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SYSTEMD.UNIT(5) | systemd.unit | SYSTEMD.UNIT(5) |
NAME¶
systemd.unit - Unit configurationSYNOPSIS¶
service.service, socket.socket, device.device, mount.mount, automount.automount, swap.swap, target.target, path.path, timer.timer, slice.slice, scope.scope/etc/systemd/system/* /run/systemd/system/* /lib/systemd/system/* ...
~/.config/systemd/user/* /etc/systemd/user/* $XDG_RUNTIME_DIR/systemd/user/* /run/systemd/user/* ~/.local/share/systemd/user/* /usr/lib/systemd/user/* ...
DESCRIPTION¶
A unit configuration file encodes information about a service, a socket, a device, a mount point, an automount point, a swap file or partition, a start-up target, a watched file system path, a timer controlled and supervised by systemd(1), a resource management slice or a group of externally created processes. The syntax is inspired by XDG Desktop Entry Specification[1].desktop files, which are in turn inspired by Microsoft Windows .ini files. This man page lists the common configuration options of all the unit types. These options need to be configured in the [Unit] or [Install] sections of the unit files. In addition to the generic [Unit] and [Install] sections described here, each unit may have a type-specific section, e.g. [Service] for a service unit. See the respective man pages for more information: systemd.service(5), systemd.socket(5), systemd.device(5), systemd.mount(5), systemd.automount(5), systemd.swap(5), systemd.target(5), systemd.path(5), systemd.timer(5), systemd.slice(5), systemd.scope(5). Various settings are allowed to be specified more than once, in which case the interpretation depends on the setting. Often, multiple settings form a list, and setting to an empty value "resets", which means that previous assignments are ignored. When this is allowed, it is mentioned in the description of the setting. Note that using multiple assignments to the same value makes the unit file incompatible with parsers for the XDG .desktop file format. Unit files are loaded from a set of paths determined during compilation, described in the next section. Unit files may contain additional options on top of those listed here. If systemd encounters an unknown option, it will write a warning log message but continue loading the unit. If an option or section name is prefixed with X-, it is ignored completely by systemd. Options within an ignored section do not need the prefix. Applications may use this to include additional information in the unit files. Boolean arguments used in unit files can be written in various formats. For positive settings the strings 1, yes, true and on are equivalent. For negative settings, the strings 0, no, false and off are equivalent. Time span values encoded in unit files can be written in various formats. A stand-alone number specifies a time in seconds. If suffixed with a time unit, the unit is honored. A concatenation of multiple values with units is supported, in which case the values are added up. Example: "50" refers to 50 seconds; "2min 200ms" refers to 2 minutes plus 200 milliseconds, i.e. 120200ms. The following time units are understood: s, min, h, d, w, ms, us. For details see systemd.time(7). Empty lines and lines starting with # or ; are ignored. This may be used for commenting. Lines ending in a backslash are concatenated with the following line while reading and the backslash is replaced by a space character. This may be used to wrap long lines. Along with a unit file foo.service, the directory foo.service.wants/ may exist. All unit files symlinked from such a directory are implicitly added as dependencies of type Wants= to the unit. This is useful to hook units into the start-up of other units, without having to modify their unit files. For details about the semantics of Wants=, see below. The preferred way to create symlinks in the .wants/ directory of a unit file is with the enable command of the systemctl(1) tool which reads information from the [Install] section of unit files (see below). A similar functionality exists for Requires= type dependencies as well, the directory suffix is .requires/ in this case. Along with a unit file foo.service, a "drop-in" directory foo.service.d/ may exist. All files with the suffix ".conf" from this directory will be parsed after the file itself is parsed. This is useful to alter or add configuration settings for a unit, without having to modify unit files. Each drop-in file must have appropriate section headers. Note that for instantiated units, this logic will first look for the instance ".d/" subdirectory and read its ".conf" files, followed by the template ".d/" subdirectory and the ".conf" files there. Also note that settings from the "[Install]" section are not honoured in drop-in unit files, and have no effect. In addition to /etc/systemd/system, the drop-in ".conf" files for system services can be placed in /lib/systemd/system or /run/systemd/system directories. Drop-in files in /etc take precedence