NAME | DESCRIPTION | GENERAL STRUCTURE | RUNTIME DATA | VENDOR-SUPPLIED OPERATING SYSTEM RESOURCES | PERSISTENT VARIABLE SYSTEM DATA | VIRTUAL KERNEL AND API FILE SYSTEMS | COMPATIBILITY SYMLINKS | HOME DIRECTORY | UNPRIVILEGED WRITE ACCESS | NODE TYPES | SYSTEM PACKAGES | USER PACKAGES | SEE ALSO | NOTES | COLOPHON

FILE-HIERARCHY(7)              file-hierarchy              FILE-HIERARCHY(7)

NAME         top

       file-hierarchy - File system hierarchy overview

DESCRIPTION         top

       Operating systems using the systemd(1) system and service manager are
       organized based on a file system hierarchy inspired by UNIX, more
       specifically the hierarchy described in the File System Hierarchy[1]
       specification and hier(7). This manual page describes a more minimal,
       modernized subset of these specifications that defines more strictly
       the suggestions and restrictions systemd makes on the file system
       hierarchy.

       Many of the paths described here can be queried with the
       systemd-path(1) tool.

GENERAL STRUCTURE         top

       /
           The file system root. Usually writable, but this is not required.
           Possibly a temporary file system ("tmpfs"). Not shared with other
           hosts (unless read-only).

       /boot
           The boot partition used for bringing up the system. On EFI
           systems, this is possibly the EFI System Partition, also see
           systemd-gpt-auto-generator(8). This directory is usually strictly
           local to the host, and should be considered read-only, except
           when a new kernel or boot loader is installed. This directory
           only exists on systems that run on physical or emulated hardware
           that requires boot loaders.

       /etc
           System-specific configuration. This directory may or may not be
           read-only. Frequently, this directory is pre-populated with
           vendor-supplied configuration files, but applications should not
           make assumptions about this directory being fully populated or
           populated at all, and should fall back to defaults if
           configuration is missing.

       /home
           The location for normal user's home directories. Possibly shared
           with other systems, and never read-only. This directory should
           only be used for normal users, never for system users. This
           directory and possibly the directories contained within it might
           only become available or writable in late boot or even only after
           user authentication. This directory might be placed on
           limited-functionality network file systems, hence applications
           should not assume the full set of file API is available on this
           directory. Applications should generally not reference this
           directory directly, but via the per-user $HOME environment
           variable, or via the home directory field of the user database.

       /root
           The home directory of the root user. The root user's home
           directory is located outside of /home in order to make sure the
           root user may log in even without /home being available and
           mounted.

       /srv
           The place to store general server payload, managed by the
           administrator. No restrictions are made how this directory is
           organized internally. Generally writable, and possibly shared
           among systems. This directory might become available or writable
           only very late during boot.

       /tmp
           The place for small temporary files. This directory is usually
           mounted as a "tmpfs" instance, and should hence not be used for
           larger files. (Use /var/tmp for larger files.) Since the
           directory is accessible to other users of the system, it is
           essential that this directory is only written to with the
           mkstemp(3), mkdtemp(3) and related calls. This directory is
           usually flushed at boot-up. Also, files that are not accessed
           within a certain time are usually automatically deleted. If
           applications find the environment variable $TMPDIR set, they
           should prefer using the directory specified in it over directly
           referencing /tmp (see environ(7) and IEEE Std 1003.1[2] for
           details).

RUNTIME DATA         top

       /run
           A "tmpfs" file system for system packages to place runtime data
           in. This directory is flushed on boot, and generally writable for
           privileged programs only. Always writable.

       /run/log
           Runtime system logs. System components may place private logs in
           this directory. Always writable, even when /var/log might not be
           accessible yet.

       /run/user
           Contains per-user runtime directories, each usually individually
           mounted "tmpfs" instances. Always writable, flushed at each
           reboot and when the user logs out. User code should not reference
           this directory directly, but via the $XDG_RUNTIME_DIR environment
           variable, as documented in the XDG Base Directory
           Specification[3].

