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SYSTEMD.SERVICE(5) | systemd.service | SYSTEMD.SERVICE(5) |
NAME¶
systemd.service - Service unit configurationSYNOPSIS¶
service.serviceDESCRIPTION¶
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. 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 value if BusName= is not specified)
it is expected that the process configured with ExecStart= is the main
process of the service. In this mode, if the process offers functionality to
other processes on the system its communication channels should be installed
before the daemon is started up (e.g. sockets set up by systemd, via socket
activation), as systemd will immediately proceed starting follow-up units.
If set to forking it is expected that the process configured with
ExecStart= will call fork() as part of its start-up. The parent
process is expected to exit when start-up is complete and all communication
channels set up. The child continues to run as the main daemon process. This
is the behavior of traditional UNIX daemons. If this setting is used, it is
recommended to also use the PIDFile= option, so that systemd can
identify the main process of the daemon. systemd will proceed starting
follow-up units as soon as the parent process exits.
Behavior of oneshot is similar to simple, however it is expected
that the process has to exit before systemd starts follow-up units.
RemainAfterExit= is particularly useful for this type of service.
Behavior of dbus is similar to simple, however it is expected that
the daemon acquires a name on the D-Bus bus, as configured by BusName=.
systemd will proceed starting follow-up units after the D-Bus bus name has
been acquired. Service units with this option configured implicitly gain
dependencies on the dbus.socket unit. This type is the default if
BusName= is specified.
Behavior of notify is similar to simple, however it is expected
that the daemon sends a notification message via sd_notify(3) or an
equivalent call when it finished starting up. systemd will proceed starting
follow-up units after this notification message has been sent. If this option
is used NotifyAccess= (see below) should be set to open access to the
notification socket provided by systemd. If NotifyAccess= is not set,
it will be implicitly set to main.
Behavior of idle is very similar to simple, however actual
execution of the service binary is delayed until all jobs are dispatched. This
may be used to avoid interleaving of output of shell services with the status
output on the console.
RemainAfterExit=
Takes a boolean value that specifies whether
the service shall be considered active even when all its processes exited.
Defaults to no.
GuessMainPID=
Takes a boolean value that specifies whether
systemd should try to guess the main PID of a service if it cannot be
determined reliably. This option is ignored unless Type=forking is set
and PIDFile= is unset because for the other types or with an explicitly
configured PID file the main PID is always known. The guessing algorithm might
come to incorrect conclusions if a daemon consists of more than one process.
If the main PID cannot be determined failure detection and automatic
restarting of a service will not work reliably. Defaults to yes.
PIDFile=
Takes an absolute file name pointing to the
PID file of this daemon. Use of this option is recommended for services where
Type= is set to forking. systemd will read the PID of the main
process of the daemon after start-up of the service. systemd will not write to
the file configured here.
BusName=
Takes a D-Bus bus name, that this service is
reachable as. This option is mandatory for services where Type= is set
to dbus, but its use is otherwise recommended as well if the process
takes a name on the D-Bus bus.
ExecStart=
Commands with their arguments that are
executed when this service is started. The first argument must be an absolute
path name.
When Type is not oneshot, only one command may be given. When
Type=oneshot is used, more than one command may be specified. Multiple
command lines may be concatenated in a single directive, by separating them
with semicolons (these semicolons must be passed as separate words).
Alternatively, this directive may be specified more than once with the same
effect. However, the latter syntax is not recommended for compatibility with
parsers suitable for XDG .desktop files. Lone semicolons may be escaped as
'\;'. 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 more than one command is specified, the commands are invoked one by one
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.
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 up at whitespace, resulting in zero or more
arguments. Note that the first argument (i.e. the program to execute) may not
be a variable, since it must be a literal and absolute path name.
Optionally, if the absolute file name is prefixed with '@', the second token
will be passed as argv[0] to the executed process, followed by the further
arguments specified. If the absolute file name 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.
Note that this setting does not directly support shell command lines. If shell
command lines are to be used they need to be passed explicitly to a shell
implementation of some kind. Example:
For services run by a user instance of systemd the special environment variable
$MANAGERPID is set to the PID of the systemd instance.
ExecStartPre=, ExecStartPost=
ExecStart=/bin/sh -c 'dmesg | tac'
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.
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 variables is set: if known $MAINPID is
set to the main process of the daemon, and may be used for command lines like
the following:
ExecStop=
/bin/kill -HUP $MAINPID
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. All processes remaining for a service after the
commands configured in this option are run are terminated according to the
KillMode= setting (see systemd.kill(5)). If this option is not
specified the process is terminated right-away when service stop is requested.
Specifier and environment variable substitution is supported (including
$MAINPID, see above).
ExecStopPost=
Additional commands that are executed after
the service was stopped. This includes cases where the commands configured in
ExecStop= were used, where the service doesn't 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 be shut down again. Takes a
unit-less value in seconds, or a time span value such as "5min 20s".
Pass 0 to disable the timeout logic. Defaults to 90s, except when
Type=oneshot is used in which case the timeout is disabled by
default.