over those in /run which in turn take precedence over those in /lib. Drop-in files under any of these directories take precedence over unit files wherever located. (Of course, since /run is temporary and /usr/lib is for vendors, it is unlikely drop-ins should be used in either of those places.) Some unit names reflect paths existing in the file system namespace. Example: a device unit dev-sda.device refers to a device with the device node /dev/sda in the file system namespace. If this applies, a special way to escape the path name is used, so that the result is usable as part of a filename. Basically, given a path, "/" is replaced by "-", and all other characters which are not ASCII alphanumerics are replaced by C-style "\x2d" escapes (except that "_" is never replaced and "." is only replaced when it would be the first character in the escaped path). The root directory "/" is encoded as single dash, while otherwise the initial and ending "/" are removed from all paths during transformation. This escaping is reversible. Properly escaped paths can be generated using the systemd-escape(1) command. Optionally, units may be instantiated from a template file at runtime. This allows creation of multiple units from a single configuration file. If systemd looks for a unit configuration file, it will first search for the literal unit name in the file system. If that yields no success and the unit name contains an "@" character, systemd will look for a unit template that shares the same name but with the instance string (i.e. the part between the "@" character and the suffix) removed. Example: if a service getty@tty3.service is requested and no file by that name is found, systemd will look for getty@.service and instantiate a service from that configuration file if it is found. To refer to the instance string from within the configuration file you may use the special "%i" specifier in many of the configuration options. See below for details. If a unit file is empty (i.e. has the file size 0) or is symlinked to /dev/null, its configuration will not be loaded and it appears with a load state of "masked", and cannot be activated. Use this as an effective way to fully disable a unit, making it impossible to start it even manually. The unit file format is covered by the Interface Stability Promise[2].AUTOMATIC DEPENDENCIES¶
Note that while systemd offers a flexible dependency system between units it is recommended to use this functionality only sparingly and instead rely on techniques such as bus-based or socket-based activation which make dependencies implicit, resulting in a both simpler and more flexible system. A number of unit dependencies are automatically established, depending on unit configuration. On top of that, for units with DefaultDependencies=yes (the default) a couple of additional dependencies are added. The precise effect of DefaultDependencies=yes depends on the unit type (see below). If DefaultDependencies=yes is set, units that are referenced by other units of type .target via a Wants= or Requires= dependency might automatically gain an Before= dependency too. See systemd.target(5) for details.UNIT FILE LOAD PATH¶
Unit files are loaded from a set of paths determined during compilation, described in the two tables below. Unit files found in directories listed earlier override files with the same name in directories lower in the list. When the variable $SYSTEMD_UNIT_PATH is set, the contents of this variable overrides the unit load path. If $SYSTEMD_UNIT_PATH ends with an empty component (":"), the usual unit load path will be appended to the contents of the variable.Path | Description |
/etc/systemd/system | Local configuration |
/run/systemd/system | Runtime units |
/lib/systemd/system | Units of installed packages |
Path | Description |
$XDG_CONFIG_HOME/systemd/user | User configuration (only used when $XDG_CONFIG_HOME is set) |
$HOME/.config/systemd/user | User configuration (only used when $XDG_CONFIG_HOME is not set) |
/etc/systemd/user | Local configuration |
$XDG_RUNTIME_DIR/systemd/user | Runtime units (only used when $XDG_RUNTIME_DIR is set) |
/run/systemd/user | Runtime units |
$XDG_DATA_HOME/systemd/user | Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is set) |
$HOME/.local/share/systemd/user | Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is not set) |
/usr/lib/systemd/user | Units of packages that have been installed system-wide |
[UNIT] SECTION OPTIONS¶
The unit file may include a [Unit] section, which carries generic information about the unit that is not dependent on the type of unit: Description=A free-form string describing the unit. This is intended
for use in UIs to show descriptive information along with the unit name. The
description should contain a name that means something to the end user.
"Apache2 Web Server" is a good example. Bad examples are
"high-performance light-weight HTTP server" (too generic) or
"Apache2" (too specific and meaningless for people who do not know
Apache).