VENDOR-SUPPLIED OPERATING SYSTEM RESOURCES         top

       /usr
           Vendor-supplied operating system resources. Usually read-only,
           but this is not required. Possibly shared between multiple hosts.
           This directory should not be modified by the administrator,
           except when installing or removing vendor-supplied packages.

       /usr/bin
           Binaries and executables for user commands that shall appear in
           the $PATH search path. It is recommended not to place binaries in
           this directory that are not useful for invocation from a shell
           (such as daemon binaries); these should be placed in a
           subdirectory of /usr/lib instead.

       /usr/include
           C and C++ API header files of system libraries.

       /usr/lib
           Static, private vendor data that is compatible with all
           architectures (though not necessarily architecture-independent).
           Note that this includes internal executables or other binaries
           that are not regularly invoked from a shell. Such binaries may be
           for any architecture supported by the system. Do not place public
           libraries in this directory, use $libdir (see below), instead.

       /usr/lib/arch-id
           Location for placing dynamic libraries into, also called $libdir.
           The architecture identifier to use is defined on Multiarch
           Architecture Specifiers (Tuples)[4] list. Legacy locations of
           $libdir are /usr/lib, /usr/lib64. This directory should not be
           used for package-specific data, unless this data is
           architecture-dependent, too. To query $libdir for the primary
           architecture of the system, invoke:

               # systemd-path system-library-arch

       /usr/share
           Resources shared between multiple packages, such as
           documentation, man pages, time zone information, fonts and other
           resources. Usually, the precise location and format of files
           stored below this directory is subject to specifications that
           ensure interoperability.

       /usr/share/doc
           Documentation for the operating system or system packages.

       /usr/share/factory/etc
           Repository for vendor-supplied default configuration files. This
           directory should be populated with pristine vendor versions of
           all configuration files that may be placed in /etc. This is
           useful to compare the local configuration of a system with vendor
           defaults and to populate the local configuration with defaults.

       /usr/share/factory/var
           Similar to /usr/share/factory/etc, but for vendor versions of
           files in the variable, persistent data directory /var.

PERSISTENT VARIABLE SYSTEM DATA         top

       /var
           Persistent, variable system data. Must be writable. This
           directory might be pre-populated with vendor-supplied data, but
           applications should be able to reconstruct necessary files and
           directories in this subhierarchy should they be missing, as the
           system might start up without this directory being populated.
           Persistency is recommended, but optional, to support ephemeral
           systems. This directory might become available or writable only
           very late during boot. Components that are required to operate
           during early boot hence shall not unconditionally rely on this
           directory.

       /var/cache
           Persistent system cache data. System components may place
           non-essential data in this directory. Flushing this directory
           should have no effect on operation of programs, except for
           increased runtimes necessary to rebuild these caches.

       /var/lib
           Persistent system data. System components may place private data
           in this directory.

       /var/log
           Persistent system logs. System components may place private logs
           in this directory, though it is recommended to do most logging
           via the syslog(3) and sd_journal_print(3) calls.

       /var/spool
           Persistent system spool data, such as printer or mail queues.

       /var/tmp
           The place for larger and persistent temporary files. In contrast
           to /tmp, this directory is usually mounted from a persistent
           physical file system and can thus accept larger files. (Use /tmp
           for smaller files.) This directory is generally not flushed at
           boot-up, but time-based cleanup of files that have not been
           accessed for a certain time is applied. The same security
           restrictions as with /tmp apply, and hence only mkstemp(3),
           mkdtemp(3) or similar calls should be used to make use of this
           directory. If applications find the environment variable $TMPDIR
           set, they should prefer using the directory specified in it over
           directly referencing /var/tmp (see environ(7) for details).

VIRTUAL KERNEL AND API FILE SYSTEMS         top

       /dev
           The root directory for device nodes. Usually, this directory is
           mounted as a "devtmpfs" instance, but might be of a different
           type in sandboxed/containerized setups. This directory is managed
           jointly by the kernel and systemd-udevd(8), and should not be
           written to by other components. A number of special purpose
           virtual file systems might be mounted below this directory.

