NAME
systemd.unit - Unit configurationSYNOPSIS
service.service, socket.socket, device.device, mount.mount, automount.automount, swap.swap, target.target, path.path, timer.timer, slice.slice, scope.scopeSystem Unit Search Path
/etc/systemd/system.control/* /run/systemd/system.control/* /run/systemd/transient/* /run/systemd/generator.early/* /etc/systemd/system/* /etc/systemd/system.attached/* /run/systemd/system/* /run/systemd/system.attached/* /run/systemd/generator/* ... /lib/systemd/system/* /run/systemd/generator.late/*
User Unit Search Path
~/.config/systemd/user.control/* $XDG_RUNTIME_DIR/systemd/user.control/* $XDG_RUNTIME_DIR/systemd/transient/* $XDG_RUNTIME_DIR/systemd/generator.early/* ~/.config/systemd/user/* $XDG_CONFIG_DIRS/systemd/user/* /etc/systemd/user/* $XDG_RUNTIME_DIR/systemd/user/* /run/systemd/user/* $XDG_RUNTIME_DIR/systemd/generator/* $XDG_DATA_HOME/systemd/user/* $XDG_DATA_DIRS/systemd/user/* ... /usr/lib/systemd/user/* $XDG_RUNTIME_DIR/systemd/generator.late/*
DESCRIPTION
A unit file is a plain text ini-style file that 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. See systemd.syntax(7) for a general description of the syntax. 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). Unit files are loaded from a set of paths determined during compilation, described in the next section. Valid unit names consist of a "unit name prefix", and a suffix specifying the unit type which begins with a dot. The "unit name prefix" must consist of one or more valid characters (ASCII letters, digits, ":", "-", "_", ".", and "\"). The total length of the unit name including the suffix must not exceed 255 characters. The unit type suffix must be one of ".service", ".socket", ".device", ".mount", ".automount", ".swap", ".target", ".path", ".timer", ".slice", or ".scope". Unit names can be parameterized by a single argument called the "instance name". The unit is then constructed based on a "template file" which serves as the definition of multiple services or other units. A template unit must have a single "@" at the end of the unit name prefix (right before the type suffix). The name of the full unit is formed by inserting the instance name between "@" and the unit type suffix. In the unit file itself, the instance parameter may be referred to using "%i" and other specifiers, see below. 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. To access those options, applications need to parse the unit files on their own. 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 a symlink, so when systemd is asked through D-Bus to load dbus-org.freedesktop.network1.service, it'll load systemd-networkd.service. As another example, default.target — the default system target started at boot — is commonly aliased to either multi-user.target or graphical.target to select what is started by default. Alias names may be used in commands like disable, start, stop, status, and similar, and in all unit dependency directives, including Wants=, Requires=, Before=, After=. Aliases cannot be used with the preset command. Aliases obey the following restrictions: a unit of a certain type (".service", ".socket", ...) can only be aliased by a name with the same type suffix. A plain unit (not a template or an instance), may only be aliased by a plain name. A template instance may only be aliased by another template instance, and the instance part must be identical. A template may be aliased by another template (in which case the alias applies to all instances of the template). As a special case, a template instance (e.g. "[email protected]") may be a symlink to different template (e.g. "[email protected]"). In that case, just this specific instance is aliased, while other instances of the template (e.g. "[email protected]", "[email protected]") are not aliased. Those rules preserve the requirement that the instance (if any) is always uniquely defined for a given unit and all its aliases. The target of alias symlink must point to a valid unit file location, i.e. the symlink target name must match the symlink source name as described, and the destination path must be in one of the unit search paths, see UNIT FILE LOAD PATH section below for more details. Note that the target file may not exist, i.e. the symlink may be dangling. Unit files may specify aliases through the Alias= directive in the [Install] section. 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, the symlink /etc/systemd/system/ctrl-alt-del.service pointing to the reboot.target file will be created, and when Ctrl+Alt+Del is invoked, systemd will look for the ctrl-alt-del.service and execute reboot.service. systemd does not look at the [Install] section at all during normal operation, so any directives in that section only have an effect through the symlinks created during enablement. 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. Similar functionality exists for Requires= type dependencies as well, the directory suffix is .requires/ in this case. This functionality 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= and Requires=, see below. The preferred way to create symlinks in the .wants/ or .requires/ directories is by specifying the dependency in [Install] section of the target unit, and creating the symlink in the file system with the enable or preset commands of systemctl(1). The target can be a normal unit (either plain or a specific instance of a template unit). In case when the source unit is a template, the target can also be a template, in which case the instance will be "propagated" to the target unit to form a valid unit instance. The target of symlinks in .wants/ or .requires/ must thus point to a valid unit file location, i.e. the symlink target name must satisfy the described requirements, and the destination path must be in one of the unit search paths, see UNIT FILE LOAD PATH section below for more details. Note that the target file may not exist, i.e. the symlink may be dangling. 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 merged in the alphanumeric order and parsed after the main unit file itself has been parsed. This is useful to alter or add configuration settings for a unit, without having to modify unit files. Each drop-in file must contain appropriate section headers. For instantiated units, this logic will first look for the instance ".d/" subdirectory (e.g. "[email protected]/") and read its ".conf" files, followed by the template ".d/" subdirectory (e.g. "[email protected]/") and the ".conf" files there. Moreover for unit names containing dashes ("-"), the set of directories generated by repeatedly truncating the unit name after all dashes is searched too. Specifically, for a unit name foo-bar-baz.service not only the regular drop-in directory foo-bar-baz.service.d/ is searched but also both foo-bar-.service.d/ and foo-.service.d/. This is useful for defining common drop-ins for a set of related units, whose names begin with a common prefix. This scheme is particularly useful for mount, automount and slice units, whose systematic naming structure is built around dashes as component separators. Note that equally named drop-in files further down the prefix hierarchy override those further up, i.e. foo-bar-.service.d/10-override.conf overrides foo-.service.d/10-override.conf. In cases of unit aliases (described above), dropins for the aliased name and all aliases are loaded. In the example of default.target aliasing graphical.target, default.target.d/, default.target.wants/, default.target.requires/, graphical.target.d/, graphical.target.wants/, graphical.target.requires/ would all be read. For templates, dropins for the template, any template aliases, the template instance, and all alias instances are read. When just a specific template instance is aliased, then the dropins for the target template, the target template instance, and the alias template instance are read. In addition to /etc/systemd/system, the drop-in ".d/" directories for system services can be placed in /lib/systemd/system or /run/systemd/system directories. Drop-in files in /etc/ take precedence over those in /run/ which in turn take precedence over those in /lib/. Drop-in files under any of these directories take precedence over unit files wherever located. Multiple drop-in files with different names are applied in lexicographic order, regardless of which of the directories they reside in. Units also support a top-level drop-in with type.d/, where type may be e.g. "service" or "socket", that allows altering or adding to the settings of all corresponding unit files on the system. The formatting and precedence of applying drop-in configurations follow what is defined above. Files in type.d/ have lower precedence compared to files in name-specific override directories. The usual rules apply: multiple drop-in files with different names are applied in lexicographic order, regardless of which of the directories they reside in, so a file in type.d/ applies to a unit only if there are no drop-ins or masks with that name in directories with higher precedence. See Examples. 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. As mentioned above, a unit may be instantiated from a template file. 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 [email protected] is requested and no file by that name is found, systemd will look for [email protected] 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 Portability and Stability Promise[1].STRING ESCAPING FOR INCLUSION IN UNIT NAMES
Sometimes it is useful to convert arbitrary strings into unit names. To facilitate this, a method of string escaping is used, in order to map strings containing arbitrary byte values (except NUL) into valid unit names and their restricted character set. A common special case are unit names that reflect paths to objects in the file system hierarchy. Example: a device unit dev-sda.device refers to a device with the device node /dev/sda in the file system. The escaping algorithm operates as follows: given a string, any "/" character is replaced by "-", and all other characters which are not ASCII alphanumerics, ":", "_" or "." are replaced by C-style "\x2d" escapes. In addition, "." is replaced with such a C-style escape when it would appear as the first character in the escaped string. When the input qualifies as absolute file system path, this algorithm is extended slightly: the path to the root directory "/" is encoded as single dash "-". In addition, any leading, trailing or duplicate "/" characters are removed from the string before transformation. Example: /foo//bar/baz/ becomes "foo-bar-baz". This escaping is fully reversible, as long as it is known whether the escaped string was a path (the unescaping results are different for paths and non-path strings). The systemd-escape(1) command may be used to apply and reverse escaping on arbitrary strings. Use systemd-escape --path to escape path strings, and systemd-escape without --path otherwise.AUTOMATIC DEPENDENCIES
Implicit Dependencies
A number of unit dependencies are implicitly established, depending on unit type and unit configuration. These implicit dependencies can make unit configuration file cleaner. For the implicit dependencies in each unit type, please refer to section "Implicit Dependencies" in respective man pages. For example, service units with Type=dbus automatically acquire dependencies of type Requires= and After= on dbus.socket. See systemd.service(5) for details.Default Dependencies
Default dependencies are similar to implicit dependencies, but can be turned on and off by setting DefaultDependencies= to yes (the default) and no, while implicit dependencies are always in effect. See section "Default Dependencies" in respective man pages for the effect of enabling DefaultDependencies= in each unit types. For example, target units will complement all configured dependencies of type Wants= or Requires= with dependencies of type After=. See systemd.target(5) for details. Note that this behavior can be opted out by setting DefaultDependencies=no in the specified units, or it can be selectively overridden via an explicit Before= dependency.UNIT FILE LOAD PATH
Unit files are loaded from a set of paths determined during compilation, described in the two tables below. Unit files found in directories listed earlier override files with the same name in directories lower in the list. When the variable $SYSTEMD_UNIT_PATH is set, the contents of this variable overrides the unit load path. If $SYSTEMD_UNIT_PATH ends with an empty component (":"), the usual unit load path will be appended to the contents of the variable.Path | Description |
/etc/systemd/system.control | Persistent and transient configuration created using the dbus API |
/run/systemd/system.control | |
/run/systemd/transient | Dynamic configuration for transient units |
/run/systemd/generator.early | Generated units with high priority (see early-dir in systemd.generator(7)) |
/etc/systemd/system | System units created by the administrator |
/run/systemd/system | Runtime units |
/run/systemd/generator | Generated units with medium priority (see normal-dir in systemd.generator(7)) |
/usr/local/lib/systemd/system | System units installed by the administrator |
/lib/systemd/system | System units installed by the distribution package manager |
/run/systemd/generator.late | Generated units with low priority (see late-dir in systemd.generator(7)) |
Path | Description |
$XDG_CONFIG_HOME/systemd/user.control or ~/.config/systemd/user.control | Persistent and transient configuration created using the dbus API ($XDG_CONFIG_HOME is used if set, ~/.config otherwise) |
$XDG_RUNTIME_DIR/systemd/user.control | |
$XDG_RUNTIME_DIR/systemd/transient | Dynamic configuration for transient units |
$XDG_RUNTIME_DIR/systemd/generator.early | Generated units with high priority (see early-dir in systemd.generator(7)) |
$XDG_CONFIG_HOME/systemd/user or $HOME/.config/systemd/user | User configuration ($XDG_CONFIG_HOME is used if set, ~/.config otherwise) |
$XDG_CONFIG_DIRS/systemd/user or /etc/xdg/systemd/user | Additional configuration directories as specified by the XDG base directory specification ( $XDG_CONFIG_DIRS is used if set, /etc/xdg otherwise) |
/etc/systemd/user | User units created by the administrator |
$XDG_RUNTIME_DIR/systemd/user | Runtime units (only used when $XDG_RUNTIME_DIR is set) |
/run/systemd/user | Runtime units |
$XDG_RUNTIME_DIR/systemd/generator | Generated units with medium priority (see normal-dir in systemd.generator(7)) |
$XDG_DATA_HOME/systemd/user or $HOME/.local/share/systemd/user | Units of packages that have been installed in the home directory ($XDG_DATA_HOME is used if set, ~/.local/share otherwise) |
$XDG_DATA_DIRS/systemd/user or /usr/local/share/systemd/user and /usr/share/systemd/user | Additional data directories as specified by the XDG base directory specification ( $XDG_DATA_DIRS is used if set, /usr/local/share and /usr/share otherwise) |
$dir/systemd/user for each $dir in $XDG_DATA_DIRS | Additional locations for installed user units, one for each entry in $XDG_DATA_DIRS |
/usr/local/lib/systemd/user | User units installed by the administrator |
/usr/lib/systemd/user | User units installed by the distribution package manager |
$XDG_RUNTIME_DIR/systemd/generator.late | Generated units with low priority (see late-dir in systemd.generator(7)) |
systemd-analyze --user unit-paths
UNIT GARBAGE COLLECTION
The system and service manager loads a unit's configuration automatically when a unit is referenced for the first time. It will automatically unload the unit configuration and state again when the unit is not needed anymore ("garbage collection"). A unit may be referenced through a number of different mechanisms: 1.Another loaded unit references it with a
dependency such as After=, Wants=, ...
2.The unit is currently starting, running,
reloading or stopping.
3.The unit is currently in the failed
state. (But see below.)
4.A job for the unit is pending.
5.The unit is pinned by an active IPC client
program.
6.The unit is a special "perpetual"
unit that is always active and loaded. Examples for perpetual units are the
root mount unit -.mount or the scope unit init.scope that the service manager
itself lives in.
7.The unit has running processes associated
with it.
The garbage collection logic may be altered with the CollectMode= option,
which allows configuration whether automatic unloading of units that are in
failed state is permissible, see below.
Note that when a unit's configuration and state is unloaded, all execution
results, such as exit codes, exit signals, resource consumption and other
statistics are lost, except for what is stored in the log subsystem.
Use systemctl daemon-reload or an equivalent command to reload unit
configuration while the unit is already loaded. In this case all configuration
settings are flushed out and replaced with the new configuration (which
however might not be in effect immediately), however all runtime state is
saved/restored.
[UNIT] SECTION OPTIONS
The unit file may include a [Unit] section, which carries generic information about the unit that is not dependent on the type of unit: Description=A short human readable title of the unit. This
may be used by systemd (and other UIs) as a user-visible label for the
unit, so this string should identify the unit rather than describe it, despite
the name. This string also shouldn't just repeat the unit name. "Apache2
Web Server" is a good example. Bad examples are "high-performance
light-weight HTTP server" (too generic) or "Apache2"
(meaningless for people who do not know Apache, duplicates the unit name).
systemd may use this string as a noun in status messages
("Starting description...", "Started
description.", "Reached target description.",
"Failed to start description."), so it should be capitalized,
and should not be a full sentence, or a phrase with a continuous verb. Bad
examples include "exiting the container" or "updating the
database once per day.".
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.
Wants=
Configures (weak) requirement dependencies on
other units. This option may be specified more than once or multiple
space-separated units may be specified in one option in which case
dependencies for all listed names will be created. Dependencies of this type
may also be configured outside of the unit configuration file by adding a
symlink to a .wants/ directory accompanying the unit file. For details, see
above.
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, and this unit
will still be started. This is the recommended way to hook the start-up of one
unit to the start-up of another unit.
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 unit foo.service pulls in unit
bar.service as configured with Wants= 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.
Requires=
Similar to Wants=, but declares a
stronger requirement dependency. Dependencies of this type may also be
configured by adding a symlink to a .requires/ directory accompanying the unit
file.
If this unit gets activated, the units listed will be activated as well. If one
of the other units fails to activate, and an ordering dependency After=
on the failing unit is set, this unit will not be started. Besides, with or
without specifying After=, this unit will be stopped (or restarted) if
one of the other units is explicitly stopped (or restarted).
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=,
ConditionPathIsSymbolicLink=, ... — 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).
Requisite=
Similar to Requires=. However, if the
units listed here are not started already, they will not be started and the
starting of this unit will fail immediately. Requisite= does not imply
an ordering dependency, even if both units are started in the same
transaction. Hence this setting should usually be combined with After=,
to ensure this unit is not started before the other unit.
When Requisite=b.service is used on a.service, this dependency will show
as RequisiteOf=a.service in property listing of b.service.
RequisiteOf= dependency cannot be specified directly.
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 an unmet
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=.
When BindsTo=b.service is used on a.service, this dependency will show as
BoundBy=a.service in property listing of b.service. BoundBy=
dependency cannot be specified directly.
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.
When PartOf=b.service is used on a.service, this dependency will show as
ConsistsOf=a.service in property listing of b.service.
ConsistsOf= dependency cannot be specified directly.
Upholds=
Configures dependencies similar to
Wants=, but as long as this unit is up, all units listed in
Upholds= are started whenever found to be inactive or failed, and no
job is queued for them. While a Wants= dependency on another unit has a
one-time effect when this units started, a Upholds= dependency on it
has a continuous effect, constantly restarting the unit if necessary. This is
an alternative to the Restart= setting of service units, to ensure they
are kept running whatever happens.
When Upholds=b.service is used on a.service, this dependency will show as
UpheldBy=a.service in the property listing of b.service. The
UpheldBy= dependency cannot be specified directly.
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 does not imply an ordering dependency, similarly to the
Wants= and Requires= dependencies described above. This means
that to ensure that the conflicting unit is stopped before the other unit is
started, an After= or Before= dependency must be declared. It
doesn't matter which of the two ordering dependencies is used, because stop
jobs are always ordered before start jobs, see the discussion in
Before=/ After= below.
If unit A that conflicts with unit B is scheduled to be started at the same time
as B, the transaction will either fail (in case both are required parts 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
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 may be specified more than once, in which case
dependencies for all listed names are created.
Those two settings configure ordering dependencies between units. If unit
foo.service contains the setting Before=bar.service and both units are
being started, bar.service's start-up is delayed until foo.service has
finished starting up. After= is the inverse of Before=, i.e.
while Before= ensures that the configured unit is started before the
listed unit begins starting up, After= ensures the opposite, that the
listed unit is fully started up before the configured unit is started.
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. Note that
this does includes ExecStartPost= (or ExecStopPost= for the
shutdown case).
Note that those settings are independent of and orthogonal to the requirement
dependencies as configured by Requires=, Wants=,
Requisite=, or BindsTo=. It is a common pattern to include a
unit name in both the After= and Wants= options, in which case
the unit listed will be started before the unit that is configured with these
options.
Note that Before= dependencies on device units have no effect and are not
supported. Devices generally become available as a result of an external
hotplug event, and systemd creates the corresponding device unit without
delay.
OnFailure=
A space-separated list of one or more units
that are activated when this unit enters the "failed" state.
OnSuccess=
A space-separated list of one or more units
that are activated when this unit enters the "inactive" state.
PropagatesReloadTo=, ReloadPropagatedFrom=
A space-separated list of one or more units to
which reload requests from this unit shall be propagated to, or units from
which reload requests shall be propagated to this unit, respectively. Issuing
a reload request on a unit will automatically also enqueue reload requests on
all units that are linked to it using these two settings.
PropagatesStopTo=, StopPropagatedFrom=
A space-separated list of one or more units to
which stop requests from this unit shall be propagated to, or units from which
stop requests shall be propagated to this unit, respectively. Issuing a stop
request on a unit will automatically also enqueue stop requests on all units
that are linked to it using 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=, NetworkNamespacePath=, PrivateIPC=,
IPCNamespacePath=, 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/, IPC namespace 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=/NetworkNamespacePath=,
PrivateIPC=/IPCNamespacePath= 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.
OnSuccessJobMode=, 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 OnSuccess=/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 OnSuccess=/OnFailure=.
IgnoreOnIsolate=
Takes a boolean argument. If true, this
unit will not be stopped when isolating another unit. Defaults to false
for service, target, socket, timer, and path units, and true for slice,
scope, device, swap, mount, and automount units.
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 yes, (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
no. It is highly recommended to leave this option enabled for the
majority of common units. If set to no, this option does not disable
all implicit dependencies, just non-essential ones.
CollectMode=
Tweaks the "garbage collection"
algorithm for this unit. Takes one of inactive or
inactive-or-failed. If set to inactive the unit will be unloaded
if it is in the inactive state and is not referenced by clients, jobs
or other units — however it is not unloaded if it is in the
failed state. In failed mode, failed units are not unloaded
until the user invoked systemctl reset-failed on them to reset the
failed state, or an equivalent command. This behaviour is altered if
this option is set to inactive-or-failed: in this case the unit is
unloaded even if the unit is in a failed state, and thus an explicitly
resetting of the failed state is not necessary. Note that if this mode
is used unit results (such as exit codes, exit signals, consumed resources,
...) are flushed out immediately after the unit completed, except for what is
stored in the logging subsystem. Defaults to inactive.
FailureAction=, SuccessAction=
Configure the action to take when the unit
stops and enters a failed state or inactive state. Takes one of none,
reboot, reboot-force, reboot-immediate, poweroff,
poweroff-force, poweroff-immediate, exit, and
exit-force. In system mode, all options are allowed. In user mode, only
none, exit, and exit-force are allowed. Both options
default to none.
If none is set, no action will be triggered. 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 (i.e. equivalent to systemctl
reboot -ff). Similarly, poweroff, poweroff-force,
poweroff-immediate have the effect of powering down the system with
similar semantics. exit causes the manager to exit following the normal
shutdown procedure, and exit-force causes it terminate without shutting
down services. When exit or exit-force is used by default the
exit status of the main process of the unit (if this applies) is returned from
the service manager. However, this may be overridden with
FailureActionExitStatus=/ SuccessActionExitStatus=, see
below.
FailureActionExitStatus=, SuccessActionExitStatus=
Controls the exit status to propagate back to
an invoking container manager (in case of a system service) or service manager
(in case of a user manager) when the
FailureAction=/SuccessAction= are set to exit or
exit-force and the action is triggered. By default the exit status of
the main process of the triggering unit (if this applies) is propagated. Takes
a value in the range 0...255 or the empty string to request default
behaviour.
JobTimeoutSec=, JobRunningTimeoutSec=
JobTimeoutSec= specifies a timeout for
the whole job that starts running when the job is queued.
JobRunningTimeoutSec= specifies a timeout that starts running when the
queued job is actually started. If either limit is reached, the job will be
cancelled, the unit however will not change state or even enter the
"failed" mode.
Both settings take a time span with the default unit of seconds, but other units
may be specified, see systemd.time(5). The default is
"infinity" (job timeouts disabled), except for device units where
JobRunningTimeoutSec= defaults to DefaultDeviceTimeoutSec=.
Note: these timeouts are independent from any unit-specific timeouts (for
example, the timeout set with TimeoutStartSec= in service units). The
job timeout has no effect on the unit itself. 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=, JobTimeoutRebootArgument=
JobTimeoutAction= optionally configures
an additional action to take when the timeout is hit, see description of
JobTimeoutSec= and JobRunningTimeoutSec= above. It takes the
same values as StartLimitAction=. Defaults to none.
JobTimeoutRebootArgument= configures an optional reboot string to pass to
the reboot(2) system call.
StartLimitIntervalSec=interval,
StartLimitBurst= burst
Configure unit start rate limiting. Units
which are started more than burst times within an interval time
span are not permitted to start any more. Use StartLimitIntervalSec= to
configure the checking interval and StartLimitBurst= to configure how
many starts per interval are allowed.
interval is a time span with the default unit of seconds, but other units
may be specified, see systemd.time(5). Defaults to
DefaultStartLimitIntervalSec= in manager configuration file, and may be
set to 0 to disable any kind of rate limiting. burst is a number and
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 or from a timer or socket at a later point, after the
interval has passed. From that point on, the restart logic is activated
again. 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. Rate-limiting is
enforced after any unit condition checks are executed, and hence unit
activations with failing conditions do not count towards the rate limit.
When a unit is unloaded due to the garbage collection logic (see above) its rate
limit counters are flushed out too. This means that configuring start rate
limiting for a unit that is not referenced continuously has no effect.
This setting does not apply to slice, target, device, and scope units, since
they are unit types whose activation may either never fail, or may succeed
only a single time.
StartLimitAction=
Configure an additional action to take if the
rate limit configured with StartLimitIntervalSec= and
StartLimitBurst= is hit. Takes the same values as the
FailureAction=/ SuccessAction= settings. If none is set,
hitting the rate limit will trigger no action except that the start will not
be permitted. Defaults to none.
RebootArgument=
Configure the optional argument for the
reboot(2) system call if StartLimitAction= or
FailureAction= is a reboot action. This works just like the optional
argument to systemctl reboot command.
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.
Conditions and Asserts
Unit files may also include a number of Condition...= and Assert...= settings. Before the unit is started, systemd will verify that the specified conditions and asserts are true. If not, the starting of the unit will be (mostly silently) skipped (in case of conditions), or aborted with an error message (in case of asserts). Failing conditions or asserts will not result in the unit being moved into the "failed" state. The conditions and asserts are checked at the time the queued start job is to be executed. The ordering dependencies are still respected, so other units are still pulled in and ordered as if this unit was successfully activated, and the conditions and asserts are executed the precise moment the unit would normally start and thus can validate system state after the units ordered before completed initialization. Use condition expressions for skipping units that do not apply to the local system, for example because the kernel or runtime environment doesn't require their functionality. 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 use a pipe symbol ("|") after the equals sign ("Condition...=|..."), which causes the condition to become a triggering condition. If at least one triggering condition is defined for a unit, then the unit will be started if at least one of the triggering conditions of the unit applies and all of the regular (i.e. non-triggering) conditions apply. If you prefix an argument with the pipe symbol and an exclamation mark, the pipe symbol must be passed first, the exclamation second. 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. The AssertArchitecture=, AssertVirtualization=, ... options are similar to conditions but cause the start job to fail (instead of being skipped). The failed check is logged. Units with unmet conditions are considered to be in a clean state and will be garbage collected if they are not referenced. This means that when queried, the condition failure may or may not show up in the state of the unit. Note that neither assertion nor condition expressions result in unit state changes. Also note that both are checked at the time the job is to be executed, i.e. long after depending jobs and it itself were queued. Thus, neither condition nor assertion expressions are suitable for conditionalizing unit dependencies. The condition verb of systemd-analyze(1) can be used to test condition and assert expressions. Except for ConditionPathIsSymbolicLink=, all path checks follow symlinks. ConditionArchitecture=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", or
"native".
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.
ConditionFirmware=
Check whether the system's firmware is of a
certain type. The following values are possible:
ConditionVirtualization=
•"uefi" matches systems with
EFI.
•"device-tree" matches
systems with a device tree.
•"device-tree-compatible(value)"
matches systems with a device tree that is compatible with
"value".
•"smbios-field(field
operator value)" matches systems with a SMBIOS field
containing a certain value. field is the name of the SMBIOS field
exposed as "sysfs" attribute file below /sys/class/dmi/id/.
operator is one of "<", "<=",
">=", ">", "==", "<>" for
version comparisons, "=" and "!=" for literal string
comparisons, or "$=", "!$=" for shell-style glob
comparisons. value is the expected value of the SMBIOS field value
(possibly containing shell style globs in case "$="/"!$="
is used).
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", "amazon", "zvm",
"vmware", "microsoft", "oracle",
"powervm", "xen", "bochs", "uml",
"bhyve", "qnx", "apple", "sre",
"openvz", "lxc", "lxc-libvirt",
"systemd-nspawn", "docker", "podman",
"rkt", "wsl", "proot", "pouch",
"acrn" 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=
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=
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 by "="). 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. This operates
on the kernel command line communicated to userspace via /proc/cmdline, except
when the service manager is invoked as payload of a container manager, in
which case the command line of PID 1 is used instead (i.e.
/proc/1/cmdline).
ConditionKernelVersion=
ConditionKernelVersion= may be used to
check whether the kernel version (as reported by uname -r) matches a
certain expression, or if prefixed with the exclamation mark, does not match.
The argument must be a list of (potentially quoted) expressions. Each
expression starts with one of "=" or "!=" for string
comparisons, "<", "<=", "==",
"<>", ">=", ">" for version
comparisons, or "$=", "!$=" for a shell-style glob match.
If no operator is specified, "$=" is implied.
Note that using the kernel version string is an unreliable way to determine
which features are supported by a kernel, because of the widespread practice
of backporting drivers, features, and fixes from newer upstream kernels into
older versions provided by distributions. Hence, this check is inherently
unportable and should not be used for units which may be used on different
distributions.
ConditionCredential=
ConditionCredential= may be used to
check whether a credential by the specified name was passed into the service
manager. See System and Service Credentials[2] for details about
credentials. If used in services for the system service manager this may be
used to conditionalize services based on system credentials passed in. If used
in services for the per-user service manager this may be used to
conditionalize services based on credentials passed into the [email protected]
service instance belonging to the user. The argument must be a valid
credential name.
ConditionEnvironment=
ConditionEnvironment= may be used to
check whether a specific environment variable is set (or if prefixed with the
exclamation mark — unset) in the service manager's environment block.
The argument may be a single word, to check if the variable with this name is
defined in the environment block, or an assignment ("
name=value"), to check if the variable with this exact
value is defined. Note that the environment block of the service manager
itself is checked, i.e. not any variables defined with Environment= or
EnvironmentFile=, as described above. This is particularly useful when
the service manager runs inside a containerized environment or as per-user
service manager, in order to check for variables passed in by the enclosing
container manager or PAM.
ConditionSecurity=
ConditionSecurity= may be used to check
whether the given security technology is enabled on the system. Currently, the
recognized values are "selinux", "apparmor",
"tomoyo", "ima", "smack", "audit",
"uefi-secureboot" and "tpm2". The test may be negated by
prepending an exclamation mark.
ConditionCapability=
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=
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 "!" (to invert 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.
If the systemd.condition-needs-update= option is specified on the kernel
command line (taking a boolean), it will override the result of this condition
check, taking precedence over any file modification time checks. If the kernel
command line option is used, systemd-update-done.service will not have
immediate effect on any following ConditionNeedsUpdate= checks, until
the system is rebooted where the kernel command line option is not specified
anymore.
Note that to make this scheme effective, the timestamp of /usr/ should be
explicitly updated after its contents are modified. The kernel will
automatically update modification timestamp on a directory only when immediate
children of a directory are modified; an modification of nested files will not
automatically result in mtime of /usr/ being updated.
Also note that if the update method includes a call to execute appropriate
post-update steps itself, it should not touch the timestamp of /usr/. In a
typical distribution packaging scheme, packages will do any required update
steps as part of the installation or upgrade, to make package contents
immediately usable. ConditionNeedsUpdate= should be used with other
update mechanisms where such an immediate update does not happen.
ConditionFirstBoot=
Takes a boolean argument. This condition may
be used to conditionalize units on whether the system is booting up for the
first time. This roughly means that /etc/ was unpopulated when the system
started booting (for details, see "First Boot Semantics" in
machine-id(5)). First boot is considered finished (this condition will
evaluate as false) after the manager has finished the startup phase.
This condition 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.
For robustness, units with ConditionFirstBoot=yes should order themselves
before first-boot-complete.target and pull in this passive target with
Wants=. This ensures that in a case of an aborted first boot, these
units will be re-run during the next system startup.
If the systemd.condition-first-boot= option is specified on the kernel
command line (taking a boolean), it will override the result of this condition
check, taking precedence over /etc/machine-id existence checks.
ConditionPathExists=
Check for the existence of a file. 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=
ConditionPathExistsGlob= is similar to
ConditionPathExists=, but checks for the existence of at least one file
or directory matching the specified globbing pattern.
ConditionPathIsDirectory=
ConditionPathIsDirectory= is similar to
ConditionPathExists= but verifies that a certain path exists and is a
directory.
ConditionPathIsSymbolicLink=
ConditionPathIsSymbolicLink= is similar
to ConditionPathExists= but verifies that a certain path exists and is
a symbolic link.
ConditionPathIsMountPoint=
ConditionPathIsMountPoint= is similar
to ConditionPathExists= but verifies that a certain path exists and is
a mount point.
ConditionPathIsReadWrite=
ConditionPathIsReadWrite= is similar to
ConditionPathExists= but verifies that the underlying file system is
readable and writable (i.e. not mounted read-only).
ConditionPathIsEncrypted=
ConditionPathIsEncrypted= is similar to
ConditionPathExists= but verifies that the underlying file system's
backing block device is encrypted using dm-crypt/LUKS. Note that this check
does not cover ext4 per-directory encryption, and only detects block level
encryption. Moreover, if the specified path resides on a file system on top of
a loopback block device, only encryption above the loopback device is
detected. It is not detected whether the file system backing the loopback
block device is encrypted.
ConditionDirectoryNotEmpty=
ConditionDirectoryNotEmpty= is similar
to ConditionPathExists= but verifies that a certain path exists and is
a non-empty directory.
ConditionFileNotEmpty=
ConditionFileNotEmpty= is similar to
ConditionPathExists= but verifies that a certain path exists and refers
to a regular file with a non-zero size.
ConditionFileIsExecutable=
ConditionFileIsExecutable= is similar
to ConditionPathExists= but verifies that a certain path exists, is a
regular file, and marked executable.
ConditionUser=
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=
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 support the special value
"@system".
ConditionControlGroupController=
Check whether given cgroup controllers (e.g.
"cpu") are available for use on the system or whether the legacy v1
cgroup or the modern v2 cgroup hierarchy is used.
Multiple controllers may be passed with a space separating them; in this case
the condition will only pass if all listed controllers are available for use.
Controllers unknown to systemd are ignored. Valid controllers are
"cpu", "io", "memory", and "pids".
Even if available in the kernel, a particular controller may not be available
if it was disabled on the kernel command line with
cgroup_disable=controller.
Alternatively, two special strings "v1" and "v2" may be
specified (without any controller names). "v2" will pass if the
unified v2 cgroup hierarchy is used, and "v1" will pass if the
legacy v1 hierarchy or the hybrid hierarchy are used. Note that legacy or
hybrid hierarchies have been deprecated. See systemd(1) for more
information.
ConditionMemory=
Verify that the specified amount of system
memory is available to the current system. Takes a memory size in bytes as
argument, optionally prefixed with a comparison operator "<",
"<=", "=" (or "=="), "!=" (or
"<>"), ">=", ">". On bare-metal
systems compares the amount of physical memory in the system with the
specified size, adhering to the specified comparison operator. In containers
compares the amount of memory assigned to the container instead.
ConditionCPUs=
Verify that the specified number of CPUs is
available to the current system. Takes a number of CPUs as argument,
optionally prefixed with a comparison operator "<",
"<=", "=" (or "=="), "!=" (or
"<>"), ">=", ">". Compares the
number of CPUs in the CPU affinity mask configured of the service manager
itself with the specified number, adhering to the specified comparison
operator. On physical systems the number of CPUs in the affinity mask of the
service manager usually matches the number of physical CPUs, but in special
and virtual environments might differ. In particular, in containers the
affinity mask usually matches the number of CPUs assigned to the container and
not the physically available ones.
ConditionCPUFeature=
Verify that a given CPU feature is available
via the "CPUID" instruction. This condition only does something on
i386 and x86-64 processors. On other processors it is assumed that the CPU
does not support the given feature. It checks the leaves "1",
"7", "0x80000001", and "0x80000007". Valid
values are: "fpu", "vme", "de", "pse",
"tsc", "msr", "pae", "mce",
"cx8", "apic", "sep", "mtrr",
"pge", "mca", "cmov", "pat",
"pse36", "clflush", "mmx", "fxsr",
"sse", "sse2", "ht", "pni",
"pclmul", "monitor", "ssse3", "fma3",
"cx16", "sse4_1", "sse4_2", "movbe",
"popcnt", "aes", "xsave", "osxsave",
"avx", "f16c", "rdrand", "bmi1",
"avx2", "bmi2", "rdseed", "adx",
"sha_ni", "syscall", "rdtscp", "lm",
"lahf_lm", "abm", "constant_tsc".