Documentation=
A space-separated list of URIs referencing documentation
for this unit or its configuration. Accepted are only URIs of the types
"http://", "https://", "file:",
"info:", "man:". For more information about the syntax of
these URIs, see uri(7). The URIs should be listed in order of
relevance, starting with the most relevant. It is a good idea to first
reference documentation that explains what the unit's purpose is, followed by
how it is configured, followed by any other related documentation. This option
may be specified more than once, in which case the specified list of URIs is
merged. If the empty string is assigned to this option, the list is reset and
all prior assignments will have no effect.
Requires=
Configures requirement dependencies on other units. If
this unit gets activated, the units listed here will be activated as well. If
one of the other units gets deactivated or its activation fails, this unit
will be deactivated. This option may be specified more than once or multiple
space-separated units may be specified in one option in which case requirement
dependencies for all listed names will be created. Note that requirement
dependencies do not influence the order in which services are started or
stopped. This has to be configured independently with the After= or
Before= options. If a unit foo.service requires a unit bar.service as
configured with Requires= and no ordering is configured with
After= or Before=, then both units will be started
simultaneously and without any delay between them if foo.service is activated.
Often, it is a better choice to use Wants= instead of Requires=
in order to achieve a system that is more robust when dealing with failing
services.
Note that dependencies of this type may also be configured outside of the unit
configuration file by adding a symlink to a .requires/ directory accompanying
the unit file. For details, see above.
Requisite=
Similar to Requires=. However, if the units listed
here are not started already, they will not be started and the transaction
will fail immediately.
Wants=
A weaker version of Requires=. Units listed in
this option will be started if the configuring unit is. However, if the listed
units fail to start or cannot be added to the transaction, this has no impact
on the validity of the transaction as a whole. This is the recommended way to
hook start-up of one unit to the start-up of another unit.
Note that dependencies of this type may also be configured outside of the unit
configuration file by adding symlinks to a .wants/ directory accompanying the
unit file. For details, see above.
BindsTo=
Configures requirement dependencies, very similar in
style to Requires=, however in addition to this behavior, it also
declares that this unit is stopped when any of the units listed suddenly
disappears. Units can suddenly, unexpectedly disappear if a service terminates
on its own choice, a device is unplugged or a mount point unmounted without
involvement of systemd.
PartOf=
Configures dependencies similar to Requires=, but
limited to stopping and restarting of units. When systemd stops or restarts
the units listed here, the action is propagated to this unit. Note that this
is a one-way dependency — changes to this unit do not affect the
listed units.
Conflicts=
A space-separated list of unit names. Configures negative
requirement dependencies. If a unit has a Conflicts= setting on another
unit, starting the former will stop the latter and vice versa. Note that this
setting is independent of and orthogonal to the After= and
Before= ordering dependencies.
If a unit A that conflicts with a unit B is scheduled to be started at the same
time as B, the transaction will either fail (in case both are required part of
the transaction) or be modified to be fixed (in case one or both jobs are not
a required part of the transaction). In the latter case, the job that is not
the required will be removed, or in case both are not required, the unit that
conflicts will be started and the unit that is conflicted is stopped.
Before=, After=
A space-separated list of unit names. Configures ordering
dependencies between units. If a unit foo.service contains a setting
Before=bar.service and both units are being started, bar.service's
start-up is delayed until foo.service is started up. Note that this setting is
independent of and orthogonal to the requirement dependencies as configured by
Requires=. It is a common pattern to include a unit name in both the
After= and Requires= option, in which case the unit listed will
be started before the unit that is configured with these options. This option
may be specified more than once, in which case ordering dependencies for all
listed names are created. After= is the inverse of Before=, i.e.
while After= ensures that the configured unit is started after the
listed unit finished starting up, Before= ensures the opposite, i.e.
that the configured unit is fully started up before the listed unit is
started. Note that when two units with an ordering dependency between them are
shut down, the inverse of the start-up order is applied. i.e. if a unit is
configured with After= on another unit, the former is stopped before
the latter if both are shut down. Given two units with any ordering dependency
between them, if one unit is shut down and the other is started up, the
shutdown is ordered before the start-up. It doesn't matter if the ordering
dependency is After= or Before=. It also doesn't matter which of
the two is shut down, as long as one is shut down and the other is started up.
