Linux Filesystem Hierarchy

 Linux Filesystem Hierarchy

This article describes Linux Filesystem Hierarchy

/

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 device files, e.g., /dev/null.

/etc

Host-specific system-wide configuration file

 etc/init.d/

The term 'init' is short for initialization. This directory contains script to control the system or to start and stop the daemons (background process). The 'init' is a daemon process that continues running until the system is shut down.

 /etc/skel

The /etc/skel directory contains files and directories that are automatically copied over to a new user's home directory when such user is created by the useradd program.

/etc/opt

Configuration files for add-on packages that are stored in /opt.

/etc/sgml

Configuration files, such as catalogs, for software that processes SGML.

/etc/X11

Configuration files for the X Window System, version 11.

/etc/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 in 2004).

/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. Generally automatically generated and populated by the system, on the fly.

/root

Home directory for the root user.

/run

Run-time variable data: Information about the running system since last boot, e.g., currently logged-in users and running daemons. Files under this directory must be either removed or truncated at the beginning of the boot process; but this is not necessary on systems that provide this directory as a temporary filesystem (tmpfs).

/sbin

Essential system binaries, e.g., fsck, init, route.

/srv

Site-specific data served by this system, such as data and scripts for web servers, data offered by FTP servers, and repositories for version control systems (appeared in FHS-2.3 in 2004).

/sys

Contains information about devices, drivers, and some kernel features.

/tmp

Temporary files (see also /var/tmp). Often not preserved between system reboots, and may be severely size restricted.

/usr

Secondary hierarchy for read-only user data; contains the majority of (multi-)user utilities and applications.

/usr/bin

Non-essential command binaries (not needed in single user mode); for all users.

/usr/include

Standard include files.

/usr/lib

Libraries for the binaries in /usr/bin and /usr/sbin.

/usr/lib<qual>

Alternate format libraries, e.g. /usr/lib32 for 32-bit libraries on a 64-bit machine (optional).

/usr/local

Tertiary hierarchy for local data, specific to this host. Typically has further subdirectories, e.g., bin, lib, share.

/usr/sbin

Non-essential system binaries, 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 (up to FHS-2.3, optional).

/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.

/var/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.

/var/lib

State information. Persistent data modified by programs as they run, e.g., databases, packaging system metadata, etc.

/var/lock

Lock files. Files keeping track of resources currently in use.

/var/log

Log files. Various logs.

/var/mail

Mailbox files. In some distributions, these files may be located in the deprecated /var/spool/mail.

/var/opt

Variable data from add-on packages that are stored in /opt.

/var/run

Run-time variable data. This directory contains system information data describing the system since it was booted.
In FHS 3.0, /var/run is replaced by /run; a system should either continue to provide a /var/run directory, or provide a symbolic link from /var/run to /run, for backwards compatibility.[11]

/var/spool

Spool for tasks waiting to be processed, e.g., print queues and outgoing mail queue.

/var/spool/mail

Deprecated location for users' mailboxes.[12]

/var/tmp

Temporary files to be preserved between reboots.


Ref : For more details about File System Hierarchy, Please visit https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard