systemd.service(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | SERVICE TEMPLATES | AUTOMATIC DEPENDENCIES | OPTIONS | COMMAND LINES | EXAMPLES | SEE ALSO | NOTES | COLOPHON

SYSTEMD.SERVICE(5)           systemd.service          SYSTEMD.SERVICE(5)

NAME         top

       systemd.service - Service unit configuration

SYNOPSIS         top

       service.service

DESCRIPTION         top

       A unit configuration file whose name ends in ".service" encodes
       information about a process controlled and supervised by systemd.

       This man page lists the configuration options specific to this
       unit type. See systemd.unit(5) for the common options of all unit
       configuration files. The common configuration items are
       configured in the generic [Unit] and [Install] sections. The
       service specific configuration options are configured in the
       [Service] section.

       Additional options are listed in systemd.exec(5), which define
       the execution environment the commands are executed in, and in
       systemd.kill(5), which define the way the processes of the
       service are terminated, and in systemd.resource-control(5), which
       configure resource control settings for the processes of the
       service.

       If a service is requested under a certain name but no unit
       configuration file is found, systemd looks for a SysV init script
       by the same name (with the .service suffix removed) and
       dynamically creates a service unit from that script. This is
       useful for compatibility with SysV. Note that this compatibility
       is quite comprehensive but not 100%. For details about the
       incompatibilities, see the Incompatibilities with SysV[1]
       document.

       The systemd-run(1) command allows creating .service and .scope
       units dynamically and transiently from the command line.

SERVICE TEMPLATES         top

       It is possible for systemd services to take a single argument via
       the "service@argument.service" syntax. Such services are called
       "instantiated" services, while the unit definition without the
       argument parameter is called a "template". An example could be a
       dhcpcd@.service service template which takes a network interface
       as a parameter to form an instantiated service. Within the
       service file, this parameter or "instance name" can be accessed
       with %-specifiers. See systemd.unit(5) for details.

AUTOMATIC DEPENDENCIES         top

   Implicit Dependencies
       The following dependencies are implicitly added:

       •   Services with Type=dbus set automatically acquire
           dependencies of type Requires= and After= on dbus.socket.

       •   Socket activated services are automatically ordered after
           their activating .socket units via an automatic After=
           dependency. Services also pull in all .socket units listed in
           Sockets= via automatic Wants= and After= dependencies.

       Additional implicit dependencies may be added as result of
       execution and resource control parameters as documented in
       systemd.exec(5) and systemd.resource-control(5).

   Default Dependencies
       The following dependencies are added unless
       DefaultDependencies=no is set:

       •   Service units will have dependencies of type Requires= and
           After= on sysinit.target, a dependency of type After= on
           basic.target as well as dependencies of type Conflicts= and
           Before= on shutdown.target. These ensure that normal service
           units pull in basic system initialization, and are terminated
           cleanly prior to system shutdown. Only services involved with
           early boot or late system shutdown should disable this
           option.

       •   Instanced service units (i.e. service units with an "@" in
           their name) are assigned by default a per-template slice unit
           (see systemd.slice(5)), named after the template unit,
           containing all instances of the specific template. This slice
           is normally stopped at shutdown, together with all template
           instances. If that is not desired, set DefaultDependencies=no
           in the template unit, and either define your own per-template
           slice unit file that also sets DefaultDependencies=no, or set
           Slice=system.slice (or another suitable slice) in the
           template unit. Also see systemd.resource-control(5).

OPTIONS         top

       Service files must include a [Service] section, which carries
       information about the service and the process it supervises. A
       number of options that may be used in this section are shared
       with other unit types. These options are documented in
       systemd.exec(5), systemd.kill(5) and systemd.resource-control(5).
       The options specific to the [Service] section of service units
       are the following:

       Type=
           Configures the process start-up type for this service unit.
           One of simple, exec, forking, oneshot, dbus, notify or idle:

           •   If set to simple (the default if ExecStart= is specified
               but neither Type= nor BusName= are), the service manager
               will consider the unit started immediately after the main
               service process has been forked off. It is expected that
               the process configured with ExecStart= is the main
               process of the service. In this mode, if the process
               offers functionality to other processes on the system,
               its communication channels should be installed before the
               service is started up (e.g. sockets set up by systemd,
               via socket activation), as the service manager will
               immediately proceed starting follow-up units, right after
               creating the main service process, and before executing
               the service's binary. Note that this means systemctl
               start command lines for simple services will report
               success even if the service's binary cannot be invoked
               successfully (for example because the selected User=
               doesn't exist, or the service binary is missing).

           •   The exec type is similar to simple, but the service
               manager will consider the unit started immediately after
               the main service binary has been executed. The service
               manager will delay starting of follow-up units until that
               point. (Or in other words: simple proceeds with further
               jobs right after fork() returns, while exec will not
               proceed before both fork() and execve() in the service
               process succeeded.) Note that this means systemctl start
               command lines for exec services will report failure when
               the service's binary cannot be invoked successfully (for
               example because the selected User= doesn't exist, or the
               service binary is missing).

           •   If set to forking, it is expected that the process
               configured with ExecStart= will call fork() as part of
               its start-up. The parent process is expected to exit when
               start-up is complete and all communication channels are
               set up. The child continues to run as the main service
               process, and the service manager will consider the unit
               started when the parent process exits. This is the
               behavior of traditional UNIX services. If this setting is
               used, it is recommended to also use the PIDFile= option,
               so that systemd can reliably identify the main process of
               the service. systemd will proceed with starting follow-up
               units as soon as the parent process exits.

           •   Behavior of oneshot is similar to simple; however, the
               service manager will consider the unit up after the main
               process exits. It will then start follow-up units.
               RemainAfterExit= is particularly useful for this type of
               service.  Type=oneshot is the implied default if neither
               Type= nor ExecStart= are specified. Note that if this
               option is used without RemainAfterExit= the service will
               never enter "active" unit state, but directly transition
               from "activating" to "deactivating" or "dead" since no
               process is configured that shall run continuously. In
               particular this means that after a service of this type
               ran (and which has RemainAfterExit= not set) it will not
               show up as started afterwards, but as dead.

           •   Behavior of dbus is similar to simple; however, it is
               expected that the service acquires a name on the D-Bus
               bus, as configured by BusName=. systemd will proceed with
               starting follow-up units after the D-Bus bus name has
               been acquired. Service units with this option configured
               implicitly gain dependencies on the dbus.socket unit.
               This type is the default if BusName= is specified. A
               service unit of this type is considered to be in the
               activating state until the specified bus name is
               acquired. It is considered activated while the bus name
               is taken. Once the bus name is released the service is
               considered being no longer functional which has the
               effect that the service manager attempts to terminate any
               remaining processes belonging to the service. Services
               that drop their bus name as part of their shutdown logic
               thus should be prepared to receive a SIGTERM (or
               whichever signal is configured in KillSignal=) as result.

           •   Behavior of notify is similar to exec; however, it is
               expected that the service sends a notification message
               via sd_notify(3) or an equivalent call when it has
               finished starting up. systemd will proceed with starting
               follow-up units after this notification message has been
               sent. If this option is used, NotifyAccess= (see below)
               should be set to open access to the notification socket
               provided by systemd. If NotifyAccess= is missing or set
               to none, it will be forcibly set to main.

           •   Behavior of idle is very similar to simple; however,
               actual execution of the service program is delayed until
               all active jobs are dispatched. This may be used to avoid
               interleaving of output of shell services with the status
               output on the console. Note that this type is useful only
               to improve console output, it is not useful as a general
               unit ordering tool, and the effect of this service type
               is subject to a 5s timeout, after which the service
               program is invoked anyway.

           It is generally recommended to use Type=simple for
           long-running services whenever possible, as it is the
           simplest and fastest option. However, as this service type
           won't propagate service start-up failures and doesn't allow
           ordering of other units against completion of initialization
           of the service (which for example is useful if clients need
           to connect to the service through some form of IPC, and the
           IPC channel is only established by the service itself — in
           contrast to doing this ahead of time through socket or bus
           activation or similar), it might not be sufficient for many
           cases. If so, notify or dbus (the latter only in case the
           service provides a D-Bus interface) are the preferred options
           as they allow service program code to precisely schedule when
           to consider the service started up successfully and when to
           proceed with follow-up units. The notify service type
           requires explicit support in the service codebase (as
           sd_notify() or an equivalent API needs to be invoked by the
           service at the appropriate time) — if it's not supported,
           then forking is an alternative: it supports the traditional
           UNIX service start-up protocol. Finally, exec might be an
           option for cases where it is enough to ensure the service
           binary is invoked, and where the service binary itself
           executes no or little initialization on its own (and its
           initialization is unlikely to fail). Note that using any type
           other than simple possibly delays the boot process, as the
           service manager needs to wait for service initialization to
           complete. It is hence recommended not to needlessly use any
           types other than simple. (Also note it is generally not
           recommended to use idle or oneshot for long-running
           services.)

       RemainAfterExit=
           Takes a boolean value that specifies whether the service
           shall be considered active even when all its processes
           exited. Defaults to no.

       GuessMainPID=
           Takes a boolean value that specifies whether systemd should
           try to guess the main PID of a service if it cannot be
           determined reliably. This option is ignored unless
           Type=forking is set and PIDFile= is unset because for the
           other types or with an explicitly configured PID file, the
           main PID is always known. The guessing algorithm might come
           to incorrect conclusions if a daemon consists of more than
           one process. If the main PID cannot be determined, failure
           detection and automatic restarting of a service will not work
           reliably. Defaults to yes.

       PIDFile=
           Takes a path referring to the PID file of the service. Usage
           of this option is recommended for services where Type= is set
           to forking. The path specified typically points to a file
           below /run/. If a relative path is specified it is hence
           prefixed with /run/. The service manager will read the PID of
           the main process of the service from this file after start-up
           of the service. The service manager will not write to the
           file configured here, although it will remove the file after
           the service has shut down if it still exists. The PID file
           does not need to be owned by a privileged user, but if it is
           owned by an unprivileged user additional safety restrictions
           are enforced: the file may not be a symlink to a file owned
           by a different user (neither directly nor indirectly), and
           the PID file must refer to a process already belonging to the
           service.

           Note that PID files should be avoided in modern projects. Use
           Type=notify or Type=simple where possible, which does not
           require use of PID files to determine the main process of a
           service and avoids needless forking.

       BusName=
           Takes a D-Bus destination name that this service shall use.
           This option is mandatory for services where Type= is set to
           dbus. It is recommended to always set this property if known
           to make it easy to map the service name to the D-Bus
           destination. In particular, systemctl
           service-log-level/service-log-target verbs make use of this.

       ExecStart=
           Commands with their arguments that are executed when this
           service is started. The value is split into zero or more
           command lines according to the rules described below (see
           section "Command Lines" below).

           Unless Type= is oneshot, exactly one command must be given.
           When Type=oneshot is used, zero or more commands may be
           specified. Commands may be specified by providing multiple
           command lines in the same directive, or alternatively, this
           directive may be specified more than once with the same
           effect. If the empty string is assigned to this option, the
           list of commands to start is reset, prior assignments of this
           option will have no effect. If no ExecStart= is specified,
           then the service must have RemainAfterExit=yes and at least
           one ExecStop= line set. (Services lacking both ExecStart= and
           ExecStop= are not valid.)

           For each of the specified commands, the first argument must
           be either an absolute path to an executable or a simple file
           name without any slashes. Optionally, this filename may be
           prefixed with a number of special characters:

           Table 1. Special executable prefixes
           ┌───────┬──────────────────────────┐
           │Prefix Effect                   │
           ├───────┼──────────────────────────┤
           │"@"    │ If the executable path   │
           │       │ is prefixed with "@",    │
           │       │ the second specified     │
           │       │ token will be passed as  │
           │       │ "argv[0]" to the         │
           │       │ executed process         │
           │       │ (instead of the actual   │
           │       │ filename), followed by   │
           │       │ the further arguments    │
           │       │ specified.               │
           ├───────┼──────────────────────────┤
           │"-"    │ If the executable path   │
           │       │ is prefixed with "-", an │
           │       │ exit code of the command │
           │       │ normally considered a    │
           │       │ failure (i.e. non-zero   │
           │       │ exit status or abnormal  │
           │       │ exit due to signal) is   │
           │       │ recorded, but has no     │
           │       │ further effect and is    │
           │       │ considered equivalent to │
           │       │ success.                 │
           ├───────┼──────────────────────────┤
           │":"    │ If the executable path   │
           │       │ is prefixed with ":",    │
           │       │ environment variable     │
           │       │ substitution (as         │
           │       │ described by the         │
           │       │ "Command Lines" section  │
           │       │ below) is not applied.   │
           ├───────┼──────────────────────────┤
           │"+"    │ If the executable path   │
           │       │ is prefixed with "+"     │
           │       │ then the process is      │
           │       │ executed with full       │
           │       │ privileges. In this mode │
           │       │ privilege restrictions   │
           │       │ configured with User=,   │
           │       │ Group=,                  │
           │       │ CapabilityBoundingSet=   │
           │       │ or the various file      │
           │       │ system namespacing       │
           │       │ options (such as         │
           │       │ PrivateDevices=,         │
           │       │ PrivateTmp=) are not     │
           │       │ applied to the invoked   │
           │       │ command line (but still  │
           │       │ affect any other         │
           │       │ ExecStart=, ExecStop=,   │
           │       │ ... lines).              │
           ├───────┼──────────────────────────┤
           │"!"    │ Similar to the "+"       │
           │       │ character discussed      │
           │       │ above this permits       │
           │       │ invoking command lines   │
           │       │ with elevated            │
           │       │ privileges. However,     │
           │       │ unlike "+" the "!"       │
           │       │ character exclusively    │
           │       │ alters the effect of     │
           │       │ User=, Group= and        │
           │       │ SupplementaryGroups=,    │
           │       │ i.e. only the stanzas    │
           │       │ that affect user and     │
           │       │ group credentials. Note  │
           │       │ that this setting may be │
           │       │ combined with            │
           │       │ DynamicUser=, in which   │
           │       │ case a dynamic           │
           │       │ user/group pair is       │
           │       │ allocated before the     │
           │       │ command is invoked, but  │
           │       │ credential changing is   │
           │       │ left to the executed     │
           │       │ process itself.          │
           ├───────┼──────────────────────────┤
           │"!!"   │ This prefix is very      │
           │       │ similar to "!", however  │
           │       │ it only has an effect on │
           │       │ systems lacking support  │
           │       │ for ambient process      │
           │       │ capabilities, i.e.       │
           │       │ without support for      │
           │       │ AmbientCapabilities=.    │
           │       │ It's intended to be used │
           │       │ for unit files that take │
           │       │ benefit of ambient       │
           │       │ capabilities to run      │
           │       │ processes with minimal   │
           │       │ privileges wherever      │
           │       │ possible while remaining │
           │       │ compatible with systems  │
           │       │ that lack ambient        │
           │       │ capabilities support.    │
           │       │ Note that when "!!" is   │
           │       │ used, and a system       │
           │       │ lacking ambient          │
           │       │ capability support is    │
           │       │ detected any configured  │
           │       │ SystemCallFilter= and    │
           │       │ CapabilityBoundingSet=   │
           │       │ stanzas are implicitly   │
           │       │ modified, in order to    │
           │       │ permit spawned processes │
           │       │ to drop credentials and  │
           │       │ capabilities themselves, │
           │       │ even if this is          │
           │       │ configured to not be     │
           │       │ allowed. Moreover, if    │
           │       │ this prefix is used and  │
           │       │ a system lacking ambient │
           │       │ capability support is    │
           │       │ detected                 │
           │       │ AmbientCapabilities=     │
           │       │ will be skipped and not  │
           │       │ be applied. On systems   │
           │       │ supporting ambient       │
           │       │ capabilities, "!!" has   │
           │       │ no effect and is         │
           │       │ redundant.               │
           └───────┴──────────────────────────┘
           "@", "-", ":", and one of "+"/"!"/"!!"  may be used together
           and they can appear in any order. However, only one of "+",
           "!", "!!"  may be used at a time. Note that these prefixes
           are also supported for the other command line settings, i.e.
           ExecStartPre=, ExecStartPost=, ExecReload=, ExecStop= and
           ExecStopPost=.

           If more than one command is specified, the commands are
           invoked sequentially in the order they appear in the unit
           file. If one of the commands fails (and is not prefixed with
           "-"), other lines are not executed, and the unit is
           considered failed.

           Unless Type=forking is set, the process started via this
           command line will be considered the main process of the
           daemon.

       ExecStartPre=, ExecStartPost=
           Additional commands that are executed before or after the
           command in ExecStart=, respectively. Syntax is the same as
           for ExecStart=, except that multiple command lines are
           allowed and the commands are executed one after the other,
           serially.

           If any of those commands (not prefixed with "-") fail, the
           rest are not executed and the unit is considered failed.

           ExecStart= commands are only run after all ExecStartPre=
           commands that were not prefixed with a "-" exit successfully.

           ExecStartPost= commands are only run after the commands
           specified in ExecStart= have been invoked successfully, as
           determined by Type= (i.e. the process has been started for
           Type=simple or Type=idle, the last ExecStart= process exited
           successfully for Type=oneshot, the initial process exited
           successfully for Type=forking, "READY=1" is sent for
           Type=notify, or the BusName= has been taken for Type=dbus).

           Note that ExecStartPre= may not be used to start long-running
           processes. All processes forked off by processes invoked via
           ExecStartPre= will be killed before the next service process
           is run.

           Note that if any of the commands specified in ExecStartPre=,
           ExecStart=, or ExecStartPost= fail (and are not prefixed with
           "-", see above) or time out before the service is fully up,
           execution continues with commands specified in ExecStopPost=,
           the commands in ExecStop= are skipped.

           Note that the execution of ExecStartPost= is taken into
           account for the purpose of Before=/After= ordering
           constraints.

       ExecCondition=
           Optional commands that are executed before the command(s) in
           ExecStartPre=. Syntax is the same as for ExecStart=, except
           that multiple command lines are allowed and the commands are
           executed one after the other, serially.

           The behavior is like an ExecStartPre= and condition check
           hybrid: when an ExecCondition= command exits with exit code 1
           through 254 (inclusive), the remaining commands are skipped
           and the unit is not marked as failed. However, if an
           ExecCondition= command exits with 255 or abnormally (e.g.
           timeout, killed by a signal, etc.), the unit will be
           considered failed (and remaining commands will be skipped).
           Exit code of 0 or those matching SuccessExitStatus= will
           continue execution to the next command(s).

           The same recommendations about not running long-running
           processes in ExecStartPre= also applies to ExecCondition=.
           ExecCondition= will also run the commands in ExecStopPost=,
           as part of stopping the service, in the case of any non-zero
           or abnormal exits, like the ones described above.

       ExecReload=
           Commands to execute to trigger a configuration reload in the
           service. This argument takes multiple command lines,
           following the same scheme as described for ExecStart= above.
           Use of this setting is optional. Specifier and environment
           variable substitution is supported here following the same
           scheme as for ExecStart=.