The shutdown is ordered before the start-up in all cases. If two units have no
ordering dependencies between them, they are shut down or started up
simultaneously, and no ordering takes place.
OnFailure=
A space-separated list of one or more units that are
activated when this unit enters the "failed" state.
PropagatesReloadTo=, ReloadPropagatedFrom=
A space-separated list of one or more units where reload
requests on this unit will be propagated to, or reload requests on the other
unit will be propagated to this unit, respectively. Issuing a reload request
on a unit will automatically also enqueue a reload request on all units that
the reload request shall be propagated to via these two settings.
JoinsNamespaceOf=
For units that start processes (such as service units),
lists one or more other units whose network and/or temporary file namespace to
join. This only applies to unit types which support the PrivateNetwork=
and PrivateTmp= directives (see systemd.exec(5) for details). If
a unit that has this setting set is started, its processes will see the same
/tmp, /var/tmp and network namespace as one listed unit that is started. If
multiple listed units are already started, it is not defined which namespace
is joined. Note that this setting only has an effect if PrivateNetwork=
and/or PrivateTmp= is enabled for both the unit that joins the
namespace and the unit whose namespace is joined.
RequiresMountsFor=
Takes a space-separated list of absolute paths.
Automatically adds dependencies of type Requires= and After= for
all mount units required to access the specified path.
Mount points marked with noauto are not mounted automatically and will be
ignored for the purposes of this option. If such a mount should be a
requirement for this unit, direct dependencies on the mount units may be added
( Requires= and After= or some other combination).
OnFailureJobMode=
Takes a value of "fail", "replace",
"replace-irreversibly", "isolate", "flush",
"ignore-dependencies" or "ignore-requirements". Defaults
to "replace". Specifies how the units listed in OnFailure=
will be enqueued. See systemctl(1)'s --job-mode= option for
details on the possible values. If this is set to "isolate", only a
single unit may be listed in OnFailure=..
IgnoreOnIsolate=
Takes a boolean argument. If true, this unit will
not be stopped when isolating another unit. Defaults to false.
StopWhenUnneeded=
Takes a boolean argument. If true, this unit will
be stopped when it is no longer used. Note that, in order to minimize the work
to be executed, systemd will not stop units by default unless they are
conflicting with other units, or the user explicitly requested their shut
down. If this option is set, a unit will be automatically cleaned up if no
other active unit requires it. Defaults to false.
RefuseManualStart=, RefuseManualStop=
Takes a boolean argument. If true, this unit can
only be activated or deactivated indirectly. In this case, explicit start-up
or termination requested by the user is denied, however if it is started or
stopped as a dependency of another unit, start-up or termination will succeed.
This is mostly a safety feature to ensure that the user does not accidentally
activate units that are not intended to be activated explicitly, and not
accidentally deactivate units that are not intended to be deactivated. These
options default to false.
AllowIsolate=
Takes a boolean argument. If true, this unit may
be used with the systemctl isolate command. Otherwise, this will be
refused. It probably is a good idea to leave this disabled except for target
units that shall be used similar to runlevels in SysV init systems, just as a
precaution to avoid unusable system states. This option defaults to
false.
DefaultDependencies=
Takes a boolean argument. If true, (the default),
a few default dependencies will implicitly be created for the unit. The actual
dependencies created depend on the unit type. For example, for service units,
these dependencies ensure that the service is started only after basic system
initialization is completed and is properly terminated on system shutdown. See
the respective man pages for details. Generally, only services involved with
early boot or late shutdown should set this option to false. It is
highly recommended to leave this option enabled for the majority of common
units. If set to false, this option does not disable all implicit
dependencies, just non-essential ones.
JobTimeoutSec=, JobTimeoutAction=,
JobTimeoutRebootArgument=
When a job for this unit is queued, a time-out may be
configured. If this time limit is reached, the job will be cancelled, the unit
however will not change state or even enter the "failed" mode. This
value defaults to "infinity" (job timeouts disabled), except for
device units. NB: this timeout is independent from any unit-specific timeout
(for example, the timeout set with TimeoutStartSec= in service units)
as the job timeout has no effect on the unit itself, only on the job that
might be pending for it. Or in other words: unit-specific timeouts are useful
to abort unit state changes, and revert them. The job timeout set with this
option however is useful to abort only the job waiting for the unit state to
change.
