Directory Structure
In the FHS all files and directories appear under the root directory "/", even if they are stored on different physical or virtual 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. |
|
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, 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". |
|
Configuration files for /opt/. |
|
Configuration files for SGML. |
|
Configuration files for the X Window System, version 11. |
|
Configuration files for XML. |
|
Users' home directories, containing saved files, personal settings, etc. |
|
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. |
|
Virtual filesystem providing information about processes and kernel information as files. 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. |
|
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/. |
|
Tertiary hierarchy for local data, specific to this host. Typically has further subdirectories, e.g., bin/, lib/, share/. |
|
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. |
|
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. |
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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. |
Read more about this topic: Filesystem Hierarchy Standard
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