       /dev/shm
           Place for POSIX shared memory segments, as created via
           shm_open(3). This directory is flushed on boot, and is a "tmpfs"
           file system. Since all users have write access to this directory,
           special care should be taken to avoid name clashes and
           vulnerabilities. For normal users, shared memory segments in this
           directory are usually deleted when the user logs out. Usually, it
           is a better idea to use memory mapped files in /run (for system
           programs) or $XDG_RUNTIME_DIR (for user programs) instead of
           POSIX shared memory segments, since these directories are not
           world-writable and hence not vulnerable to security-sensitive
           name clashes.

       /proc
           A virtual kernel file system exposing the process list and other
           functionality. This file system is mostly an API to interface
           with the kernel and not a place where normal files may be stored.
           For details, see proc(5). A number of special purpose virtual
           file systems might be mounted below this directory.

       /proc/sys
           A hierarchy below /proc that exposes a number of kernel tunables.
           The primary way to configure the settings in this API file tree
           is via sysctl.d(5) files. In sandboxed/containerized setups, this
           directory is generally mounted read-only.

       /sys
           A virtual kernel file system exposing discovered devices and
           other functionality. This file system is mostly an API to
           interface with the kernel and not a place where normal files may
           be stored. In sandboxed/containerized setups, this directory is
           generally mounted read-only. A number of special purpose virtual
           file systems might be mounted below this directory.

COMPATIBILITY SYMLINKS         top

       /bin, /sbin, /usr/sbin
           These compatibility symlinks point to /usr/bin, ensuring that
           scripts and binaries referencing these legacy paths correctly
           find their binaries.

       /lib
           This compatibility symlink points to /usr/lib, ensuring that
           programs referencing this legacy path correctly find their
           resources.

       /lib64
           On some architecture ABIs, this compatibility symlink points to
           $libdir, ensuring that binaries referencing this legacy path
           correctly find their dynamic loader. This symlink only exists on
           architectures whose ABI places the dynamic loader in this path.

       /var/run
           This compatibility symlink points to /run, ensuring that programs
           referencing this legacy path correctly find their runtime data.

HOME DIRECTORY         top

       User applications may want to place files and directories in the
       user's home directory. They should follow the following basic
       structure. Note that some of these directories are also standardized
       (though more weakly) by the XDG Base Directory Specification[3].
       Additional locations for high-level user resources are defined by
       xdg-user-dirs[5].

       ~/.cache
           Persistent user cache data. User programs may place non-essential
           data in this directory. Flushing this directory should have no
           effect on operation of programs, except for increased runtimes
           necessary to rebuild these caches. If an application finds
           $XDG_CACHE_HOME set, it should use the directory specified in it
           instead of this directory.

       ~/.config
           Application configuration and state. When a new user is created,
           this directory will be empty or not exist at all. Applications
           should fall back to defaults should their configuration or state
           in this directory be missing. If an application finds
           $XDG_CONFIG_HOME set, it should use the directory specified in it
           instead of this directory.

       ~/.local/bin
           Executables that shall appear in the user's $PATH search path. It
           is recommended not to place executables in this directory that
           are not useful for invocation from a shell; these should be
           placed in a subdirectory of ~/.local/lib instead. Care should be
           taken when placing architecture-dependent binaries in this place,
           which might be problematic if the home directory is shared
           between multiple hosts with different architectures.

       ~/.local/lib
           Static, private vendor data that is compatible with all
           architectures.

       ~/.local/lib/arch-id
           Location for placing public dynamic libraries. The architecture
           identifier to use is defined on Multiarch Architecture Specifiers
           (Tuples)[4] list.

       ~/.local/share
           Resources shared between multiple packages, such as fonts or
           artwork. Usually, the precise location and format of files stored
           below this directory is subject to specifications that ensure
           interoperability. If an application finds $XDG_DATA_HOME set, it
           should use the directory specified in it instead of this
           directory.

UNPRIVILEGED WRITE ACCESS         top

       Unprivileged processes generally lack write access to most of the
       hierarchy.

