ITSC1358 – UNIX/Linux Administration
Prof. Michael P. Harris
Linux (FHS) Filesystem Hierarchy Standard
In the Linux FHS (Filesystem Hierarchy Standard) all files and directories exist under the one,
and only one, root directory “/”, even if they are stored on different physical or virtual devices
or filesystems. Note that some of these directories may or may not be present on a given Linux
system depending on whether certain subsystems, such as X―Windows, are installed.
The majority of these directories also exist in the UNIX operating system 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. This list is not an exhaustive
list of the FHS directories.
Directory
Description
/
The hierarchy top-level root directory of the entire filesystem.
/bin
Essential command binaries that need to be available to boot the OS into
single user mode; for all users. ex., cd, cat, ls, cp, mv, rm.
/boot
Boot loader files, e.g., kernel, initrd.
/dev
Essential device files, ex., /dev/null.
/etc
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, as this directory historically held
everything that did not belong elsewhere. FHS however, restricts /etc to
static configuration files and scripts and may not contain binaries. Since the
publication of early GNU documentation, the directory name has been redesignated in various ways. Recent interpretations include backronyms such
as “Editable Text Configuration” or “Extended Tool Chest”.
/etc/default
Backup copies of default system—wide configuration files.
/etc/profile.d Contains add-on scripts to run at user login. Script names must end in .sh.
/etc/skel
Default user (new user) home directory configuration scripts. Hidden “.” files.
/etc/X11
Configuration files for the X—Window System, version 11.
/home
All the users’ (except root) home directories, containing the individual users’
configuration scripts, saved files, personal settings, etc.
/lib
Libraries essential for the binaries in /bin/ and /sbin/.
/media
Mount points for removable media such as Flash Drives (enhances /mnt).
/mnt
Mount points for temporarily mounted filesystems such as CD-ROMs.
/opt
Optional application software packages. (Rarely used in Linux)
/proc
Virtual filesystem providing information about process and kernel information
in/as files. In Linux, this corresponds to a procfs mount.
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ITSC1358 – UNIX/Linux Administration
Prof. Michael P. Harris
/root
Home directory for the Super User (root).
/sbin
Essential system binaries. ex., init, mkfs, fsck, mount.
/tmp
Temporary files (see also /var/tmp). Often deleted between reboots.
/usr
Secondary hierarchy for read-only user data; contains the majority of shared
(multi—)user utilities and applications.
/usr/bin
Non-essential command binaries (see /bin); for all users. May contain links to
all available user utilities/commands (binaries)
/usr/include
Standard include files for ‘C’ programmers.
/usr/lib
Libraries for the binaries in /usr/bin/ and /usr/sbin/.
/usr/local
Tertiary hierarchy for local shared data, specific to this host. May be used
instead of, or in addition to, /usr/share.
/usr/sbin
Non-essential system binaries. e.g., daemons for various network-services.
/usr/share
Architecture-independent user shared data. May be used instead of, or
in addition to, /usr/local, but more commonly in use.
/usr/src
Source code. e.g., kernel and utility ‘C’ source code with it header files.
/usr/X11R6
The X—Windows window manager, Version 11, Release 6.
/var
Variable files —files whose content is expected to continually change during
normal operation of the system —such as logs, spool files, and temporary files.
/var/cache
Application cached data. Data that is locally generated as a result of timeconsuming I/O or calculations. The applications must be able to regenerate
or restore the data. The cached files can be deleted without loss of data.
/var/lib
State information. Persistent data modified by programs as they run.
ex., databases, packaging system metadata, etc.
/var/lock
Lock files. Files keeping track of resources currently in use.
/var/log
Log files. Various OS and application logs.
/var/run
Information about the running system since last boot.
e.g., currently logged-in users and running daemons.
/var/spool
Spool files for tasks waiting to be processed. ex., print queues.
/var/tmp
Temporary files to be preserved between reboots. (see also /tmp)
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