JobTimeoutAction= optionally configures an additional action to take when
the time-out is hit. It takes the same values as the per-service
StartLimitAction= setting, see systemd.service(5) for details.
Defaults to none. JobTimeoutRebootArgument= configures an
optional reboot string to pass to the reboot(2) system call.
StartLimitIntervalSec=, StartLimitBurst=
Configure unit start rate limiting. By default, units
which are started more than 5 times within 10 seconds are not permitted to
start any more times until the 10 second interval ends. With these two
options, this rate limiting may be modified. Use StartLimitIntervalSec=
to configure the checking interval (defaults to
DefaultStartLimitIntervalSec= in manager configuration file, set to 0
to disable any kind of rate limiting). Use StartLimitBurst= to
configure how many starts per interval are allowed (defaults to
DefaultStartLimitBurst= in manager configuration file). These
configuration options are particularly useful in conjunction with the service
setting Restart= (see systemd.service(5)); however, they apply
to all kinds of starts (including manual), not just those triggered by the
Restart= logic. Note that units which are configured for
Restart= and which reach the start limit are not attempted to be
restarted anymore; however, they may still be restarted manually at a later
point, from which point on, the restart logic is again activated. Note that
systemctl reset-failed will cause the restart rate counter for a
service to be flushed, which is useful if the administrator wants to manually
start a unit and the start limit interferes with that. Note that this
rate-limiting is enforced after any unit condition checks are executed, and
hence unit activations with failing conditions are not counted by this rate
limiting. Slice, target, device and scope units do not enforce this setting,
as they are unit types whose activation may either never fail, or may succeed
only a single time.
StartLimitAction=
Configure the action to take if the rate limit configured
with StartLimitIntervalSec= and StartLimitBurst= is hit. Takes
one of none, reboot, reboot-force,
reboot-immediate, poweroff, poweroff-force or
poweroff-immediate. If none is set, hitting the rate limit will
trigger no action besides that the start will not be permitted. reboot
causes a reboot following the normal shutdown procedure (i.e. equivalent to
systemctl reboot). reboot-force causes a forced reboot which
will terminate all processes forcibly but should cause no dirty file systems
on reboot (i.e. equivalent to systemctl reboot -f) and
reboot-immediate causes immediate execution of the reboot(2)
system call, which might result in data loss. Similarly, poweroff,
poweroff-force, poweroff-immediate have the effect of powering
down the system with similar semantics. Defaults to none.
RebootArgument=
Configure the optional argument for the reboot(2)
system call if StartLimitAction= or a service's FailureAction=
is a reboot action. This works just like the optional argument to systemctl
reboot command.
ConditionArchitecture=, ConditionVirtualization=,
ConditionHost=, ConditionKernelCommandLine=,
ConditionSecurity=, ConditionCapability=,
ConditionACPower=, ConditionNeedsUpdate=,
ConditionFirstBoot=, ConditionPathExists=,
ConditionPathExistsGlob=, ConditionPathIsDirectory=,
ConditionPathIsSymbolicLink=, ConditionPathIsMountPoint=,
ConditionPathIsReadWrite=, ConditionDirectoryNotEmpty=,
ConditionFileNotEmpty=, ConditionFileIsExecutable=
Before starting a unit, verify that the specified
condition is true. If it is not true, the starting of the unit will be (mostly
silently) skipped, however all ordering dependencies of it are still
respected. A failing condition will not result in the unit being moved into a
failure state. The condition is checked at the time the queued start job is to
be executed. Use condition expressions in order to silently skip units that do
not apply to the local running system, for example because the kernel or
runtime environment doesn't require its functionality. Use the various
AssertArchitecture=, AssertVirtualization=, ... options for a
similar mechanism that puts the unit in a failure state and logs about the
failed check (see below).
