systemd Developer Lennart Poettering lennart@poettering.net systemd.service 5 systemd.service Service unit configuration systemd.service 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.unit5 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.exec5, which define the execution environment the commands are executed in, and in systemd.kill5 which define the way the processes of the service are terminated. Unless DefaultDependencies= is set to false, service units will implicitly have dependencies of type Requires= and 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. 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 document. 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.exec5 and systemd.kill5. 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, forking, oneshot, dbus, notify or idle. If set to simple (the default value if BusName= is not specified) 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 daemon is started up (e.g. sockets set up by systemd, via socket activation), as systemd will immediately proceed starting follow-up units. 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 set up. The child continues to run as the main daemon process. This is the behavior of traditional UNIX daemons. If this setting is used, it is recommended to also use the PIDFile= option, so that systemd can identify the main process of the daemon. systemd will proceed starting follow-up units as soon as the parent process exits. Behavior of oneshot is similar to simple, however it is expected that the process has to exit before systemd starts follow-up units. RemainAfterExit= is particularly useful for this type of service. Behavior of dbus is similar to simple, however it is expected that the daemon acquires a name on the D-Bus bus, as configured by BusName=. systemd will proceed 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. Behavior of notify is similar to simple, however it is expected that the daemon sends a notification message via sd_notify3 or an equivalent call when it finished starting up. systemd will proceed 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 not set, it will be implicitly set to main. Behavior of idle is very similar to simple, however actual execution of the service binary is delayed until all jobs are dispatched. This may be used to avoid interleaving of output of shell services with the status output on the console. 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 an absolute file name pointing to the PID file of this daemon. Use of this option is recommended for services where Type= is set to forking. systemd will read the PID of the main process of the daemon after start-up of the service. systemd will not write to the file configured here. BusName= Takes a D-Bus bus name, that this service is reachable as. This option is mandatory for services where Type= is set to dbus, but its use is otherwise recommended as well if the process takes a name on the D-Bus bus. ExecStart= Takes a command line that is executed when this service shall be started up. The first token of the command line must be an absolute file name, then followed by arguments for the process. It is mandatory to set this option for all services. This option may not be specified more than once, except when Type=oneshot is used in which case more than one ExecStart= line is accepted which are then invoked one by one, sequentially in the order they appear in the unit file. Optionally, if the absolute file name is prefixed with @, the second token will be passed as argv[0] to the executed process, followed by the further arguments specified. If the first token 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 ignored and considered success. If both - and @ are used they can appear in either order. Unless Type=forking is set, the process started via this command line will be considered the main process of the daemon. The command line accepts % specifiers as described in systemd.unit5. On top of that 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 replaced by the value of the environment variable including all whitespace it contains, resulting in 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 up at whitespace, resulting in no or more arguments. Note that the first argument (i.e. the program to execute) may not be a variable, and must be a literal and absolute path name. Note that this setting does not directly support shell command lines. If shell command lines are to be used they need to be passed explicitly to a shell implementation of some kind. Example: ExecStart=/bin/sh -c 'dmesg | tac' For services run by a user instance of systemd the special environment variable MANAGERPID is set to the PID of the systemd instance. ExecStartPre= ExecStartPost= Additional commands that are executed before or after the command in ExecStart=, respectively. Multiple command lines may be concatenated in a single directive, by separating them by semicolons (these semicolons must be passed as separate words). In that case, the commands are executed one after the other, serially. Alternatively, these directives may be specified more than once with the same effect. However, the latter syntax is not recommended for compatibility with parsers suitable for XDG .desktop files. Use of these settings is optional. Specifier and environment variable substitution is supported. ExecReload= Commands to execute to trigger a configuration reload in the service. This argument takes multiple command lines, following the same scheme as pointed out for ExecStartPre= 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 variables is set: if known $MAINPID is set to the main process of the daemon, and may be used for command lines like the following: /bin/kill -HUP $MAINPID. ExecStop= Commands to execute to stop the service started via ExecStart=. This argument takes multiple command lines, following the same scheme as pointed out for ExecStartPre= above. Use of this setting is optional. All processes remaining for a service after the commands configured in this option are run are terminated according to the KillMode= setting (see systemd.kill5). If this option is not specified the process is terminated right-away when service stop is requested. Specifier and environment variable substitution is supported (including $MAINPID, see above). ExecStopPost= Additional commands that are executed after the service was stopped using the commands configured in ExecStop=. This argument takes multiple command lines, following the same scheme as pointed out for ExecStartPre. Use of these settings is optional. Specifier and environment variable substitution is supported. 