FILE-HIERARCHY(7) file-hierarchy FILE-HIERARCHY(7)
file-hierarchy - File system hierarchy overview
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.
/
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).
/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].
/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.
/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).
/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.
/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.
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 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).
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.
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. │
└───────────────────┴───────────────────────────┘
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. │
└─────────────────────────┴───────────────────────────┘
systemd(1), hier(7), systemd-path(1), systemd-gpt-auto-generator(8),
sysctl.d(5), tmpfiles.d(5), pkg-config(1), systemd.unit(5)
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/
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2017-07-05. If you dis‐
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you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
systemd 234 FILE-HIERARCHY(7)
Pages that refer to this page: systemd-path(1), daemon(7), systemd.directives(7), systemd.index(7)