SYSTEMD.SERVICE(5)systemd.serviceSYSTEMD.SERVICE(5)NAMEsystemd.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 value if neither Type= nor BusName=
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 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.
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.
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. For each of the specified commands, the first argument
must be an absolute and literal path to an executable.
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. 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.
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. Quotes themselves are removed
after parsing. 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 "|", and running
programs in the background using "&" and other elements of shell
syntax are not supported.
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 at whitespace, resulting in zero or more arguments.
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
section "Environment variables in spawned processes" in
systemd.exec(5) which are considered "static configuration" may
used (this includes e.g. $USER, but not $TERM).
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
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.
Note that this setting does not directly support shell command
lines. If shell command lines are to be used, they need to be
passed explicitly to a shell implementation of some kind. Example:
ExecStart=/bin/sh -c 'dmesg | tac'
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. Since 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".
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".
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.
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:
/bin/kill -HUP $MAINPID
ExecStop=
Commands to execute to stop the service started via ExecStart=.
This argument takes multiple command lines, following the same
scheme as 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 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 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
TimeoutStartSec= in manager configuration file, 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 TimeoutStartSec= in manager
configuration file.
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-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 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 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.
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. 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[2].
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= is 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 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, 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
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 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 ALSOsystemd(1), systemctl(8), 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. Proper handling of SIGINT/SIGQUIT — How to be a proper program
http://www.cons.org/cracauer/sigint.html
systemd 208SYSTEMD.SERVICE(5)
