SYSTEMD.SERVICE(5)



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.

       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
       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
   Implicit Dependencies
       The following dependencies are implicitly added:

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

       o   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:

       o   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.

       o   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
       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:

           o   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).

           o   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).

           o   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.

           o   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 continously. 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.

           o   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.

           o   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
           .

           o   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.

       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.

       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:

               /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, 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.
           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 exended
           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. 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 exended 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
           exended 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.

       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 exended 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 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 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 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) 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 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 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 with the SuccessExitStatus= setting

               SuccessExitStatus=TEMPFAIL 250 SIGUSR1

           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.

       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. 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 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
       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 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 to wrap a
       whole item (the opening quote may appear only at the beginning or after
       whitespace that is not quoted, and the closing quote must be followed
       by whitespace or the end of line), in which case everything until the
       next matching quote becomes part of the same argument. Quotes
       themselves are removed. C-style escapes are also supported. The table
       below contains the list of known escape patterns. Only escape patterns
       which match the syntax in the table are allowed; other patterns may be
       added in the future and unknown patterns will result in a warning. In
       particular, any backslashes should be doubled. Finally, a trailing
       backslash ("\") may be used to merge lines.

       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 determinted 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".

       Table 3. 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 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
       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
        1. Incompatibilities with SysV
           https://www.freedesktop.org/wiki/Software/systemd/Incompatibilities

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

systemd 245                                                 SYSTEMD.SERVICE(5)

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