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

NAME
       systemd.service - Service unit configuration

SYNOPSIS
       service.service

DESCRIPTION
       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.

       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[1] document.

OPTIONS
       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) and
       systemd.kill(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, forking, oneshot, dbus, notify or idle.

	   If set to simple (the default if neither Type= nor BusName=, but
	   ExecStart= are 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 are 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 with 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.
	   This is the implied default if neither Type= or ExecStart= are
	   specified.

	   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 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.

	   Behavior of notify is similar to simple; however, it is expected
	   that the daemon 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 not set, it will be
	   implicitly set to main. Note that currently Type=notify will not
	   work if used in combination with PrivateNetwork=yes.

	   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, although it will remove the file after
	   the service has shut down if it still exists.

       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.

       BusPolicy=
	   If specified, a custom kdbus[2] endpoint will be created and
	   installed as the default bus node for the service. Such a custom
	   endpoint can hold an own set of policy rules that are enforced on
	   top of the bus-wide ones. The custom endpoint is named after the
	   service it was created for, and its node will be bind-mounted over
	   the default bus node location, so the service can only access the
	   bus through its own endpoint. Note that custom bus endpoints
	   default to a 'deny all' policy. Hence, if at least one BusPolicy=
	   directive is given, you have to make sure to add explicit rules for
	   everything the service should be able to do.

	   The value of this directive is comprised of two parts; the bus
	   name, and a verb to specify to granted access, which is one of see,
	   talk, or own.  talk implies see, and own implies both talk and see.
	   If multiple access levels are specified for the same bus name, the
	   most powerful one takes effect.

	   Examples:

	       BusPolicy=org.freedesktop.systemd1 talk

	       BusPolicy=org.foo.bar see

	   This option is only available on kdbus enabled systems.

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

	   When Type is not oneshot, only one command may and must be given.
	   When Type=oneshot is used, zero or more commands may be specified.
	   This can 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 set.

	   For each of the specified commands, the first argument must be an
	   absolute path to an executable. Optionally, if this 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 absolute filename 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.

	   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.

	   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.

       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:

	       /bin/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.

       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, all
	   processes remaining for a service are terminated according to the
	   KillMode= setting (see systemd.kill(5)). If this option is not
	   specified, the process is terminated immediately 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. 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.

       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.
	   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
	   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)).

       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 timeout of equal
	   duration with SIGKILL (see KillMode= in systemd.kill(5)). 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
	   DefaultTimeoutStopSec= from the manager configuration file (see
	   systemd-system.conf(5)).

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

       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. 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 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 an exit code of 0, or one of the signals SIGHUP, SIGINT,
	   SIGTERM or SIGPIPE, and additionally, 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 aforementiond 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 1. Exit causes and the effect of the Restart= settings on
	   them
	   +--------------+----+--------+------------+------------+-------------+----------+-------------+
	   |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). Also, the services will
	   always be restarted if the exit code or signal is specified in
	   RestartForceExitStatus= (see below).

	   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 code 0 and the signals
	   SIGHUP, SIGINT, SIGTERM, and SIGPIPE. Exit status definitions can
	   either be numeric exit codes or termination signal names, separated
	   by spaces. For example:

	       SuccessExitStatus=1 2 8
		       SIGKILL

	   ensures that exit codes 1, 2, 8 and the termination signal SIGKILL
	   are considered clean service terminations.

	   Note that if a process has a signal handler installed and exits by
	   calling _exit(2) in response to a signal, the information about the
	   signal is lost. Programs should instead perform cleanup and kill
	   themselves with the same signal instead. See Proper handling of
	   SIGINT/SIGQUIT -- How to be a proper program[3].

	   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.

       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.

       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=.

       PermissionsStartOnly=
	   Takes a boolean argument. If true, the permission-related execution
	   options, as configured with User= and similar options (see
	   systemd.exec(5) for more information), are 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.

       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, and 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.socket(5). 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 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 WatchdogSec= (see above). If those options are used
	   but NotifyAccess= is not configured, it will be implicitly set to
	   main.

       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. If the empty string is assigned to this
	   option, the list of sockets is reset, and all prior uses of this
	   setting will have no effect.