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 be shut down again. Takes a unit-less value in seconds, or a time span value such as "5min 20s". Pass 0 to disable the timeout logic. Defaults to 90s, except when Type=oneshot is used in which case the timeout is disabled by default. TimeoutStopSec= Configures the time to wait for stop. If a service is asked to stop but does not terminate in the specified time, it will be terminated forcibly via SIGTERM, and after another delay of this time with SIGKILL (See KillMode= in systemd.kill5). Takes a unit-less value in seconds, or a time span value such as "5min 20s". Pass 0 to disable the timeout logic. Defaults to 90s. TimeoutSec= A shorthand for configuring both TimeoutStartSec= and TimeoutStopSec= to the specified value. WatchdogSec= Configures the watchdog timeout for a service. This is activated when the start-up is completed. The service must call sd_notify3 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 failure state. By setting Restart= to on-failure 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. Restart= Configures whether the main service process shall be restarted when it exits. Takes one of no, on-success, on-failure, on-abort or always. If set to no (the default) the service will not be restarted when it exits. If set to on-success it will be restarted only when it exited cleanly, i.e. terminated with an exit code of 0. If set to on-failure it will be restarted only when it exited with an exit code not equaling 0, when terminated by a signal (including on core dump), when an operation (such as service reload) times out or when the configured watchdog timeout is triggered. If set to on-abort it will be restarted only if it exits due to reception of an uncaught signal (including on core dump). If set to always the service will be restarted regardless whether it exited cleanly or not, got terminated abnormally by a signal or hit a timeout. 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 code 0 and the signals SIGHUP, SIGINT, SIGTERM and SIGPIPE. Exit status definitions can either be numeric exit codes or termination signal names, and are separated by spaces. Example: "SuccessExitStatus=1 2 8 SIGKILL", ensures that exit codes 1, 2, 8 and the termination signal SIGKILL are considered clean service terminations. 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. Example: "RestartPreventExitStatus=1 6 SIGABRT", ensures that exit codes 1 and 6 and the termination signal SIGABRT will not result in automatic service restarting. PermissionsStartOnly= Takes a boolean argument. If true, the permission related execution options as configured with User= and similar options (see systemd.exec5 for more information) are only applied to the process started with ExecStart=, and not to the various other ExecStartPre=, ExecStartPost=, ExecReload=, ExecStop=, ExecStopPost= commands. If false, the setting is applied to all configured commands the same way. Defaults to false. RootDirectoryStartOnly= Takes a boolean argument. If true, the root directory as configured with the RootDirectory= option (see systemd.exec5 for more information) is only applied to the process started with ExecStart=, and not to the various other ExecStartPre=, ExecStartPost=, ExecReload=, ExecStop=, ExecStopPost= commands. If false, the setting is applied to all configured commands the same way. Defaults to false. NonBlocking= Set 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) 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.socket5. Defaults to false. NotifyAccess= Controls access to the service status notification socket, as accessible via the sd_notify3 call. Takes one of none (the default), main 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 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 WatchdogUsec= (see above). If those options are used but NotifyAccess= not configured it will be implicitly set to main. Sockets= Specifies the name of the socket units this service shall inherit the sockets from when the service is started. Normally it should not be necessary to use this setting as all sockets whose unit shares the same name as the service (ignoring the different suffix of course) are passed to the spawned process. Note that the same socket may be passed to multiple processes at the same time. Also note that a different service may be activated on incoming traffic than inherits the sockets. Or in other words: The Service= setting of .socket units doesn't have to match the inverse of the Sockets= setting of the .service it refers to. StartLimitInterval= StartLimitBurst= Configure service start rate limiting. By default services which are started more often than 5 times within 10s are not permitted to start any more times until the 10s interval ends. With these two options this rate limiting may be modified. Use StartLimitInterval= to configure the checking interval (defaults to 10s, set to 0 to disable any kind of rate limiting). Use StartLimitBurst= to configure how many starts per interval are allowed (defaults to 5). These configuration options are particularly useful in conjunction with Restart=, however apply to all kinds of starts (including manual), not just those triggered by the Restart= logic. Note that units which are configured for Restart= and which reach the start limit are not attempted to be restarted anymore, however they may still be restarted manually at a later point from which point on the restart logic is again activated. Note that systemctl reset-failed will cause the restart rate counter for a service to be flushed, which is useful if the administrator wants to manually start a service and the start limit interferes with that. StartLimitAction= Configure the action to take if the rate limit configured with StartLimitInterval= and StartLimitBurst= is hit. Takes one of none, reboot, reboot-force or reboot-immediate. If none is set, hitting the rate limit will trigger no action besides that the start will not be permitted. reboot causes a reboot following the normal shutdown procedure (i.e. equivalent to systemctl reboot), reboot-force causes an 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 reboot2 system call, which might result in data loss. Defaults to none. Check systemd.exec5 and systemd.kill5 for more settings. The following options are also available in the [Service] section, but exist purely for compatibility reasons and should not be used in newly written service files. SysVStartPriority= Set the SysV start priority to use to order this service in relation to SysV services lacking LSB headers. This option is only necessary to fix ordering in relation to legacy SysV services, that have no ordering information encoded in the script headers. As such it should only be used as temporary compatibility option, and not be used in new unit files. Almost always it is a better choice to add explicit ordering directives via After= or Before=, instead. For more details see systemd.unit5. If used, pass an integer value in the range 0-99. FsckPassNo= Set the fsck passno priority to use to order this service in relation to other file system checking services. This option is only necessary to fix ordering in relation to fsck jobs automatically created for all /etc/fstab entries with a value in the fs_passno column > 0. As such it should only be used as option for fsck services. Almost always it is a better choice to add explicit ordering directives via After= or Before=, instead. For more details see systemd.unit5. If used, pass an integer value in the same range as /etc/fstab's fs_passno column. See fstab5 for details. systemd1, systemctl8, systemd.unit5, systemd.exec5, systemd.kill5