           One additional, special environment variable is set: if
           known, $MAINPID is set to the main process of the daemon, and
           may be used for command lines like the following:

               ExecReload=kill -HUP $MAINPID

           Note however that reloading a daemon by sending a signal (as
           with the example line above) is usually not a good choice,
           because this is an asynchronous operation and hence not
           suitable to order reloads of multiple services against each
           other. It is strongly recommended to set ExecReload= to a
           command that not only triggers a configuration reload of the
           daemon, but also synchronously waits for it to complete. For
           example, dbus-broker(1) uses the following:

               ExecReload=busctl call org.freedesktop.DBus \
                       /org/freedesktop/DBus org.freedesktop.DBus \
                       ReloadConfig

       ExecStop=
           Commands to execute to stop the service started via
           ExecStart=. This argument takes multiple command lines,
           following the same scheme as described for ExecStart= above.
           Use of this setting is optional. After the commands
           configured in this option are run, it is implied that the
           service is stopped, and any processes remaining for it are
           terminated according to the KillMode= setting (see
           systemd.kill(5)). If this option is not specified, the
           process is terminated by sending the signal specified in
           KillSignal= or RestartKillSignal= when service stop is
           requested. Specifier and environment variable substitution is
           supported (including $MAINPID, see above).

           Note that it is usually not sufficient to specify a command
           for this setting that only asks the service to terminate (for
           example, by sending some form of termination signal to it),
           but does not wait for it to do so. Since the remaining
           processes of the services are killed according to KillMode=
           and KillSignal= or RestartKillSignal= as described above
           immediately after the command exited, this may not result in
           a clean stop. The specified command should hence be a
           synchronous operation, not an asynchronous one.

           Note that the commands specified in ExecStop= are only
           executed when the service started successfully first. They
           are not invoked if the service was never started at all, or
           in case its start-up failed, for example because any of the
           commands specified in ExecStart=, ExecStartPre= or
           ExecStartPost= failed (and weren't prefixed with "-", see
           above) or timed out. Use ExecStopPost= to invoke commands
           when a service failed to start up correctly and is shut down
           again. Also note that the stop operation is always performed
           if the service started successfully, even if the processes in
           the service terminated on their own or were killed. The stop
           commands must be prepared to deal with that case.  $MAINPID
           will be unset if systemd knows that the main process exited
           by the time the stop commands are called.

           Service restart requests are implemented as stop operations
           followed by start operations. This means that ExecStop= and
           ExecStopPost= are executed during a service restart
           operation.

           It is recommended to use this setting for commands that
           communicate with the service requesting clean termination.
           For post-mortem clean-up steps use ExecStopPost= instead.

       ExecStopPost=
           Additional commands that are executed after the service is
           stopped. This includes cases where the commands configured in
           ExecStop= were used, where the service does not have any
           ExecStop= defined, or where the service exited unexpectedly.
           This argument takes multiple command lines, following the
           same scheme as described for ExecStart=. Use of these
           settings is optional. Specifier and environment variable
           substitution is supported. Note that – unlike ExecStop= –
           commands specified with this setting are invoked when a
           service failed to start up correctly and is shut down again.

           It is recommended to use this setting for clean-up operations
           that shall be executed even when the service failed to start
           up correctly. Commands configured with this setting need to
           be able to operate even if the service failed starting up
           half-way and left incompletely initialized data around. As
           the service's processes have been terminated already when the
           commands specified with this setting are executed they should
           not attempt to communicate with them.

           Note that all commands that are configured with this setting
           are invoked with the result code of the service, as well as
           the main process' exit code and status, set in the
           $SERVICE_RESULT, $EXIT_CODE and $EXIT_STATUS environment
           variables, see systemd.exec(5) for details.

           Note that the execution of ExecStopPost= is taken into
           account for the purpose of Before=/After= ordering
           constraints.

       RestartSec=
           Configures the time to sleep before restarting a service (as
           configured with Restart=). Takes a unit-less value in
           seconds, or a time span value such as "5min 20s". Defaults to
           100ms.

       TimeoutStartSec=
           Configures the time to wait for start-up. If a daemon service
           does not signal start-up completion within the configured
           time, the service will be considered failed and will be shut
           down again. The precise action depends on the
           TimeoutStartFailureMode= option. Takes a unit-less value in
           seconds, or a time span value such as "5min 20s". Pass
           "infinity" to disable the timeout logic. Defaults to
           DefaultTimeoutStartSec= from the manager configuration file,
           except when Type=oneshot is used, in which case the timeout
           is disabled by default (see systemd-system.conf(5)).

           If a service of Type=notify sends "EXTEND_TIMEOUT_USEC=...",
           this may cause the start time to be extended beyond
           TimeoutStartSec=. The first receipt of this message must
           occur before TimeoutStartSec= is exceeded, and once the start
           time has extended beyond TimeoutStartSec=, the service
           manager will allow the service to continue to start, provided
           the service repeats "EXTEND_TIMEOUT_USEC=..."  within the
           interval specified until the service startup status is
           finished by "READY=1". (see sd_notify(3)).

       TimeoutStopSec=
           This option serves two purposes. First, it configures the
           time to wait for each ExecStop= command. If any of them times
           out, subsequent ExecStop= commands are skipped and the
           service will be terminated by SIGTERM. If no ExecStop=
           commands are specified, the service gets the SIGTERM
           immediately. This default behavior can be changed by the
           TimeoutStopFailureMode= option. Second, it configures the
           time to wait for the service itself to stop. If it doesn't
           terminate in the specified time, it will be forcibly
           terminated by SIGKILL (see KillMode= in systemd.kill(5)).
           Takes a unit-less value in seconds, or a time span value such
           as "5min 20s". Pass "infinity" to disable the timeout logic.
           Defaults to DefaultTimeoutStopSec= from the manager
           configuration file (see systemd-system.conf(5)).

           If a service of Type=notify sends "EXTEND_TIMEOUT_USEC=...",
           this may cause the stop time to be extended beyond
           TimeoutStopSec=. The first receipt of this message must occur
           before TimeoutStopSec= is exceeded, and once the stop time
           has extended beyond TimeoutStopSec=, the service manager will
           allow the service to continue to stop, provided the service
           repeats "EXTEND_TIMEOUT_USEC=..."  within the interval
           specified, or terminates itself (see sd_notify(3)).

       TimeoutAbortSec=
           This option configures the time to wait for the service to
           terminate when it was aborted due to a watchdog timeout (see
           WatchdogSec=). If the service has a short TimeoutStopSec=
           this option can be used to give the system more time to write
           a core dump of the service. Upon expiration the service will
           be forcibly terminated by SIGKILL (see KillMode= in
           systemd.kill(5)). The core file will be truncated in this
           case. Use TimeoutAbortSec= to set a sensible timeout for the
           core dumping per service that is large enough to write all
           expected data while also being short enough to handle the
           service failure in due time.

           Takes a unit-less value in seconds, or a time span value such
           as "5min 20s". Pass an empty value to skip the dedicated
           watchdog abort timeout handling and fall back
           TimeoutStopSec=. Pass "infinity" to disable the timeout
           logic. Defaults to DefaultTimeoutAbortSec= from the manager
           configuration file (see systemd-system.conf(5)).

