1SYSTEMD.SERVICE(5) systemd.service SYSTEMD.SERVICE(5)
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6 systemd.service - Service unit configuration
7
9 service.service
10
12 A unit configuration file whose name ends in ".service" encodes
13 information about a process controlled and supervised by systemd.
14 This man page lists the configuration options specific to this unit
16 type. See systemd.unit(5) for the common options of all unit
17 configuration files. The common configuration items are configured in
18 the generic "[Unit]" and "[Install]" sections. The service specific
19 configuration options are configured in the "[Service]" section.
20 Additional options are listed in systemd.exec(5), which define the
22 execution environment the commands are executed in, and in
23 systemd.kill(5), which define the way the processes of the service are
24 terminated, and in systemd.resource-control(5), which configure
25 resource control settings for the processes of the service.
26 If a service is requested under a certain name but no unit
28 configuration file is found, systemd looks for a SysV init script by
29 the same name (with the .service suffix removed) and dynamically
30 creates a service unit from that script. This is useful for
31 compatibility with SysV. Note that this compatibility is quite
32 comprehensive but not 100%. For details about the incompatibilities,
33 see the Incompatibilities with SysV[1] document.
34 The systemd-run(1) command allows creating .service and .scope units
36 dynamically and transiently from the command line.
37
39 It is possible for systemd services to take a single argument via the
40 "service@argument.service" syntax. Such services are called
41 "instantiated" services, while the unit definition without the argument
42 parameter is called a "template". An example could be a dhcpcd@.service
43 service template which takes a network interface as a parameter to form
44 an instantiated service. Within the service file, this parameter or
45 "instance name" can be accessed with %-specifiers. See systemd.unit(5)
46 for details.
47
49 Implicit Dependencies
50 The following dependencies are implicitly added:
51 · Services with Type=dbus set automatically acquire dependencies of
53 type Requires= and After= on dbus.socket.
54 · Socket activated services are automatically ordered after their
56 activating .socket units via an automatic After= dependency.
57 Services also pull in all .socket units listed in Sockets= via
58 automatic Wants= and After= dependencies.
59 Additional implicit dependencies may be added as result of execution
61 and resource control parameters as documented in systemd.exec(5) and
62 systemd.resource-control(5).
63 Default Dependencies
65 The following dependencies are added unless DefaultDependencies=no is
66 set:
67 · Service units will have dependencies of type Requires= and After=
69 on sysinit.target, a dependency of type After= on basic.target as
70 well as dependencies of type Conflicts= and Before= on
71 shutdown.target. These ensure that normal service units pull in
72 basic system initialization, and are terminated cleanly prior to
73 system shutdown. Only services involved with early boot or late
74 system shutdown should disable this option.
75 · Instanced service units (i.e. service units with an "@" in their
77 name) are assigned by default a per-template slice unit (see
78 systemd.slice(5)), named after the template unit, containing all
79 instances of the specific template. This slice is normally stopped
80 at shutdown, together with all template instances. If that is not
81 desired, set DefaultDependencies=no in the template unit, and
82 either define your own per-template slice unit file that also sets
83 DefaultDependencies=no, or set Slice=system.slice (or another
84 suitable slice) in the template unit. Also see systemd.resource-
85 control(5).
86
88 Service files must include a "[Service]" section, which carries
89 information about the service and the process it supervises. A number
90 of options that may be used in this section are shared with other unit
91 types. These options are documented in systemd.exec(5), systemd.kill(5)
92 and systemd.resource-control(5). The options specific to the
93 "[Service]" section of service units are the following:
94 Type=
96 Configures the process start-up type for this service unit. One of
97 simple, exec, forking, oneshot, dbus, notify or idle:
98 · If set to simple (the default if ExecStart= is specified but
100 neither Type= nor BusName= are), the service manager will
101 consider the unit started immediately after the main service
102 process has been forked off. It is expected that the process
103 configured with ExecStart= is the main process of the service.