ConditionOSRelease=
Verify that a specific "key=value"
pair is set in the host's os-release(5).
Other than exact string matching (with "=" and "!="),
relative comparisons are supported for versioned parameters (e.g.
"VERSION_ID"; with "<", "<=",
"==", "<>", ">=", ">"),
and shell-style wildcard comparisons ("*", "?",
"[]") are supported with the "$=" (match) and
"!$=" (non-match).
ConditionMemoryPressure=, ConditionCPUPressure=,
ConditionIOPressure=
Verify that the overall system (memory, CPU or
IO) pressure is below or equal to a threshold. This setting takes a threshold
value as argument. It can be specified as a simple percentage value, suffixed
with "%", in which case the pressure will be measured as an average
over the last five minutes before the attempt to start the unit is performed.
Alternatively, the average timespan can also be specified using "/"
as a separator, for example: "10%/1min". The supported timespans
match what the kernel provides, and are limited to "10sec",
"1min" and "5min". The "full" PSI will be
checked first, and if not found "some" will be checked. For more
details, see the documentation on PSI (Pressure Stall Information)[3].
Optionally, the threshold value can be prefixed with the slice unit under which
the pressure will be checked, followed by a ":". If the slice unit
is not specified, the overall system pressure will be measured, instead of a
particular cgroup's.
AssertArchitecture=, AssertVirtualization=, AssertHost=,
AssertKernelCommandLine=, AssertKernelVersion=,
AssertCredential=, AssertEnvironment=, AssertSecurity=,
AssertCapability=, AssertACPower=, AssertNeedsUpdate=,
AssertFirstBoot=, AssertPathExists=,
AssertPathExistsGlob=, AssertPathIsDirectory=,
AssertPathIsSymbolicLink=, AssertPathIsMountPoint=,
AssertPathIsReadWrite=, AssertPathIsEncrypted=,
AssertDirectoryNotEmpty=, AssertFileNotEmpty=,
AssertFileIsExecutable=, AssertUser=, AssertGroup=,
AssertControlGroupController=, AssertMemory=,
AssertCPUs=, AssertCPUFeature=, AssertOSRelease=,
AssertMemoryPressure=, AssertCPUPressure=,
AssertIOPressure=
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). Note that
hitting a configured assertion does not cause the unit to enter the
"failed" state (or in fact result in any state change of the unit),
it affects only the job queued for it. 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.
MAPPING OF UNIT PROPERTIES TO THEIR INVERSES
Unit settings that create a relationship with a second unit usually show up in properties of both units, for example in systemctl show output. In some cases the name of the property is the same as the name of the configuration setting, but not always. This table lists the properties that are shown on two units which are connected through some dependency, and shows which property on "source" unit corresponds to which property on the "target" unit."Forward" property | "Reverse" property | Where used | |
Before= | After= | [Unit] section | |
After= | Before= | ||
Requires= | RequiredBy= | [Unit] section | [Install] section |
Wants= | WantedBy= | [Unit] section | [Install] section |
PartOf= | ConsistsOf= | [Unit] section | an automatic property |
BindsTo= | BoundBy= | [Unit] section | an automatic property |
Requisite= | RequisiteOf= | [Unit] section | an automatic property |
Conflicts= | ConflictedBy= | [Unit] section | an automatic property |
Triggers= | TriggeredBy= | Automatic properties, see notes below | |
PropagatesReloadTo= | ReloadPropagatedFrom= | [Unit] section | |
ReloadPropagatedFrom= | PropagatesReloadTo= | ||
PropagatesStopTo= | StopPropagatedFrom= | [Unit] section | |
StopPropagatedFrom= | PropagatesStopTo= | ||
Following= | n/a | An automatic property |
[INSTALL] SECTION OPTIONS
Unit files may include an [Install] section, which carries installation information for the unit. This section is not interpreted by systemd(1) during runtime; it is used by the enable and disable commands of the systemctl(1) tool during installation of a unit. 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 filename. 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 of a dependency
of type Wants= or Requires= being 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.
In case of template units listing non template units, the listing unit must have
DefaultInstance= set, or systemctl enable must be called with an
instance name. The instance (default or specified) will be added to the
.wants/ or .requires/ list of the listed unit. For example,
WantedBy=getty.target in a service [email protected] will result in
systemctl enable [email protected] creating a
getty.target.wants/[email protected] link to [email protected]. This also
applies to listing specific instances of templated units: this specific
instance will gain the dependency. A template unit may also list a template
unit, in which case a generic dependency will be added where each instance of
the listing unit will have a dependency on an instance of the listed template
with the same instance value. For example, WantedBy=[email protected]
in a service [email protected] will result in systemctl enable
[email protected] creating a [email protected]/[email protected] link
to [email protected], which applies to all instances of
[email protected].
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: %a, %b, %B, %g,
%G, %H, %i, %j, %l, %m, %n, %N, %o, %p, %u, %U, %v, %w, %W, %%. For their
meaning see the next section.