           If a service of Type=notify handles SIGABRT itself (instead
           of relying on the kernel to write a core dump) it can send
           "EXTEND_TIMEOUT_USEC=..."  to extended the abort time beyond
           TimeoutAbortSec=. The first receipt of this message must
           occur before TimeoutAbortSec= is exceeded, and once the abort
           time has extended beyond TimeoutAbortSec=, the service
           manager will allow the service to continue to abort, provided
           the service repeats "EXTEND_TIMEOUT_USEC=..."  within the
           interval specified, or terminates itself (see sd_notify(3)).

       TimeoutSec=
           A shorthand for configuring both TimeoutStartSec= and
           TimeoutStopSec= to the specified value.

       TimeoutStartFailureMode=, TimeoutStopFailureMode=
           These options configure the action that is taken in case a
           daemon service does not signal start-up within its configured
           TimeoutStartSec=, respectively if it does not stop within
           TimeoutStopSec=. Takes one of terminate, abort and kill. Both
           options default to terminate.

           If terminate is set the service will be gracefully terminated
           by sending the signal specified in KillSignal= (defaults to
           SIGTERM, see systemd.kill(5)). If the service does not
           terminate the FinalKillSignal= is sent after TimeoutStopSec=.
           If abort is set, WatchdogSignal= is sent instead and
           TimeoutAbortSec= applies before sending FinalKillSignal=.
           This setting may be used to analyze services that fail to
           start-up or shut-down intermittently. By using kill the
           service is immediately terminated by sending FinalKillSignal=
           without any further timeout. This setting can be used to
           expedite the shutdown of failing services.

       RuntimeMaxSec=
           Configures a maximum time for the service to run. If this is
           used and the service has been active for longer than the
           specified time it is terminated and put into a failure state.
           Note that this setting does not have any effect on
           Type=oneshot services, as they terminate immediately after
           activation completed. Pass "infinity" (the default) to
           configure no runtime limit.

           If a service of Type=notify sends "EXTEND_TIMEOUT_USEC=...",
           this may cause the runtime to be extended beyond
           RuntimeMaxSec=. The first receipt of this message must occur
           before RuntimeMaxSec= is exceeded, and once the runtime has
           extended beyond RuntimeMaxSec=, the service manager will
           allow the service to continue to run, provided the service
           repeats "EXTEND_TIMEOUT_USEC=..."  within the interval
           specified until the service shutdown is achieved by
           "STOPPING=1" (or termination). (see sd_notify(3)).

       WatchdogSec=
           Configures the watchdog timeout for a service. The watchdog
           is activated when the start-up is completed. The service must
           call sd_notify(3) regularly with "WATCHDOG=1" (i.e. the
           "keep-alive ping"). If the time between two such calls is
           larger than the configured time, then the service is placed
           in a failed state and it will be terminated with SIGABRT (or
           the signal specified by WatchdogSignal=). By setting Restart=
           to on-failure, on-watchdog, on-abnormal or always, the
           service will be automatically restarted. The time configured
           here will be passed to the executed service process in the
           WATCHDOG_USEC= environment variable. This allows daemons to
           automatically enable the keep-alive pinging logic if watchdog
           support is enabled for the service. If this option is used,
           NotifyAccess= (see below) should be set to open access to the
           notification socket provided by systemd. If NotifyAccess= is
           not set, it will be implicitly set to main. Defaults to 0,
           which disables this feature. The service can check whether
           the service manager expects watchdog keep-alive
           notifications. See sd_watchdog_enabled(3) for details.
           sd_event_set_watchdog(3) may be used to enable automatic
           watchdog notification support.

       Restart=
           Configures whether the service shall be restarted when the
           service process exits, is killed, or a timeout is reached.
           The service process may be the main service process, but it
           may also be one of the processes specified with
           ExecStartPre=, ExecStartPost=, ExecStop=, ExecStopPost=, or
           ExecReload=. When the death of the process is a result of
           systemd operation (e.g. service stop or restart), the service
           will not be restarted. Timeouts include missing the watchdog
           "keep-alive ping" deadline and a service start, reload, and
           stop operation timeouts.

           Takes one of no, on-success, on-failure, on-abnormal,
           on-watchdog, on-abort, or always. If set to no (the default),
           the service will not be restarted. If set to on-success, it
           will be restarted only when the service process exits
           cleanly. In this context, a clean exit means any of the
           following:

           •   exit code of 0;

           •   for types other than Type=oneshot, one of the signals
               SIGHUP, SIGINT, SIGTERM, or SIGPIPE;

           •   exit statuses and signals specified in
               SuccessExitStatus=.

           If set to on-failure, the service will be restarted when the
           process exits with a non-zero exit code, is terminated by a
           signal (including on core dump, but excluding the
           aforementioned four signals), when an operation (such as
           service reload) times out, and when the configured watchdog
           timeout is triggered. If set to on-abnormal, the service will
           be restarted when the process is terminated by a signal
           (including on core dump, excluding the aforementioned four
           signals), when an operation times out, or when the watchdog
           timeout is triggered. If set to on-abort, the service will be
           restarted only if the service process exits due to an
           uncaught signal not specified as a clean exit status. If set
           to on-watchdog, the service will be restarted only if the
           watchdog timeout for the service expires. If set to always,
           the service will be restarted regardless of whether it exited
           cleanly or not, got terminated abnormally by a signal, or hit
           a timeout.

           Table 2. Exit causes and the effect of the Restart= settings
           ┌──────────────┬────┬────────┬────────────┬────────────┬─────────────┬──────────┬─────────────┐
           │Restart       no always on-success on-failure on-abnormal on-abort on-watchdog │
           │settings/Exit │    │        │            │            │             │          │             │
           │causes        │    │        │            │            │             │          │             │
           ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
           │Clean exit    │    │ X      │ X          │            │             │          │             │
           │code or       │    │        │            │            │             │          │             │
           │signal        │    │        │            │            │             │          │             │
           ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
           │Unclean exit  │    │ X      │            │ X          │             │          │             │
           │code          │    │        │            │            │             │          │             │
           ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
           │Unclean       │    │ X      │            │ X          │ X           │ X        │             │
           │signal        │    │        │            │            │             │          │             │
           ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
           │Timeout       │    │ X      │            │ X          │ X           │          │             │
           ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
           │Watchdog      │    │ X      │            │ X          │ X           │          │ X           │
           └──────────────┴────┴────────┴────────────┴────────────┴─────────────┴──────────┴─────────────┘
           As exceptions to the setting above, the service will not be
           restarted if the exit code or signal is specified in
           RestartPreventExitStatus= (see below) or the service is
           stopped with systemctl stop or an equivalent operation. Also,
           the services will always be restarted if the exit code or
           signal is specified in RestartForceExitStatus= (see below).