TimeoutStopSec=
Configures the time to wait for stop. If a
service is asked to stop but does not terminate in the specified time, it will
be terminated forcibly via SIGTERM, and after another delay of this time with
SIGKILL (See KillMode= in systemd.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 90s.
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 failure state. By
setting Restart= to on-failure or always the service will
be automatically restarted. The time configured here will be passed to the
executed service process in the WATCHDOG_USEC= environment variable.
This allows daemons to automatically enable the keep-alive pinging logic if
watchdog support is enabled for the service. If this option is used
NotifyAccess= (see below) should be set to open access to the
notification socket provided by systemd. If NotifyAccess= is not set,
it will be implicitly set to main. Defaults to 0, which disables this
feature.
Restart=
Configures whether the 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 also one of the
processes specified with ExecStartPre=, ExecStartPost=,
ExecStopPre=, 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-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 an nonzero exit code, is terminated by a
signal (including on core dump), when an operation (such as service reload)
times out, and when the configured 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 always the service will be restarted regardless whether it exited
cleanly or not, got terminated abnormally by a signal or hit a timeout.
In addition to the above settings, the service will not be restarted if the exit
code or signal is specified in RestartPreventExitStatus= (see
below).
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. Example:
"SuccessExitStatus=1 2 8 SIGKILL", ensures that exit codes 1, 2, 8
and the termination signal SIGKILL are considered clean service terminations.
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. 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, all prior assignments of this option will have no
effect.
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=, 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=, ExecStopPost= commands. If false, the setting is
applied to all configured commands the same way. Defaults to false.
NonBlocking=
Set O_NONBLOCK flag for all file descriptors
passed via socket-based activation. If true, all file descriptors >= 3
(i.e. all except STDIN/STDOUT/STDERR) will have the O_NONBLOCK flag set and
hence are in non-blocking mode. This option is only useful in conjunction with
a socket unit, as described in systemd.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= not configured it will be implicitly set to
main.
Sockets=
Specifies the name of the socket units this
service shall inherit the sockets from when the service is started. Normally
it should not be necessary to use this setting as all sockets whose unit
shares the same name as the service (ignoring the different suffix of course)
are passed to the spawned process.
Note that the same socket may be passed to multiple processes at the same time.
Also note that a different service may be activated on incoming traffic than
inherits the sockets. Or in other words: the Service= setting of
.socket units doesn't have to match the inverse of the Sockets= setting
of the .service it refers to.
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, all prior uses of this setting will have no effect.
StartLimitInterval=, StartLimitBurst=
Configure service start rate limiting. By
default services which are started more often than 5 times within 10s are not
permitted to start any more times until the 10s interval ends. With these two
options this rate limiting may be modified. Use StartLimitInterval= to
configure the checking interval (defaults to 10s, set to 0 to disable any kind
of rate limiting). Use StartLimitBurst= to configure how many starts
per interval are allowed (defaults to 5). These configuration options are
particularly useful in conjunction with Restart=, however apply to all
kinds of starts (including manual), not just those triggered by the
Restart= logic. Note that units which are configured for
Restart= and which reach the start limit are not attempted to be
restarted anymore, however they may still be restarted manually at a later
point from which point on the restart logic is again activated. Note that
systemctl reset-failed will cause the restart rate counter for a
service to be flushed, which is useful if the administrator wants to manually
start a service and the start limit interferes with that.
StartLimitAction=
Configure the action to take if the rate limit
configured with StartLimitInterval= and StartLimitBurst= is hit.
Takes one of none, reboot, reboot-force or
reboot-immediate. If none is set, hitting the rate limit will
trigger no action besides that the start will not be permitted. reboot
causes a reboot following the normal shutdown procedure (i.e. equivalent to
systemctl reboot), reboot-force causes an forced reboot which
will terminate all processes forcibly but should cause no dirty file systems
on reboot (i.e. equivalent to systemctl reboot -f) and
reboot-immediate causes immediate execution of the reboot(2)
system call, which might result in data loss. Defaults to none.
Check systemd.exec(5) and systemd.kill(5) for more settings.
COMPATIBILITY OPTIONS¶
The following options are also available in the [Service] section, but exist purely for compatibility reasons and should not be used in newly written service files. SysVStartPriority=Set the SysV start priority to use to order
this service in relation to SysV services lacking LSB headers. This option is
only necessary to fix ordering in relation to legacy SysV services, that have
no ordering information encoded in the script headers. As such it should only
be used as temporary compatibility option, and not be used in new unit files.
Almost always it is a better choice to add explicit ordering directives via
After= or Before=, instead. For more details see
systemd.unit(5). If used, pass an integer value in the range
0-99.
FsckPassNo=
Set the fsck passno priority to use to order
this service in relation to other file system checking services. This option
is only necessary to fix ordering in relation to fsck jobs automatically
created for all /etc/fstab entries with a value in the fs_passno column >
0. As such it should only be used as option for fsck services. Almost always
it is a better choice to add explicit ordering directives via After= or
Before=, instead. For more details see systemd.unit(5). If used,
pass an integer value in the same range as /etc/fstab's fs_passno column. See
fstab(5) for details.
SEE ALSO¶
NOTES¶
- 1.
- Incompatibilities with SysV
systemd 204 |