       The exceptions for normal users are /tmp, /var/tmp, /dev/shm, as well
       as the home directory $HOME (usually found below /home) and the
       runtime directory $XDG_RUNTIME_DIR (found below /run/user) of the
       user, which are all writable.

       For unprivileged system processes, only /tmp, /var/tmp and /dev/shm
       are writable. If an unprivileged system process needs a private
       writable directory in /var or /run, it is recommended to either
       create it before dropping privileges in the daemon code, to create it
       via tmpfiles.d(5) fragments during boot, or via the RuntimeDirectory=
       directive of service units (see systemd.unit(5) for details).

NODE TYPES         top

       Unix file systems support different types of file nodes, including
       regular files, directories, symlinks, character and block device
       nodes, sockets and FIFOs.

       It is strongly recommended that /dev is the only location below which
       device nodes shall be placed. Similarly, /run shall be the only
       location to place sockets and FIFOs. Regular files, directories and
       symlinks may be used in all directories.

SYSTEM PACKAGES         top

       Developers of system packages should follow strict rules when placing
       their own files in the file system. The following table lists
       recommended locations for specific types of files supplied by the
       vendor.

       Table 1. System Package Vendor Files Locations
       ┌─────────────────────────┬───────────────────────────┐
       │Directory                Purpose                   │
       ├─────────────────────────┼───────────────────────────┤
       │/usr/bin                 │ Package executables that  │
       │                         │ shall appear in the $PATH │
       │                         │ executable search path,   │
       │                         │ compiled for any of the   │
       │                         │ supported architectures   │
       │                         │ compatible with the       │
       │                         │ operating system. It is   │
       │                         │ not recommended to place  │
       │                         │ internal binaries or      │
       │                         │ binaries that are not     │
       │                         │ commonly invoked from the │
       │                         │ shell in this directory,  │
       │                         │ such as daemon binaries.  │
       │                         │ As this directory is      │
       │                         │ shared with most other    │
       │                         │ packages of the system,   │
       │                         │ special care should be    │
       │                         │ taken to pick unique      │
       │                         │ names for files placed    │
       │                         │ here, that are unlikely   │
       │                         │ to clash with other       │
       │                         │ package's files.          │
       ├─────────────────────────┼───────────────────────────┤
       │/usr/lib/arch-id         │ Public shared libraries   │
       │                         │ of the package. As above, │
       │                         │ be careful with using too │
       │                         │ generic names, and pick   │
       │                         │ unique names for your     │
       │                         │ libraries to place here   │
       │                         │ to avoid name clashes.    │
       ├─────────────────────────┼───────────────────────────┤
       │/usr/lib/package         │ Private static vendor     │
       │                         │ resources of the package, │
       │                         │ including private         │
       │                         │ binaries and libraries,   │
       │                         │ or any other kind of      │
       │                         │ read-only vendor data.    │
       ├─────────────────────────┼───────────────────────────┤
       │/usr/lib/arch-id/package │ Private other vendor      │
       │                         │ resources of the package  │
       │                         │ that are                  │
       │                         │ architecture-specific and │
       │                         │ cannot be shared between  │
       │                         │ architectures. Note that  │
       │                         │ this generally does not   │
       │                         │ include private           │
       │                         │ executables since         │
       │                         │ binaries of a specific    │
       │                         │ architecture may be       │
       │                         │ freely invoked from any   │
       │                         │ other supported system    │
       │                         │ architecture.             │
       ├─────────────────────────┼───────────────────────────┤
       │/usr/include/package     │ Public C/C++ APIs of      │
       │                         │ public shared libraries   │
       │                         │ of the package.           │
       └─────────────────────────┴───────────────────────────┘

       Additional static vendor files may be installed in the /usr/share
       hierarchy to the locations defined by the various relevant
       specifications.