           Note that service restart is subject to unit start rate
           limiting configured with StartLimitIntervalSec= and
           StartLimitBurst=, see systemd.unit(5) for details. A
           restarted service enters the failed state only after the
           start limits are reached.

           Setting this to on-failure is the recommended choice for
           long-running services, in order to increase reliability by
           attempting automatic recovery from errors. For services that
           shall be able to terminate on their own choice (and avoid
           immediate restarting), on-abnormal is an alternative choice.

       SuccessExitStatus=
           Takes a list of exit status definitions that, when returned
           by the main service process, will be considered successful
           termination, in addition to the normal successful exit status
           0 and, except for Type=oneshot, the signals SIGHUP, SIGINT,
           SIGTERM, and SIGPIPE. Exit status definitions can be numeric
           termination statuses, termination status names, or
           termination signal names, separated by spaces. See the
           Process Exit Codes section in systemd.exec(5) for a list of
           termination status names (for this setting only the part
           without the "EXIT_" or "EX_" prefix should be used). See
           signal(7) for a list of signal names.

           Note that this setting does not change the mapping between
           numeric exit statuses and their names, i.e. regardless how
           this setting is used 0 will still be mapped to "SUCCESS" (and
           thus typically shown as "0/SUCCESS" in tool outputs) and 1 to
           "FAILURE" (and thus typically shown as "1/FAILURE"), and so
           on. It only controls what happens as effect of these exit
           statuses, and how it propagates to the state of the service
           as a whole.

           This option may appear more than once, in which case the list
           of successful exit statuses is merged. If the empty string is
           assigned to this option, the list is reset, all prior
           assignments of this option will have no effect.

           Example 1. A service with the SuccessExitStatus= setting

               SuccessExitStatus=TEMPFAIL 250 SIGKILL

           Exit status 75 (TEMPFAIL), 250, and the termination signal
           SIGKILL are considered clean service terminations.

           Note: systemd-analyze exit-status may be used to list exit
           statuses and translate between numerical status values and
           names.

       RestartPreventExitStatus=
           Takes a list of exit status definitions that, when returned
           by the main service process, will prevent automatic service
           restarts, regardless of the restart setting configured with
           Restart=. Exit status definitions can either be numeric exit
           codes or termination signal names, and are separated by
           spaces. Defaults to the empty list, so that, by default, no
           exit status is excluded from the configured restart logic.
           For example:

               RestartPreventExitStatus=1 6 SIGABRT

           ensures that exit codes 1 and 6 and the termination signal
           SIGABRT will not result in automatic service restarting. This
           option may appear more than once, in which case the list of
           restart-preventing statuses is merged. If the empty string is
           assigned to this option, the list is reset and all prior
           assignments of this option will have no effect.

           Note that this setting has no effect on processes configured
           via ExecStartPre=, ExecStartPost=, ExecStop=, ExecStopPost=
           or ExecReload=, but only on the main service process, i.e.
           either the one invoked by ExecStart= or (depending on Type=,
           PIDFile=, ...) the otherwise configured main process.

       RestartForceExitStatus=
           Takes a list of exit status definitions that, when returned
           by the main service process, will force automatic service
           restarts, regardless of the restart setting configured with
           Restart=. The argument format is similar to
           RestartPreventExitStatus=.

       RootDirectoryStartOnly=
           Takes a boolean argument. If true, the root directory, as
           configured with the RootDirectory= option (see
           systemd.exec(5) for more information), is only applied to the
           process started with ExecStart=, and not to the various other
           ExecStartPre=, ExecStartPost=, ExecReload=, ExecStop=, and
           ExecStopPost= commands. If false, the setting is applied to
           all configured commands the same way. Defaults to false.

       NonBlocking=
           Set the O_NONBLOCK flag for all file descriptors passed via
           socket-based activation. If true, all file descriptors >= 3
           (i.e. all except stdin, stdout, stderr), excluding those
           passed in via the file descriptor storage logic (see
           FileDescriptorStoreMax= for details), will have the
           O_NONBLOCK flag set and hence are in non-blocking mode. This
           option is only useful in conjunction with a socket unit, as
           described in systemd.socket(5) and has no effect on file
           descriptors which were previously saved in the
           file-descriptor store for example. Defaults to false.

       NotifyAccess=
           Controls access to the service status notification socket, as
           accessible via the sd_notify(3) call. Takes one of none (the
           default), main, exec or all. If none, no daemon status
           updates are accepted from the service processes, all status
           update messages are ignored. If main, only service updates
           sent from the main process of the service are accepted. If
           exec, only service updates sent from any of the main or
           control processes originating from one of the Exec*= commands
           are accepted. If all, all services updates from all members
           of the service's control group are accepted. This option
           should be set to open access to the notification socket when
           using Type=notify or WatchdogSec= (see above). If those
           options are used but NotifyAccess= is not configured, it will
           be implicitly set to main.

           Note that sd_notify() notifications may be attributed to
           units correctly only if either the sending process is still
           around at the time PID 1 processes the message, or if the
           sending process is explicitly runtime-tracked by the service
           manager. The latter is the case if the service manager
           originally forked off the process, i.e. on all processes that
           match main or exec. Conversely, if an auxiliary process of
           the unit sends an sd_notify() message and immediately exits,
           the service manager might not be able to properly attribute
           the message to the unit, and thus will ignore it, even if
           NotifyAccess=all is set for it.

           Hence, to eliminate all race conditions involving lookup of
           the client's unit and attribution of notifications to units
           correctly, sd_notify_barrier() may be used. This call acts as
           a synchronization point and ensures all notifications sent
           before this call have been picked up by the service manager
           when it returns successfully. Use of sd_notify_barrier() is
           needed for clients which are not invoked by the service
           manager, otherwise this synchronization mechanism is
           unnecessary for attribution of notifications to the unit.

       Sockets=
           Specifies the name of the socket units this service shall
           inherit socket file descriptors from when the service is
           started. Normally, it should not be necessary to use this
           setting, as all socket file descriptors whose unit shares the
           same name as the service (subject to the different unit name
           suffix of course) are passed to the spawned process.

           Note that the same socket file descriptors may be passed to
           multiple processes simultaneously. Also note that a different
           service may be activated on incoming socket traffic than the
           one which is ultimately configured to inherit the socket file
           descriptors. Or, in other words: the Service= setting of
           .socket units does not have to match the inverse of the
           Sockets= setting of the .service it refers to.

           This option may appear more than once, in which case the list
           of socket units is merged. Note that once set, clearing the
           list of sockets again (for example, by assigning the empty
           string to this option) is not supported.