ConditionArchitecture= may be used to check whether the system is running
on a specific architecture. Takes one of x86, x86-64,
ppc, ppc-le, ppc64, ppc64-le, ia64,
parisc, parisc64, s390, s390x, sparc,
sparc64, mips, mips-le, mips64, mips64-le,
alpha, arm, arm-be, arm64, arm64-be,
sh, sh64, m86k, tilegx, cris to test
against a specific architecture. The architecture is determined from the
information returned by uname(2) and is thus subject to
personality(2). Note that a Personality= setting in the same
unit file has no effect on this condition. A special architecture name
native is mapped to the architecture the system manager itself is
compiled for. The test may be negated by prepending an exclamation mark.
ConditionVirtualization= may be used to check whether the system is
executed in a virtualized environment and optionally test whether it is a
specific implementation. Takes either boolean value to check if being executed
in any virtualized environment, or one of vm and container to
test against a generic type of virtualization solution, or one of qemu,
kvm, zvm, vmware, microsoft, oracle,
xen, bochs, uml, openvz, lxc,
lxc-libvirt, systemd-nspawn, docker, rkt to test
against a specific implementation. See systemd-detect-virt(1) for a
full list of known virtualization technologies and their identifiers. If
multiple virtualization technologies are nested, only the innermost is
considered. The test may be negated by prepending an exclamation mark.
ConditionHost= may be used to match against the hostname or machine ID of
the host. This either takes a hostname string (optionally with shell style
globs) which is tested against the locally set hostname as returned by
gethostname(2), or a machine ID formatted as string (see
machine-id(5)). The test may be negated by prepending an exclamation
mark.
ConditionKernelCommandLine= may be used to check whether a specific
kernel command line option is set (or if prefixed with the exclamation mark
unset). The argument must either be a single word, or an assignment (i.e. two
words, separated "="). In the former case the kernel command line is
searched for the word appearing as is, or as left hand side of an assignment.
In the latter case, the exact assignment is looked for with right and left
hand side matching.
ConditionSecurity= may be used to check whether the given security module
is enabled on the system. Currently, the recognized values are selinux,
apparmor, ima, smack and audit. The test may be
negated by prepending an exclamation mark.
ConditionCapability= may be used to check whether the given capability
exists in the capability bounding set of the service manager (i.e. this does
not check whether capability is actually available in the permitted or
effective sets, see capabilities(7) for details). Pass a capability
name such as "CAP_MKNOD", possibly prefixed with an exclamation mark
to negate the check.
ConditionACPower= may be used to check whether the system has AC power,
or is exclusively battery powered at the time of activation of the unit. This
takes a boolean argument. If set to true, the condition will hold only
if at least one AC connector of the system is connected to a power source, or
if no AC connectors are known. Conversely, if set to false, the
condition will hold only if there is at least one AC connector known and all
AC connectors are disconnected from a power source.
ConditionNeedsUpdate= takes one of /var or /etc as argument, possibly
prefixed with a "!" (for inverting the condition). This condition
may be used to conditionalize units on whether the specified directory
requires an update because /usr's modification time is newer than the stamp
file .updated in the specified directory. This is useful to implement offline
updates of the vendor operating system resources in /usr that require updating
of /etc or /var on the next following boot. Units making use of this condition
should order themselves before systemd-update-done.service(8), to make
sure they run before the stamp file's modification time gets reset indicating
a completed update.
ConditionFirstBoot= takes a boolean argument. This condition may be used
to conditionalize units on whether the system is booting up with an
unpopulated /etc directory. This may be used to populate /etc on the first
boot after factory reset, or when a new system instances boots up for the
first time.
With ConditionPathExists= a file existence condition is checked before a
unit is started. If the specified absolute path name does not exist, the
condition will fail. If the absolute path name passed to
ConditionPathExists= is prefixed with an exclamation mark
("!"), the test is negated, and the unit is only started if the path
does not exist.
ConditionPathExistsGlob= is similar to ConditionPathExists=, but
checks for the existence of at least one file or directory matching the
specified globbing pattern.
ConditionPathIsDirectory= is similar to ConditionPathExists= but
verifies whether a certain path exists and is a directory.
ConditionPathIsSymbolicLink= is similar to ConditionPathExists=
but verifies whether a certain path exists and is a symbolic link.
ConditionPathIsMountPoint= is similar to ConditionPathExists= but
verifies whether a certain path exists and is a mount point.
ConditionPathIsReadWrite= is similar to ConditionPathExists= but
verifies whether the underlying file system is readable and writable (i.e. not
mounted read-only).