       During runtime, and for local configuration and state, additional
       directories are defined:

       Table 2. System Package Variable Files Locations
       ┌───────────────────┬───────────────────────────┐
       │Directory          Purpose                   │
       ├───────────────────┼───────────────────────────┤
       │/etc/package       │ System-specific           │
       │                   │ configuration for the     │
       │                   │ package. It is            │
       │                   │ recommended to default to │
       │                   │ safe fallbacks if this    │
       │                   │ configuration is missing, │
       │                   │ if this is possible.      │
       │                   │ Alternatively, a          │
       │                   │ tmpfiles.d(5) fragment    │
       │                   │ may be used to copy or    │
       │                   │ symlink the necessary     │
       │                   │ files and directories     │
       │                   │ from /usr/share/factory   │
       │                   │ during boot, via the "L"  │
       │                   │ or "C" directives.        │
       ├───────────────────┼───────────────────────────┤
       │/run/package       │ Runtime data for the      │
       │                   │ package. Packages must be │
       │                   │ able to create the        │
       │                   │ necessary subdirectories  │
       │                   │ in this tree on their     │
       │                   │ own, since the directory  │
       │                   │ is flushed automatically  │
       │                   │ on boot. Alternatively, a │
       │                   │ tmpfiles.d(5) fragment    │
       │                   │ may be used to create the │
       │                   │ necessary directories     │
       │                   │ during boot.              │
       │                   │ Alternatively, the        │
       │                   │ RuntimeDirectory=         │
       │                   │ directive of service      │
       │                   │ units may be used (see    │
       │                   │ systemd.unit(5) for       │
       │                   │ details.)                 │
       ├───────────────────┼───────────────────────────┤
       │/run/log/package   │ Runtime log data for the  │
       │                   │ package. As above, the    │
       │                   │ package needs to make     │
       │                   │ sure to create this       │
       │                   │ directory if necessary,   │
       │                   │ as it will be flushed on  │
       │                   │ every boot.               │
       ├───────────────────┼───────────────────────────┤
       │/var/cache/package │ Persistent cache data of  │
       │                   │ the package. If this      │
       │                   │ directory is flushed, the │
       │                   │ application should work   │
       │                   │ correctly on next         │
       │                   │ invocation, though        │
       │                   │ possibly slowed down due  │
       │                   │ to the need to rebuild    │
       │                   │ any local cache files.    │
       │                   │ The application must be   │
       │                   │ capable of recreating     │
       │                   │ this directory should it  │
       │                   │ be missing and necessary. │
       ├───────────────────┼───────────────────────────┤
       │/var/lib/package   │ Persistent private data   │
       │                   │ of the package. This is   │
       │                   │ the primary place to put  │
       │                   │ persistent data that does │
       │                   │ not fall into the other   │
       │                   │ categories listed.        │
       │                   │ Packages should be able   │
       │                   │ to create the necessary   │
       │                   │ subdirectories in this    │
       │                   │ tree on their own, since  │
       │                   │ the directory might be    │
       │                   │ missing on boot.          │
       │                   │ Alternatively, a          │
       │                   │ tmpfiles.d(5) fragment    │
       │                   │ may be used to create the │
       │                   │ necessary directories     │
       │                   │ during boot.              │
       ├───────────────────┼───────────────────────────┤
       │/var/log/package   │ Persistent log data of    │
       │                   │ the package. As above,    │
       │                   │ the package should make   │
       │                   │ sure to create this       │
       │                   │ directory if necessary,   │
       │                   │ as it might be missing.   │
       ├───────────────────┼───────────────────────────┤
       │/var/spool/package │ Persistent spool/queue    │
       │                   │ data of the package. As   │
       │                   │ above, the package should │
       │                   │ make sure to create this  │
       │                   │ directory if necessary,   │
       │                   │ as it might be missing.   │
       └───────────────────┴───────────────────────────┘

USER PACKAGES         top

       Programs running in user context should follow strict rules when
       placing their own files in the user's home directory. The following
       table lists recommended locations in the home directory for specific
       types of files supplied by the vendor if the application is installed
       in the home directory. (Note, however, that user applications
       installed system-wide should follow the rules outlined above
       regarding placing vendor files.)

