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



NAME
       file-hierarchy - File system hierarchy overview

DESCRIPTION
       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 are queriable with the systemd-path(1) tool.

GENERAL STRUCTURE
       /
           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-efi-boot-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).

           directly, but via the $XDG_RUNTIME_DIR environment variable, as documented in the XDG Base Directory
           Specification[3].

VENDOR-SUPPLIED OPERATING SYSTEM RESOURCES
       /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, 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:

               # pkg-config --variable=libdir
                       systemd

           or

               # 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
           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
       /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 those 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.
           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
       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 is 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 is 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 is should use the directory specified in it instead of this
           directory.

UNPRIVILEGED WRITE ACCESS
       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
       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
       ┌───────────────────┬─────────────────────────────────────────┐
       │/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
       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.)
       │                             │ 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
       systemd(1), hier(7), systemd-path(1), systemd-efi-boot-generator(8), sysctl.d(5), tmpfiles.d(5), pkg-
       config(1), systemd.unit(5)

NOTES

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



systemd 219                                                                                         FILE-HIERARCHY(7)