SPECIFIERS
Many settings resolve specifiers which may be used to write generic unit files referring to runtime or unit parameters that are replaced when the unit files are loaded. Specifiers must be known and resolvable for the setting to be valid. The following specifiers are understood:Specifier | Meaning | Details |
"%a" | Architecture | A short string identifying the architecture of the local system. A string such as x86, x86-64 or arm64. See the architectures defined for ConditionArchitecture= above for a full list. |
"%A" | Operating system image version | The operating system image version identifier of the running system, as read from the IMAGE_VERSION= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%b" | Boot ID | The boot ID of the running system, formatted as string. See random(4) for more information. |
"%B" | Operating system build ID | The operating system build identifier of the running system, as read from the BUILD_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%C" | Cache directory root | This is either /var/cache (for the system manager) or the path "$XDG_CACHE_HOME" resolves to (for user managers). |
"%d" | Credentials directory | This is the value of the "$CREDENTIALS_DIRECTORY" environment variable if available. See section "Credentials" in systemd.exec(5) for more information. |
"%E" | Configuration directory root | This is either /etc/ (for the system manager) or the path "$XDG_CONFIG_HOME" resolves to (for user managers). |
"%f" | Unescaped filename | This is either the unescaped instance name (if applicable) with / prepended (if applicable), or the unescaped prefix name prepended with /. This implements unescaping according to the rules for escaping absolute file system paths discussed above. |
"%g" | User group | This is the name of the group running the service manager instance. In case of the system manager this resolves to "root". |
"%G" | User GID | This is the numeric GID of the user running the service manager instance. In case of the system manager this resolves to "0". |
"%h" | User home directory | This is the home directory of the user running the service manager instance. In case of the system manager this resolves to "/root". Note that this setting is not influenced by the User= setting configurable in the [Service] section of the service unit. |
"%H" | Host name | The hostname of the running system at the point in time the unit configuration is loaded. |
"%i" | Instance name | For instantiated units this is the string between the first "@" character and the type suffix. Empty for non-instantiated units. |
"%I" | Unescaped instance name | Same as "%i", but with escaping undone. |
"%j" | Final component of the prefix | This is the string between the last "-" and the end of the prefix name. If there is no "-", this is the same as "%p". |
"%J" | Unescaped final component of the prefix | Same as "%j", but with escaping undone. |
"%l" | Short host name | The hostname of the running system at the point in time the unit configuration is loaded, truncated at the first dot to remove any domain component. |
"%L" | Log directory root | This is either /var/log (for the system manager) or the path "$XDG_CONFIG_HOME" resolves to with /log appended (for user managers). |
"%m" | Machine ID | The machine ID of the running system, formatted as string. See machine-id(5) for more information. |
"%M" | Operating system image identifier | The operating system image identifier of the running system, as read from the IMAGE_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%n" | Full unit name | |
"%N" | Full unit name | Same as "%n", but with the type suffix removed. |
"%o" | Operating system ID | The operating system identifier of the running system, as read from the ID= field of /etc/os-release. See os-release(5) for more information. |
"%p" | Prefix name | For instantiated units, this refers to the string before the first "@" character of the unit name. For non-instantiated units, same as "%N". |
"%P" | Unescaped prefix name | Same as "%p", but with escaping undone. |
"%q" | Pretty host name | The pretty hostname of the running system at the point in time the unit configuration is loaded, as read from the PRETTY_HOSTNAME= field of /etc/machine-info. If not set, resolves to the short hostname. See machine-info(5) for more information. |
"%s" | User shell | This is the shell of the user running the service manager instance. |
"%S" | State directory root | This is either /var/lib (for the system manager) or the path "$XDG_CONFIG_HOME" resolves to (for user managers). |
"%t" | Runtime directory root | This is either /run/ (for the system manager) or the path "$XDG_RUNTIME_DIR" resolves to (for user managers). |
"%T" | Directory for temporary files | This is either /tmp or the path "$TMPDIR", "$TEMP" or "$TMP" are set to. (Note that the directory may be specified without a trailing slash.) |
"%u" | User name | This is the name of the user running the service manager instance. In case of the system manager this resolves to "root". Note that this setting is not influenced by the User= setting configurable in the [Service] section of the service unit. |
"%U" | User UID | This is the numeric UID of the user running the service manager instance. In case of the system manager this resolves to "0". Note that this setting is not influenced by the User= setting configurable in the [Service] section of the service unit. |
"%v" | Kernel release | Identical to uname -r output. |
"%V" | Directory for larger and persistent temporary files | This is either /var/tmp or the path "$TMPDIR", "$TEMP" or "$TMP" are set to. (Note that the directory may be specified without a trailing slash.) |
"%w" | Operating system version ID | The operating system version identifier of the running system, as read from the VERSION_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%W" | Operating system variant ID | The operating system variant identifier of the running system, as read from the VARIANT_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%y" | The path to the fragment | This is the path where the main part of the unit file is located. For linked unit files, the real path outside of the unit search directories is used. For units that don't have a fragment file, this specifier will raise an error. |
"%Y" | The directory of the fragment | This is the directory part of "%y". |
"%%" | Single percent sign | Use "%%" in place of "%" to specify a single percent sign. |
EXAMPLES
Example 1. Allowing units to be enabled[Unit] Description=Foo [Service] ExecStart=/usr/sbin/foo-daemon [Install] WantedBy=multi-user.target
[Unit] Description=Some HTTP server After=remote-fs.target sqldb.service Requires=sqldb.service AssertPathExists=/srv/webserver [Service] Type=notify ExecStart=/usr/sbin/some-fancy-httpd-server Nice=5 [Install] WantedBy=multi-user.target
[Unit] Description=Some HTTP server After=remote-fs.target sqldb.service memcached.service Requires=sqldb.service memcached.service AssertPathExists= /srv/www [Service] Type=notify ExecStart=/usr/sbin/some-fancy-httpd-server Nice=0 PrivateTmp=yes [Install] WantedBy=multi-user.target
[Unit] After=memcached.service Requires=memcached.service # Reset all assertions and then re-add the condition we want AssertPathExists= AssertPathExists=/srv/www [Service] Nice=0 PrivateTmp=yes
[Unit] Description=My failure handler for %i [Service] Type=oneshot # Perform some special action for when %i exits unexpectedly. ExecStart=/usr/sbin/myfailurehandler %i
[Unit] OnFailure=failure-handler@%N.service
mkdir /etc/systemd/system/[email protected]/ ln -s /dev/null /etc/systemd/system/[email protected]/10-all.conf systemctl daemon-reload
SEE ALSO
systemd(1), systemctl(1), systemd-system.conf(5), systemd.special(7), systemd.service(5), systemd.socket(5), systemd.device(5), systemd.mount(5), systemd.automount(5), systemd.swap(5), systemd.target(5), systemd.path(5), systemd.timer(5), systemd.scope(5), systemd.slice(5), systemd.time(7), systemd-analyze(1), capabilities(7), systemd.directives(7), uname(1)NOTES
- 1.
- Interface Portability and Stability Promise
- 2.
- System and Service Credentials
- 3.
- PSI (Pressure Stall Information)
systemd 252 |