       FileDescriptorStoreMax=
           Configure how many file descriptors may be stored in the
           service manager for the service using
           sd_pid_notify_with_fds(3)'s "FDSTORE=1" messages. This is
           useful for implementing services that can restart after an
           explicit request or a crash without losing state. Any open
           sockets and other file descriptors which should not be closed
           during the restart may be stored this way. Application state
           can either be serialized to a file in /run/, or better,
           stored in a memfd_create(2) memory file descriptor. Defaults
           to 0, i.e. no file descriptors may be stored in the service
           manager. All file descriptors passed to the service manager
           from a specific service are passed back to the service's main
           process on the next service restart (see sd_listen_fds(3) for
           details about the precise protocol used and the order in
           which the file descriptors are passed). Any file descriptors
           passed to the service manager are automatically closed when
           POLLHUP or POLLERR is seen on them, or when the service is
           fully stopped and no job is queued or being executed for it.
           If this option is used, NotifyAccess= (see above) should be
           set to open access to the notification socket provided by
           systemd. If NotifyAccess= is not set, it will be implicitly
           set to main.

       USBFunctionDescriptors=
           Configure the location of a file containing USB FunctionFS[2]
           descriptors, for implementation of USB gadget functions. This
           is used only in conjunction with a socket unit with
           ListenUSBFunction= configured. The contents of this file are
           written to the ep0 file after it is opened.

       USBFunctionStrings=
           Configure the location of a file containing USB FunctionFS
           strings. Behavior is similar to USBFunctionDescriptors=
           above.

       OOMPolicy=
           Configure the Out-Of-Memory (OOM) killer policy. On Linux,
           when memory becomes scarce the kernel might decide to kill a
           running process in order to free up memory and reduce memory
           pressure. This setting takes one of continue, stop or kill.
           If set to continue and a process of the service is killed by
           the kernel's OOM killer this is logged but the service
           continues running. If set to stop the event is logged but the
           service is terminated cleanly by the service manager. If set
           to kill and one of the service's processes is killed by the
           OOM killer the kernel is instructed to kill all remaining
           processes of the service, too. Defaults to the setting
           DefaultOOMPolicy= in systemd-system.conf(5) is set to, except
           for services where Delegate= is turned on, where it defaults
           to continue.

           Use the OOMScoreAdjust= setting to configure whether
           processes of the unit shall be considered preferred or less
           preferred candidates for process termination by the Linux OOM
           killer logic. See systemd.exec(5) for details.

       Check systemd.exec(5) and systemd.kill(5) for more settings.

COMMAND LINES         top

       This section describes command line parsing and variable and
       specifier substitutions for ExecStart=, ExecStartPre=,
       ExecStartPost=, ExecReload=, ExecStop=, and ExecStopPost=
       options.

       Multiple command lines may be concatenated in a single directive
       by separating them with semicolons (these semicolons must be
       passed as separate words). Lone semicolons may be escaped as
       "\;".

       Each command line is unquoted using the rules described in
       "Quoting" section in systemd.syntax(7). The first item becomes
       the command to execute, and the subsequent items the arguments.

       This syntax is inspired by shell syntax, but only the
       meta-characters and expansions described in the following
       paragraphs are understood, and the expansion of variables is
       different. Specifically, redirection using "<", "<<", ">", and
       ">>", pipes using "|", running programs in the background using
       "&", and other elements of shell syntax are not supported.

       The command to execute may contain spaces, but control characters
       are not allowed.

       The command line accepts "%" specifiers as described in
       systemd.unit(5).

       Basic environment variable substitution is supported. Use
       "${FOO}" as part of a word, or as a word of its own, on the
       command line, in which case it will be erased and replaced by the
       exact value of the environment variable (if any) including all
       whitespace it contains, always resulting in exactly a single
       argument. Use "$FOO" as a separate word on the command line, in
       which case it will be replaced by the value of the environment
       variable split at whitespace, resulting in zero or more
       arguments. For this type of expansion, quotes are respected when
       splitting into words, and afterwards removed.

       If the command is not a full (absolute) path, it will be resolved
       to a full path using a fixed search path determined at
       compilation time. Searched directories include /usr/local/bin/,
       /usr/bin/, /bin/ on systems using split /usr/bin/ and /bin/
       directories, and their sbin/ counterparts on systems using split
       bin/ and sbin/. It is thus safe to use just the executable name
       in case of executables located in any of the "standard"
       directories, and an absolute path must be used in other cases.
       Using an absolute path is recommended to avoid ambiguity. Hint:
       this search path may be queried using systemd-path
       search-binaries-default.

       Example:

           Environment="ONE=one" 'TWO=two two'
           ExecStart=echo $ONE $TWO ${TWO}

       This will execute /bin/echo with four arguments: "one", "two",
       "two", and "two two".

       Example:

           Environment=ONE='one' "TWO='two two' too" THREE=
           ExecStart=/bin/echo ${ONE} ${TWO} ${THREE}
           ExecStart=/bin/echo $ONE $TWO $THREE

       This results in /bin/echo being called twice, the first time with
       arguments "'one'", "'two two' too", "", and the second time with
       arguments "one", "two two", "too".

       To pass a literal dollar sign, use "$$". Variables whose value is
       not known at expansion time are treated as empty strings. Note
       that the first argument (i.e. the program to execute) may not be
       a variable.

       Variables to be used in this fashion may be defined through
       Environment= and EnvironmentFile=. In addition, variables listed
       in the section "Environment variables in spawned processes" in
       systemd.exec(5), which are considered "static configuration", may
       be used (this includes e.g.  $USER, but not $TERM).

       Note that shell command lines are not directly supported. If
       shell command lines are to be used, they need to be passed
       explicitly to a shell implementation of some kind. Example:

           ExecStart=sh -c 'dmesg | tac'

       Example:

           ExecStart=echo one ; echo "two two"

       This will execute echo two times, each time with one argument:
       "one" and "two two", respectively. Because two commands are
       specified, Type=oneshot must be used.

       Example:

           ExecStart=echo / >/dev/null & \; \
           ls

       This will execute echo with five arguments: "/", ">/dev/null",
       "&", ";", and "ls".

EXAMPLES         top

       Example 2. Simple service

       The following unit file creates a service that will execute
       /usr/sbin/foo-daemon. Since no Type= is specified, the default
       Type=simple will be assumed. systemd will assume the unit to be
       started immediately after the program has begun executing.

           [Unit]
           Description=Foo

           [Service]
           ExecStart=/usr/sbin/foo-daemon

           [Install]
           WantedBy=multi-user.target

       Note that systemd assumes here that the process started by
       systemd will continue running until the service terminates. If
       the program daemonizes itself (i.e. forks), please use
       Type=forking instead.

