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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)
systemd.unit - Unit configuration
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/*
...
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].
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 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).
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.
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.
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. │
└──────────┴─────────────────────┴─────────────────────┘
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.
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)
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
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2017-07-05. If you dis‐
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)
Pages that refer to this page: systemctl(1), systemd(1), systemd-analyze(1), systemd-delta(1), systemd-firstboot(1), systemd-mount(1), systemd-notify(1), systemd-run(1), sd_bus_creds_get_pid(3), systemd.automount(5), systemd.device(5), systemd.exec(5), systemd.kill(5), systemd.link(5), systemd.mount(5), systemd.netdev(5), systemd.network(5), systemd.path(5), systemd.preset(5), systemd.resource-control(5), systemd.scope(5), systemd.service(5), systemd.slice(5), systemd.socket(5), systemd.swap(5), systemd.target(5), systemd.timer(5), daemon(7), file-hierarchy(7), nfs.systemd(7), systemd.directives(7), systemd.generator(7), systemd.index(7), systemd.special(7), systemd.time(7), systemd-update-done.service(8)