort to restructure the file and directory structure of GNU/Linux. The FSSTND (Filesystem Standard), a filesystem hierarchy standard specific to the GNU/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 GNU/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, IBM and Dell. Still, the vast majority of the GNU/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 /media/ and /srv/, do not see widespread usage. Some Unix and GNU/Linux systems break with the FHS in favour of a different approach, as in Gobo GNU/Linux.
All files and directories appear under the root_directory “/”, even if stored on different physical devices.
A description of the hierarchy specified in the FHS
Essential command executable (binaries) for all users (e.g., cat, ls, cp)
(especially files required to boot or rescue the system)
Boot loader, kernels and initrd files
Devices files (e.g., :/dev/null)
Host-specific system-wide configuration files (from et cetera)
Users' home directories
Libraries essential for the binaries in /bin/ and /sbin/
(library required to boot or rescue the system)
Some files and fragment that were “recovered” during the previous fsck (Not part of FHS)
Temporarily mounted filesystems
Mount points for removable media such as CD-ROMs (appeared in FHS-2.3)
Add-on application software packages
Pre-compiled, non Hyperbola binary distribution (tar'ed..) goes here.
- /opt/bin/ : Same as for top-level hierarchy
- /opt/include/ : Same as for top-level hierarchy
- /opt/lib/ : Same as for top-level hierarchy
- /opt/sbin/ : Same as for top-level hierarchy
- /opt/share/ : Same as for top-level hierarchy
Virtual filesystem documenting kernel and process status, mostly text files (e.g., uptime, network)
Home directory for the root user
System administrative binaries (e.g., init, route, ifup) (system binaries)
(files required to boot or rescue the system)
SE-Linux runtime settings (Not part of FHS).
Site-specific data which is served by the system (Not part of FHS).
The filesystem for exporting kernel objects.
(many /proc/* files should have been here…)
Secondary hierarchy for shareable, read-only data (formerly from UNIX source repository, now from UNIX system resources)
(files that are not-required to boot or rescue the system)
- /usr/bin/ : Same as for top-level hierarchy
- /usr/include/ : Standard include files
- /usr/lib/ : Same as for top-level hierarchy
- /usr/sbin/ : Same as for top-level hierarchy
- /usr/share/ : Architecture-independent (shared) data
- /usr/src/ : Source code (to build debian packages. see also /usr/local/src/)
- /usr/X11R6/ : X Window System, Version 11 Release 6
- /usr/local/ : Tertiary hierarchy for local data installed by the system administrator
- /usr/local/bin : locally compiled binaries, local shell script, etc.
- /usr/local/src : Source code (place where to extract and build non debian'ized stuffs)
Variable data, such as logs, databases, websites, and temporary spool (e-mail..) files
This wiki article is based on DebianWiki. We may have removed non-FSDG bits from it.