ConditionDirectoryNotEmpty= is similar to ConditionPathExists= but
verifies whether a certain path exists and is a non-empty directory.
ConditionFileNotEmpty= is similar to ConditionPathExists= but
verifies whether a certain path exists and refers to a regular file with a
non-zero size.
ConditionFileIsExecutable= is similar to ConditionPathExists= but
verifies whether a certain path exists, is a regular file and marked
executable.
If multiple conditions are specified, the unit will be executed if all of them
apply (i.e. a logical AND is applied). Condition checks can be prefixed with a
pipe symbol (|) in which case a condition becomes a triggering condition. If
at least one triggering condition is defined for a unit, then the unit will be
executed if at least one of the triggering conditions apply and all of the
non-triggering conditions. If you prefix an argument with the pipe symbol and
an exclamation mark, the pipe symbol must be passed first, the exclamation
second. Except for ConditionPathIsSymbolicLink=, all path checks follow
symlinks. If any of these options is assigned the empty string, the list of
conditions is reset completely, all previous condition settings (of any kind)
will have no effect.
AssertArchitecture=, AssertVirtualization=, AssertHost=,
AssertKernelCommandLine=, AssertSecurity=,
AssertCapability=, AssertACPower=, AssertNeedsUpdate=,
AssertFirstBoot=, AssertPathExists=,
AssertPathExistsGlob=, AssertPathIsDirectory=,
AssertPathIsSymbolicLink=, AssertPathIsMountPoint=,
AssertPathIsReadWrite=, AssertDirectoryNotEmpty=,
AssertFileNotEmpty=, AssertFileIsExecutable=
Similar to the ConditionArchitecture=,
ConditionVirtualization=, ..., condition settings described above,
these settings add assertion checks to the start-up of the unit. However,
unlike the conditions settings, any assertion setting that is not met results
in failure of the start job (which means this is logged loudly). Use assertion
expressions for units that cannot operate when specific requirements are not
met, and when this is something the administrator or user should look
into.
SourcePath=
A path to a configuration file this unit has been
generated from. This is primarily useful for implementation of generator tools
that convert configuration from an external configuration file format into
native unit files. This functionality should not be used in normal
units.
[INSTALL] SECTION OPTIONS¶
Unit files may include an "[Install]" section, which carries installation information for the unit. This section is not interpreted by systemd(1) during runtime; it is used by the enable and disable commands of the systemctl(1) tool during installation of a unit. Note that settings in the "[Install]" section may not appear in .d/*.conf unit file drop-ins (see above). Alias=A space-separated list of additional names this unit
shall be installed under. The names listed here must have the same suffix
(i.e. type) as the unit file name. This option may be specified more than
once, in which case all listed names are used. At installation time,
systemctl enable will create symlinks from these names to the unit
filename. Note that not all unit types support such alias names, and this
setting is not supported for them. Specifically, mount, slice, swap, and
automount units do not support aliasing.
WantedBy=, RequiredBy=
This option may be used more than once, or a
space-separated list of unit names may be given. A symbolic link is created in
the .wants/ or .requires/ directory of each of the listed units when this unit
is installed by systemctl enable. This has the effect that a dependency
of type Wants= or Requires= is added from the listed unit to the
current unit. The primary result is that the current unit will be started when
the listed unit is started. See the description of Wants= and
Requires= in the [Unit] section for details.
WantedBy=foo.service in a service bar.service is mostly equivalent to
Alias=foo.service.wants/bar.service in the same file. In case of
template units, systemctl enable must be called with an instance name,
and this instance will be added to the .wants/ or .requires/ list of the
listed unit. E.g. WantedBy=getty.target in a service getty@.service
will result in systemctl enable getty@tty2.service creating a
getty.target.wants/getty@tty2.service link to getty@.service.
Also=
Additional units to install/deinstall when this unit is
installed/deinstalled. If the user requests installation/deinstallation of a
unit with this option configured, systemctl enable and systemctl
disable will automatically install/uninstall units listed in this option
as well.
This option may be used more than once, or a space-separated list of unit names
may be given.