       Table 3. User Package Vendor File Locations
       ┌─────────────────────────────┬───────────────────────────┐
       │Directory                    Purpose                   │
       ├─────────────────────────────┼───────────────────────────┤
       │~/.local/bin                 │ Package executables that  │
       │                             │ shall appear in the $PATH │
       │                             │ executable search path.   │
       │                             │ It is not recommended to  │
       │                             │ place internal            │
       │                             │ executables or            │
       │                             │ executables that are not  │
       │                             │ commonly invoked from the │
       │                             │ shell in this directory,  │
       │                             │ such as daemon            │
       │                             │ executables. As this      │
       │                             │ directory is shared with  │
       │                             │ most other packages of    │
       │                             │ the user, special care    │
       │                             │ should be taken to pick   │
       │                             │ unique names for files    │
       │                             │ placed here, that are     │
       │                             │ unlikely to clash with    │
       │                             │ other package's files.    │
       ├─────────────────────────────┼───────────────────────────┤
       │~/.local/lib/arch-id         │ Public shared libraries   │
       │                             │ of the package. As above, │
       │                             │ be careful with using too │
       │                             │ generic names, and pick   │
       │                             │ unique names for your     │
       │                             │ libraries to place here   │
       │                             │ to avoid name clashes.    │
       ├─────────────────────────────┼───────────────────────────┤
       │~/.local/lib/package         │ Private, static vendor    │
       │                             │ resources of the package, │
       │                             │ compatible with any       │
       │                             │ architecture, or any      │
       │                             │ other kind of read-only   │
       │                             │ vendor data.              │
       ├─────────────────────────────┼───────────────────────────┤
       │~/.local/lib/arch-id/package │ Private other vendor      │
       │                             │ resources of the package  │
       │                             │ that are                  │
       │                             │ architecture-specific and │
       │                             │ cannot be shared between  │
       │                             │ architectures.            │
       └─────────────────────────────┴───────────────────────────┘

       Additional static vendor files may be installed in the ~/.local/share
       hierarchy to the locations defined by the various relevant
       specifications.

       During runtime, and for local configuration and state, additional
       directories are defined:

       Table 4. User Package Variable File Locations
       ┌─────────────────────────┬───────────────────────────┐
       │Directory                Purpose                   │
       ├─────────────────────────┼───────────────────────────┤
       │~/.config/package        │ User-specific             │
       │                         │ configuration and state   │
       │                         │ for the package. It is    │
       │                         │ required to default to    │
       │                         │ safe fallbacks if this    │
       │                         │ configuration is missing. │
       ├─────────────────────────┼───────────────────────────┤
       │$XDG_RUNTIME_DIR/package │ User runtime data for the │
       │                         │ package.                  │
       ├─────────────────────────┼───────────────────────────┤
       │~/.cache/package         │ Persistent cache data of  │
       │                         │ the package. If this      │
       │                         │ directory is flushed, the │
       │                         │ application should work   │
       │                         │ correctly on next         │
       │                         │ invocation, though        │
       │                         │ possibly slowed down due  │
       │                         │ to the need to rebuild    │
       │                         │ any local cache files.    │
       │                         │ The application must be   │
       │                         │ capable of recreating     │
       │                         │ this directory should it  │
       │                         │ be missing and necessary. │
       └─────────────────────────┴───────────────────────────┘

SEE ALSO         top

       systemd(1), hier(7), systemd-path(1), systemd-gpt-auto-generator(8),
       sysctl.d(5), tmpfiles.d(5), pkg-config(1), systemd.unit(5)

NOTES         top

        1. File System Hierarchy
           http://refspecs.linuxfoundation.org/FHS_2.3/fhs-2.3.html

        2. IEEE Std 1003.1
           http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03

        3. XDG Base Directory Specification
           http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

        4. Multiarch Architecture Specifiers (Tuples)
           https://wiki.debian.org/Multiarch/Tuples

        5. xdg-user-dirs
           https://www.freedesktop.org/wiki/Software/xdg-user-dirs/

COLOPHON         top

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       project.  Information about the project can be found at 
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       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
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       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
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       to man-pages@man7.org

systemd 233                                                FILE-HIERARCHY(7)