File system

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DIRECTORY	DESCRIPTION
/	Primary hierarchy root and root directory of the entire file system hierarchy.
/bin	Essential command binaries that need to be available in single user mode; for all users, e.g., cat, ls, cp.
/boot	Boot loader files, e.g., kernels, initrd.
/dev	Essential devices, e.g., /dev/null.
/etc	Host-specific system-wide configuration filesThere 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 (however, the FHS restricts /etc to static configuration files and may not contain binaries). 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”.
/opt	Configuration files for add-on packages that are stored in /opt/.
/sgml	Configuration files, such as catalogs, for software that processes SGML.
/X11	Configuration files for the X Window System, version 11.
/xml	Configuration files, such as catalogs, for software that processes XML.
/home	Users’ home directories, containing saved files, personal settings, etc.
/lib	Libraries essential for the binaries in /bin/ and /sbin/.
/lib<qual>	Alternate format essential libraries. Such directories are optional, but if they exist, they have some requirements.
/media	Mount points for removable media such as CD-ROMs (appeared in FHS-2.3).
/mnt	Temporarily mounted filesystems.
/opt	Optional application software packages.
/proc	Virtual filesystem providing process and kernel information as files. In Linux, corresponds to a procfs mount.
/root	Home directory for the root user.
/sbin	Essential system binaries, e.g., init, ip, mount.
/srv	Site-specific data which are served by the system.
/tmp	Temporary files (see also /var/tmp). Often not preserved between system reboots.
/usr	Secondary hierarchy for read-only user data; contains the majority of (multi-)user utilities and applications.
/bin	Non-essential command binaries (not needed in single user mode); for all users.
/include	Standard include files.
/lib	Libraries for the binaries in /usr/bin/ and /usr/sbin/.
/lib<qual>	Alternate format libraries (optional).
/local	Tertiary hierarchy for local data, specific to this host. Typically has further subdirectories, e.g., bin/, lib/, share/.
/sbin	Non-essential system binaries, e.g., daemons for various network-services.
/share	Architecture-independent (shared) data.
/src	Source code, e.g., the kernel source code with its header files.
/X11R6	X Window System, 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 e-mail files.
/cache	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.
/lib	State information. Persistent data modified by programs as they run, e.g., databases, packaging system metadata, etc.
/lock	Lock files. Files keeping track of resources currently in use.
/log	Log files. Various logs.
/mail	Users’ mailboxes.
/opt	Variable data from add-on packages that are stored in /opt/.
/run	Information about the running system since last boot, e.g., currently logged-in users and running daemons.
/spool	Spool for tasks waiting to be processed, e.g., print queues and outgoing mail queue.
/mail	Deprecated location for users’ mailboxes.
/tmp	Temporary files to be preserved between reboots.