DefaultInstance=
In template unit files, this specifies for which instance
the unit shall be enabled if the template is enabled without any explicitly
set instance. This option has no effect in non-template unit files. The
specified string must be usable as instance identifier.
The following specifiers are interpreted in the Install section: %n, %N, %p, %i,
%U, %u, %m, %H, %b, %v. For their meaning see the next section.
SPECIFIERS¶
Many settings resolve specifiers which may be used to write generic unit files referring to runtime or unit parameters that are replaced when the unit files are loaded. The following specifiers are understood:Specifier | Meaning | Details |
"%n" | Full unit name | |
"%N" | Unescaped full unit name | Same as "%n", but with escaping undone |
"%p" | Prefix name | For instantiated units, this refers to the string before the "@" character of the unit name. For non-instantiated units, this refers to the name of the unit with the type suffix removed. |
"%P" | Unescaped prefix name | Same as "%p", but with escaping undone |
"%i" | Instance name | For instantiated units: this is the string between the "@" character and the suffix of the unit name. |
"%I" | Unescaped instance name | Same as "%i", but with escaping undone |
"%f" | Unescaped filename | This is either the unescaped instance name (if applicable) with / prepended (if applicable), or the prefix name prepended with /. |
"%c" | Control group path of the unit | This path does not include the /sys/fs/cgroup/systemd/ prefix. |
"%r" | Control group path of the slice the unit is placed in | This usually maps to the parent cgroup path of "%c". |
"%R" | Root control group path below which slices and units are placed | For system instances, this resolves to /, except in containers, where this maps to the container's root control group path. |
"%t" | Runtime directory | This is either /run (for the system manager) or the path "$XDG_RUNTIME_DIR" resolves to (for user managers). |
"%u" | User name | This is the name of the user running the service manager instance. In case of the system manager this resolves to "root". |
"%U" | User UID | This is the numeric UID of the user running the service manager instance. In case of the system manager this resolves to "0". |
"%h" | User home directory | This is the home directory of the user running the service manager instance. In case of the system manager this resolves to "/root". |
"%s" | User shell | This is the shell of the user running the service manager instance. In case of the system manager this resolves to "/bin/sh". |
"%m" | Machine ID | The machine ID of the running system, formatted as string. See machine-id(5) for more information. |
"%b" | Boot ID | The boot ID of the running system, formatted as string. See random(4) for more information. |
"%H" | Host name | The hostname of the running system at the point in time the unit configuration is loaded. |
"%v" | Kernel release | Identical to uname -r output |
"%%" | Single percent sign | Use "%%" in place of "%" to specify a single percent sign. |
EXAMPLES¶
Example 1. Allowing units to be enabled The following snippet (highlighted) allows a unit (e.g. foo.service) to be enabled via systemctl enable:[Unit] Description=Foo [Service] ExecStart=/usr/sbin/foo-daemon [Install] WantedBy=multi-user.target
[Unit] Description=Some HTTP server After=remote-fs.target sqldb.service Requires=sqldb.service AssertPathExists=/srv/webserver [Service] Type=notify ExecStart=/usr/sbin/some-fancy-httpd-server Nice=5 [Install] WantedBy=multi-user.target
[Unit] Description=Some HTTP server After=remote-fs.target sqldb.service memcached.service Requires=sqldb.service memcached.service AssertPathExists= /srv/www [Service] Type=notify ExecStart=/usr/sbin/some-fancy-httpd-server Nice=0 PrivateTmp=yes [Install] WantedBy=multi-user.target
[Unit] After=memcached.service Requires=memcached.service # Reset all assertions and then re-add the condition we want AssertPathExists= AssertPathExists=/srv/www [Service] Nice=0 PrivateTmp=yes
SEE ALSO¶
systemd(1), systemctl(1), systemd.special(7), systemd.service(5), systemd.socket(5), systemd.device(5), systemd.mount(5), systemd.automount(5), systemd.swap(5), systemd.target(5), systemd.path(5), systemd.timer(5), systemd.scope(5), systemd.slice(5), systemd.time(7), systemd-analyze(1), capabilities(7), systemd.directives(7), uname(1)NOTES¶
- 1.
- XDG Desktop Entry Specification
- 2.
- Interface Stability Promise
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