       Since no ExecStop= was specified, systemd will send SIGTERM to
       all processes started from this service, and after a timeout also
       SIGKILL. This behavior can be modified, see systemd.kill(5) for
       details.

       Note that this unit type does not include any type of
       notification when a service has completed initialization. For
       this, you should use other unit types, such as Type=notify if the
       service understands systemd's notification protocol, Type=forking
       if the service can background itself or Type=dbus if the unit
       acquires a DBus name once initialization is complete. See below.

       Example 3. Oneshot service

       Sometimes, units should just execute an action without keeping
       active processes, such as a filesystem check or a cleanup action
       on boot. For this, Type=oneshot exists. Units of this type will
       wait until the process specified terminates and then fall back to
       being inactive. The following unit will perform a cleanup action:

           [Unit]
           Description=Cleanup old Foo data

           [Service]
           Type=oneshot
           ExecStart=/usr/sbin/foo-cleanup

           [Install]
           WantedBy=multi-user.target

       Note that systemd will consider the unit to be in the state
       "starting" until the program has terminated, so ordered
       dependencies will wait for the program to finish before starting
       themselves. The unit will revert to the "inactive" state after
       the execution is done, never reaching the "active" state. That
       means another request to start the unit will perform the action
       again.

       Type=oneshot are the only service units that may have more than
       one ExecStart= specified. For units with multiple commands
       (Type=oneshot), all commands will be run again.

       For Type=oneshot, Restart=always and Restart=on-success are not
       allowed.

       Example 4. Stoppable oneshot service

       Similarly to the oneshot services, there are sometimes units that
       need to execute a program to set up something and then execute
       another to shut it down, but no process remains active while they
       are considered "started". Network configuration can sometimes
       fall into this category. Another use case is if a oneshot service
       shall not be executed each time when they are pulled in as a
       dependency, but only the first time.

       For this, systemd knows the setting RemainAfterExit=yes, which
       causes systemd to consider the unit to be active if the start
       action exited successfully. This directive can be used with all
       types, but is most useful with Type=oneshot and Type=simple. With
       Type=oneshot, systemd waits until the start action has completed
       before it considers the unit to be active, so dependencies start
       only after the start action has succeeded. With Type=simple,
       dependencies will start immediately after the start action has
       been dispatched. The following unit provides an example for a
       simple static firewall.

           [Unit]
           Description=Simple firewall

           [Service]
           Type=oneshot
           RemainAfterExit=yes
           ExecStart=/usr/local/sbin/simple-firewall-start
           ExecStop=/usr/local/sbin/simple-firewall-stop

           [Install]
           WantedBy=multi-user.target

       Since the unit is considered to be running after the start action
       has exited, invoking systemctl start on that unit again will
       cause no action to be taken.

       Example 5. Traditional forking services

       Many traditional daemons/services background (i.e. fork,
       daemonize) themselves when starting. Set Type=forking in the
       service's unit file to support this mode of operation. systemd
       will consider the service to be in the process of initialization
       while the original program is still running. Once it exits
       successfully and at least a process remains (and
       RemainAfterExit=no), the service is considered started.

       Often, a traditional daemon only consists of one process.
       Therefore, if only one process is left after the original process
       terminates, systemd will consider that process the main process
       of the service. In that case, the $MAINPID variable will be
       available in ExecReload=, ExecStop=, etc.

       In case more than one process remains, systemd will be unable to
       determine the main process, so it will not assume there is one.
       In that case, $MAINPID will not expand to anything. However, if
       the process decides to write a traditional PID file, systemd will
       be able to read the main PID from there. Please set PIDFile=
       accordingly. Note that the daemon should write that file before
       finishing with its initialization. Otherwise, systemd might try
       to read the file before it exists.

       The following example shows a simple daemon that forks and just
       starts one process in the background:

           [Unit]
           Description=Some simple daemon

           [Service]
           Type=forking
           ExecStart=/usr/sbin/my-simple-daemon -d

           [Install]
           WantedBy=multi-user.target

       Please see systemd.kill(5) for details on how you can influence
       the way systemd terminates the service.

       Example 6. DBus services

       For services that acquire a name on the DBus system bus, use
       Type=dbus and set BusName= accordingly. The service should not
       fork (daemonize). systemd will consider the service to be
       initialized once the name has been acquired on the system bus.
       The following example shows a typical DBus service:

           [Unit]
           Description=Simple DBus service

           [Service]
           Type=dbus
           BusName=org.example.simple-dbus-service
           ExecStart=/usr/sbin/simple-dbus-service

           [Install]
           WantedBy=multi-user.target

       For bus-activatable services, do not include a [Install] section
       in the systemd service file, but use the SystemdService= option
       in the corresponding DBus service file, for example
       (/usr/share/dbus-1/system-services/org.example.simple-dbus-service.service):

           [D-BUS Service]
           Name=org.example.simple-dbus-service
           Exec=/usr/sbin/simple-dbus-service
           User=root
           SystemdService=simple-dbus-service.service

       Please see systemd.kill(5) for details on how you can influence
       the way systemd terminates the service.

       Example 7. Services that notify systemd about their
       initialization

       Type=simple services are really easy to write, but have the major
       disadvantage of systemd not being able to tell when
       initialization of the given service is complete. For this reason,
       systemd supports a simple notification protocol that allows
       daemons to make systemd aware that they are done initializing.
       Use Type=notify for this. A typical service file for such a
       daemon would look like this:

           [Unit]
           Description=Simple notifying service

           [Service]
           Type=notify
           ExecStart=/usr/sbin/simple-notifying-service

           [Install]
           WantedBy=multi-user.target

       Note that the daemon has to support systemd's notification
       protocol, else systemd will think the service has not started yet
       and kill it after a timeout. For an example of how to update
       daemons to support this protocol transparently, take a look at
       sd_notify(3). systemd will consider the unit to be in the
       'starting' state until a readiness notification has arrived.

       Please see systemd.kill(5) for details on how you can influence
       the way systemd terminates the service.

SEE ALSO         top

       systemd(1), systemctl(1), systemd-system.conf(5),
       systemd.unit(5), systemd.exec(5), systemd.resource-control(5),
       systemd.kill(5), systemd.directives(7), systemd-run(1)

NOTES         top

        1. Incompatibilities with SysV
           https://www.freedesktop.org/wiki/Software/systemd/Incompatibilities

        2. USB FunctionFS
           https://www.kernel.org/doc/Documentation/usb/functionfs.txt

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-27.)  If you discover 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 249                                           SYSTEMD.SERVICE(5)

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