NAME | SYNOPSIS | DESCRIPTION | AUTOMATIC DEPENDENCIES | UNIT FILE LOAD PATH | [UNIT] SECTION OPTIONS | [INSTALL] SECTION OPTIONS | SPECIFIERS | EXAMPLES | SEE ALSO | NOTES | COLOPHON

SYSTEMD.UNIT(5)                 systemd.unit                 SYSTEMD.UNIT(5)

NAME         top

       systemd.unit - Unit configuration

SYNOPSIS         top

       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/*
       /usr/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         top

       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 and 200 milliseconds, i.e. 120200 ms. 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.

       Units can be aliased (have an alternative name), by creating a
       symlink from the new name to the existing name in one of the unit
       search paths. For example, systemd-networkd.service has the alias
       dbus-org.freedesktop.network1.service, created during installation as
       the symlink
       /usr/lib/systemd/system/dbus-org.freedesktop.network1.service. In
       addition, unit files may specify aliases through the Alias= directive
       in the [Install] section; those aliases are only effective when the
       unit is enabled. When the unit is enabled, symlinks will be created
       for those names, and removed when the unit is disabled. For example,
       reboot.target specifies Alias=ctrl-alt-del.target, so when enabled it
       will be invoked whenever CTRL+ALT+DEL is pressed. Alias names may be
       used in commands like enable, disable, start, stop, status, ..., and
       in unit dependency directives Wants=, Requires=, Before=, After=,
       ..., with the limitation that aliases specified through Alias= are
       only effective when the unit is enabled. Aliases cannot be used with
       the preset command.

       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 honored in drop-in unit files, and have no effect.

       In addition to /etc/systemd/system, the drop-in ".d" directories for
       system services can be placed in /usr/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 /usr/lib. Drop-in files under any of these directories take
       precedence over unit files wherever located. Multiple drop-in files
       with different names are applied in lexicographic order, regardless
       of which of the directories they reside in.

       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         top

       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         top

       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.

       Table 1.  Load path when running in system mode (--system).
       ┌────────────────────────┬─────────────────────┐
       │Path                    Description         │
       ├────────────────────────┼─────────────────────┤
       │/etc/systemd/system     │ Local configuration │
       ├────────────────────────┼─────────────────────┤
       │/run/systemd/system     │ Runtime units       │
       ├────────────────────────┼─────────────────────┤
       │/usr/lib/systemd/system │ Units of installed  │
       │                        │ packages            │
       └────────────────────────┴─────────────────────┘

       Table 2.  Load path when running in user mode (--user).
       ┌────────────────────────────────┬──────────────────────────┐
       │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              │
       └────────────────────────────────┴──────────────────────────┘

       Additional units might be loaded into systemd ("linked") from
       directories not on the unit load path. See the link command for
       systemctl(1). Also, some units are dynamically created via a
       systemd.generator(7).

[UNIT] SECTION OPTIONS         top

       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 this dependency type does not imply that the other unit
           always has to be in active state when this unit is running.
           Specifically: failing condition checks (such as
           ConditionPathExists=, ConditionPathExists=, ... — see below) do
           not cause the start job of a unit with a Requires= dependency on
           it to fail. Also, some unit types may deactivate on their own
           (for example, a service process may decide to exit cleanly, or a
           device may be unplugged by the user), which is not propagated to
           units having a Requires= dependency. Use the BindsTo= dependency
           type together with After= to ensure that a unit may never be in
           active state without a specific other unit also in active state
           (see below).

           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, this dependency type is stronger: in addition
           to the effect of Requires= it declares that if the unit bound to
           is stopped, this unit will be stopped too. This means a unit
           bound to another unit that suddenly enters inactive state will be
           stopped too. Units can suddenly, unexpectedly enter inactive
           state for different reasons: the main process of a service unit
           might terminate on its own choice, the backing device of a device
           unit might be unplugged or the mount point of a mount unit might
           be unmounted without involvement of the system and service
           manager.

           When used in conjunction with After= on the same unit the
           behaviour of BindsTo= is even stronger. In this case, the unit
           bound to strictly has to be in active state for this unit to also
           be in active state. This not only means a unit bound to another
           unit that suddenly enters inactive state, but also one that is
           bound to another unit that gets skipped due to a failed condition
           check (such as ConditionPathExists=,
           ConditionPathIsSymbolicLink=, ... — see below) will be stopped,
           should it be running. Hence, in many cases it is best to combine
           BindsTo= with After=.

       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=
           These two settings expect a space-separated list of unit names.
           They configure 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 has finished starting up. Note that this setting is
           independent of and orthogonal to the requirement dependencies as
           configured by Requires=, Wants= or BindsTo=. It is a common
           pattern to include a unit name in both the After= and Requires=
           options, 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, 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=,
           in this case. 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.
           It depends on the unit type when precisely a unit has finished
           starting up. Most importantly, for service units start-up is
           considered completed for the purpose of Before=/After= when all
           its configured start-up commands have been invoked and they
           either failed or reported start-up success.

       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
           through local-fs.target, but are still honored for the purposes
           of this option, i.e. they will be pulled in by this unit.