104 In this mode, if the process offers functionality to other
105 processes on the system, its communication channels should be
106 installed before the service is started up (e.g. sockets set up
107 by systemd, via socket activation), as the service manager will
108 immediately proceed starting follow-up units, right after
109 creating the main service process, and before executing the
110 service's binary. Note that this means systemctl start command
111 lines for simple services will report success even if the
112 service's binary cannot be invoked successfully (for example
113 because the selected User= doesn't exist, or the service binary
114 is missing).
115 · The exec type is similar to simple, but the service manager
117 will consider the unit started immediately after the main
118 service binary has been executed. The service manager will
119 delay starting of follow-up units until that point. (Or in
120 other words: simple proceeds with further jobs right after
121 fork() returns, while exec will not proceed before both fork()
122 and execve() in the service process succeeded.) Note that this
123 means systemctl start command lines for exec services will
124 report failure when the service's binary cannot be invoked
125 successfully (for example because the selected User= doesn't
126 exist, or the service binary is missing).
127 · If set to forking, it is expected that the process configured
129 with ExecStart= will call fork() as part of its start-up. The
130 parent process is expected to exit when start-up is complete
131 and all communication channels are set up. The child continues
132 to run as the main service process, and the service manager
133 will consider the unit started when the parent process exits.
134 This is the behavior of traditional UNIX services. If this
135 setting is used, it is recommended to also use the PIDFile=
136 option, so that systemd can reliably identify the main process
137 of the service. systemd will proceed with starting follow-up
138 units as soon as the parent process exits.
139 · Behavior of oneshot is similar to simple; however, the service
141 manager will consider the unit up after the main process exits.
142 It will then start follow-up units. RemainAfterExit= is
143 particularly useful for this type of service. Type=oneshot is
144 the implied default if neither Type= nor ExecStart= are
145 specified. Note that if this option is used without
146 RemainAfterExit= the service will never enter "active" unit
147 state, but directly transition from "activating" to
148 "deactivating" or "dead" since no process is configured that
149 shall run continously. In particular this means that after a
150 service of this type ran (and which has RemainAfterExit= not
151 set) it will not show up as started afterwards, but as dead.
152 · Behavior of dbus is similar to simple; however, it is expected
154 that the service acquires a name on the D-Bus bus, as
155 configured by BusName=. systemd will proceed with starting
156 follow-up units after the D-Bus bus name has been acquired.
157 Service units with this option configured implicitly gain
158 dependencies on the dbus.socket unit. This type is the default
159 if BusName= is specified.
160 · Behavior of notify is similar to exec; however, it is expected
162 that the service sends a notification message via sd_notify(3)
163 or an equivalent call when it has finished starting up. systemd
164 will proceed with starting follow-up units after this
165 notification message has been sent. If this option is used,
166 NotifyAccess= (see below) should be set to open access to the
167 notification socket provided by systemd. If NotifyAccess= is
168 missing or set to none, it will be forcibly set to main
169 .
170 · Behavior of idle is very similar to simple; however, actual
174 execution of the service program is delayed until all active
175 jobs are dispatched. This may be used to avoid interleaving of
176 output of shell services with the status output on the console.
177 Note that this type is useful only to improve console output,
178 it is not useful as a general unit ordering tool, and the
179 effect of this service type is subject to a 5s timeout, after
180 which the service program is invoked anyway.
181 It is generally recommended to use Type=simple for long-running
183 services whenever possible, as it is the simplest and fastest
184 option. However, as this service type won't propagate service
185 start-up failures and doesn't allow ordering of other units against
186 completion of initialization of the service (which for example is
187 useful if clients need to connect to the service through some form
188 of IPC, and the IPC channel is only established by the service
189 itself — in contrast to doing this ahead of time through socket or
190 bus activation or similar), it might not be sufficient for many
191 cases. If so, notify or dbus (the latter only in case the service
192 provides a D-Bus interface) are the preferred options as they allow
193 service program code to precisely schedule when to consider the
194 service started up successfully and when to proceed with follow-up
195 units. The notify service type requires explicit support in the
196 service codebase (as sd_notify() or an equivalent API needs to be
197 invoked by the service at the appropriate time) — if it's not
198 supported, then forking is an alternative: it supports the
199 traditional UNIX service start-up protocol. Finally, exec might be
200 an option for cases where it is enough to ensure the service binary
201 is invoked, and where the service binary itself executes no or
202 little initialization on its own (and its initialization is
203 unlikely to fail). Note that using any type other than simple
204 possibly delays the boot process, as the service manager needs to
205 wait for service initialization to complete. It is hence
206 recommended not to needlessly use any types other than simple.