       StartLimitInterval=, StartLimitBurst=
	   Configure service start rate limiting. By default, services which
	   are started more than 5 times within 10 seconds are not permitted
	   to start any more times until the 10 second interval ends. With
	   these two options, this rate limiting may be modified. Use
	   StartLimitInterval= to configure the checking interval (defaults to
	   DefaultStartLimitInterval= in manager configuration file, set to 0
	   to disable any kind of rate limiting). Use StartLimitBurst= to
	   configure how many starts per interval are allowed (defaults to
	   DefaultStartLimitBurst= in manager configuration file). These
	   configuration options are particularly useful in conjunction with
	   Restart=; however, they apply to all kinds of starts (including
	   manual), not just those triggered by the Restart= logic. Note that
	   units which are configured for Restart= and which reach the start
	   limit are not attempted to be restarted anymore; however, they may
	   still be restarted manually at a later point, from which point on,
	   the restart logic is again activated. Note that systemctl
	   reset-failed will cause the restart rate counter for a service to
	   be flushed, which is useful if the administrator wants to manually
	   start a 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, reboot-immediate, poweroff, poweroff-force or
	   poweroff-immediate. If none is set, hitting the rate limit will
	   trigger no action besides that the start will not be permitted.
	   reboot causes a reboot following the normal shutdown procedure
	   (i.e. equivalent to systemctl reboot).  reboot-force causes a
	   forced reboot which will terminate all processes forcibly but
	   should cause no dirty file systems on reboot (i.e. equivalent to
	   systemctl reboot -f) and reboot-immediate causes immediate
	   execution of the reboot(2) system call, which might result in data
	   loss. Similar, poweroff, poweroff-force, poweroff-immediate have
	   the effect of powering down the system with similar semantics.
	   Defaults to none.

       FailureAction=
	   Configure the action to take when the service enters a failed
	   state. Takes the same values as StartLimitAction= and executes the
	   same actions. Defaults to none.

       RebootArgument=
	   Configure the optional argument for the reboot(2) system call if
	   StartLimitAction= or FailureAction= is a reboot action. This works
	   just like the optional argument to systemctl reboot command.

       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 service
	   restart schemes where the state is serialized to /run and the file
	   descriptors passed to the service manager, to allow restarts
	   without losing state. Defaults to 0, i.e. no file descriptors may
	   be stored in the service manager by default. 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. 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 queued or being executed for it.

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

COMMAND LINES
       This section describes command line parsing and variable and specifier
       substitions 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 split on whitespace, with the first item being the
       command to execute, and the subsequent items being the arguments.
       Double quotes ("...") and single quotes ('...') may be used, in which
       case everything until the next matching quote becomes part of the same
       argument. C-style escapes are also supported, see table below. Quotes
       themselves are removed after parsing and escape sequences substituted.
       In addition, a trailing backslash ("\") may be used to merge lines.

       This syntax is intended to be very similar to shell syntax, but only
       the meta-characters and expansions described in the following
       paragraphs are understood. 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 must an absolute path name. It may contain
       spaces, but control characters are not allowed.

       The command line accepts "%" specifiers as described in
       systemd.unit(5). Note that the first argument of the command line (i.e.
       the program to execute) may not include specifiers.

       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 at
       whitespace resulting in zero or more arguments. For this type of
       expansion, quotes and respected when splitting into words, and
       afterwards removed.

       Example:

	   Environment="ONE=one" 'TWO=two two'
	   ExecStart=/bin/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 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=/bin/sh -c 'dmesg | tac'

       Example:

	   ExecStart=/bin/echo one ; /bin/echo "two two"

       This will execute /bin/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=/bin/echo / >/dev/null & \; \
	   /bin/ls

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

       Table 2. C escapes supported in command lines and environment variables
       +--------+-------------------------+
       |Literal | Actual value		  |
       +--------+-------------------------+
       |"\a"	| bell			  |
       +--------+-------------------------+
       |"\b"	| backspace		  |
       +--------+-------------------------+
       |"\f"	| form feed		  |
       +--------+-------------------------+
       |"\n"	| newline		  |
       +--------+-------------------------+
       |"\r"	| carriage return	  |
       +--------+-------------------------+
       |"\t"	| tab			  |
       +--------+-------------------------+
       |"\v"	| vertical tab		  |
       +--------+-------------------------+
       |"\\"	| backslash		  |
       +--------+-------------------------+
       |"\""	| double quotation mark	  |
       +--------+-------------------------+
       |"\'"	| single quotation mark	  |
       +--------+-------------------------+
       |"\s"	| space			  |
       +--------+-------------------------+
       |"\xxx"	| character number xx in  |
       |	| hexadecimal encoding	  |
       +--------+-------------------------+
       |"\nnn"	| character number nnn in |
       |	| octal encoding	  |
       +--------+-------------------------+

EXAMPLES
       Example 1. 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 2. 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 clenaup 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. They will be executed in order until either they
       are all successful or one of them fails.

       Example 3. 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 a 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 4. 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 5. 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, don't 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 6. 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 hasn't 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
       systemd(1), systemctl(1), systemd.unit(5), systemd.exec(5),
       systemd.resource-control(5), systemd.kill(5), systemd.directives(7)

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

	2. kdbus
	   https://code.google.com/p/d-bus/

	3. Proper handling of SIGINT/SIGQUIT -- How to be a proper program
	   http://www.cons.org/cracauer/sigint.html

systemd 219						    SYSTEMD.SERVICE(5)


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