       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=, JobRunningTimeoutSec=, JobTimeoutAction=,
       JobTimeoutRebootArgument=
           When a job for this unit is queued, a time-out JobTimeoutSec= may
           be configured. Similarly, JobRunningTimeoutSec= starts counting
           when the queued job is actually started. If either 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
           (JobRunningTimeoutSec= defaults to DefaultTimeoutStartSec=). 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=, ConditionUser=, ConditionGroup=
           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, m68k, tilegx, cris, arc,
           arc-be 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, or private-users to check whether we are running
           in a user namespace. 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 (specifically: an /etc with
           no /etc/machine-id). This may be used to populate /etc on the
           first boot after factory reset, or when a new system instance
           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.

           ConditionUser= takes a numeric "UID", a UNIX user name, or the
           special value "@system". This condition may be used to check
           whether the service manager is running as the given user. The
           special value "@system" can be used to check if the user id is
           within the system user range. This option is not useful for
           system services, as the system manager exclusively runs as the
           root user, and thus the test result is constant.

           ConditionGroup= is similar to ConditionUser= but verifies that
           the service manager's real or effective group, or any of its
           auxiliary groups match the specified group or GID. This setting
           does not have a special value "@system".

           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=, AssertUser=,
       AssertGroup=
           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         top

       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         top

       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:

       Table 3. Specifiers available in unit files
       ┌──────────┬─────────────────────┬─────────────────────┐
       │Specifier Meaning             Details             │
       ├──────────┼─────────────────────┼─────────────────────┤
       │"%n"      │ Full unit name      │                     │
       ├──────────┼─────────────────────┼─────────────────────┤
       │"%N"      │ Unescaped full unit │ Same as "%n", but   │
       │          │ name                │ 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    │ Same as "%p", but   │
       │          │ name                │ 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  │ Same as "%i", but   │
       │          │ name                │ with escaping       │
       │          │                     │ undone              │
       ├──────────┼─────────────────────┼─────────────────────┤
       │"%f"      │ Unescaped filename  │ This is either the  │
       │          │                     │ unescaped instance  │
       │          │                     │ name (if            │
       │          │                     │ applicable) with /  │
       │          │                     │ prepended (if       │
       │          │                     │ applicable), or the │
       │          │                     │ unescaped prefix    │
       │          │                     │ name prepended with │
       │          │                     │ /.                  │
       ├──────────┼─────────────────────┼─────────────────────┤
       │"%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         top

       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

       After running systemctl enable, a symlink
       /etc/systemd/system/multi-user.target.wants/foo.service linking to
       the actual unit will be created. It tells systemd to pull in the unit
       when starting multi-user.target. The inverse systemctl disable will
       remove that symlink again.

       Example 2. Overriding vendor settings

       There are two methods of overriding vendor settings in unit files:
       copying the unit file from /usr/lib/systemd/system to
       /etc/systemd/system and modifying the chosen settings. Alternatively,
       one can create a directory named unit.d/ within /etc/systemd/system
       and place a drop-in file name.conf there that only changes the
       specific settings one is interested in. Note that multiple such
       drop-in files are read if present, processed in lexicographic order
       of their filename.

       The advantage of the first method is that one easily overrides the
       complete unit, the vendor unit is not parsed at all anymore. It has
       the disadvantage that improvements to the unit file by the vendor are
       not automatically incorporated on updates.

       The advantage of the second method is that one only overrides the
       settings one specifically wants, where updates to the unit by the
       vendor automatically apply. This has the disadvantage that some
       future updates by the vendor might be incompatible with the local
       changes.

       Note that for drop-in files, if one wants to remove entries from a
       setting that is parsed as a list (and is not a dependency), such as
       ConditionPathExists= (or e.g.  ExecStart= in service units), one
       needs to first clear the list before re-adding all entries except the
       one that is to be removed. See below for an example.

       This also applies for user instances of systemd, but with different
       locations for the unit files. See the section on unit load paths for
       further details.

       Suppose there is a vendor-supplied unit
       /usr/lib/systemd/system/httpd.service with the following contents:

           [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

       Now one wants to change some settings as an administrator: firstly,
       in the local setup, /srv/webserver might not exist, because the HTTP
       server is configured to use /srv/www instead. Secondly, the local
       configuration makes the HTTP server also depend on a memory cache
       service, memcached.service, that should be pulled in (Requires=) and
       also be ordered appropriately (After=). Thirdly, in order to harden
       the service a bit more, the administrator would like to set the
       PrivateTmp= setting (see systemd.exec(5) for details). And lastly,
       the administrator would like to reset the niceness of the service to
       its default value of 0.

       The first possibility is to copy the unit file to
       /etc/systemd/system/httpd.service and change the chosen settings:

           [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

       Alternatively, the administrator could create a drop-in file
       /etc/systemd/system/httpd.service.d/local.conf with the following
       contents:

           [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

       Note that dependencies (After=, etc.) cannot be reset to an empty
       list, so dependencies can only be added in drop-ins. If you want to
       remove dependencies, you have to override the entire unit.

SEE ALSO         top

       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         top

        1. XDG Desktop Entry Specification
           http://standards.freedesktop.org/desktop-entry-spec/latest/

        2. Interface Stability Promise
           https://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise

COLOPHON         top

       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 2017-09-15.  If you dis‐
       cover any rendering problems in this HTML version of the page, or you
       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
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 234                                                  SYSTEMD.UNIT(5)

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