207 (Also note it is generally not recommended to use idle or oneshot
208 for long-running services.)
209 RemainAfterExit=
211 Takes a boolean value that specifies whether the service shall be
212 considered active even when all its processes exited. Defaults to
213 no.
214 GuessMainPID=
216 Takes a boolean value that specifies whether systemd should try to
217 guess the main PID of a service if it cannot be determined
218 reliably. This option is ignored unless Type=forking is set and
219 PIDFile= is unset because for the other types or with an explicitly
220 configured PID file, the main PID is always known. The guessing
221 algorithm might come to incorrect conclusions if a daemon consists
222 of more than one process. If the main PID cannot be determined,
223 failure detection and automatic restarting of a service will not
224 work reliably. Defaults to yes.
225 PIDFile=
227 Takes a path referring to the PID file of the service. Usage of
228 this option is recommended for services where Type= is set to
229 forking. The path specified typically points to a file below /run/.
230 If a relative path is specified it is hence prefixed with /run/.
231 The service manager will read the PID of the main process of the
232 service from this file after start-up of the service. The service
233 manager will not write to the file configured here, although it
234 will remove the file after the service has shut down if it still
235 exists. The PID file does not need to be owned by a privileged
236 user, but if it is owned by an unprivileged user additional safety
237 restrictions are enforced: the file may not be a symlink to a file
238 owned by a different user (neither directly nor indirectly), and
239 the PID file must refer to a process already belonging to the
240 service.
241 BusName=
243 Takes a D-Bus bus name that this service is reachable as. This
244 option is mandatory for services where Type= is set to dbus.
245 ExecStart=
247 Commands with their arguments that are executed when this service
248 is started. The value is split into zero or more command lines
249 according to the rules described below (see section "Command Lines"
250 below).
251 Unless Type= is oneshot, exactly one command must be given. When
253 Type=oneshot is used, zero or more commands may be specified.
254 Commands may be specified by providing multiple command lines in
255 the same directive, or alternatively, this directive may be
256 specified more than once with the same effect. If the empty string
257 is assigned to this option, the list of commands to start is reset,
258 prior assignments of this option will have no effect. If no
259 ExecStart= is specified, then the service must have
260 RemainAfterExit=yes and at least one ExecStop= line set. (Services
261 lacking both ExecStart= and ExecStop= are not valid.)
262 For each of the specified commands, the first argument must be
264 either an absolute path to an executable or a simple file name
265 without any slashes. Optionally, this filename may be prefixed with
266 a number of special characters:
267 Table 1. Special executable prefixes
269 ┌───────┬────────────────────────────┐
270 │Prefix │ Effect │
271 ├───────┼────────────────────────────┤
272 │"@" │ If the executable path is │
273 │ │ prefixed with "@", the │
274 │ │ second specified token │
275 │ │ will be passed as │
276 │ │ "argv[0]" to the executed │
277 │ │ process (instead of the │
278 │ │ actual filename), followed │
279 │ │ by the further arguments │
280 │ │ specified. │
281 ├───────┼────────────────────────────┤
282 │"-" │ If the executable path is │
283 │ │ prefixed with "-", an exit │
284 │ │ code of the command │
285 │ │ normally considered a │
286 │ │ failure (i.e. non-zero │
287 │ │ exit status or abnormal │
288 │ │ exit due to signal) is │
289 │ │ recorded, but has no │
290 │ │ further effect and is │
291 │ │ considered equivalent to │
292 │ │ success. │
293 ├───────┼────────────────────────────┤
294 │":" │ If the executable path is │
295 │ │ prefixed with ":", │
296 │ │ environment variable │
297 │ │ substitution (as described │
298 │ │ by the "Command Lines" │
299 │ │ section below) is not │
300 │ │ applied. │
301 ├───────┼────────────────────────────┤
302 │"+" │ If the executable path is │
303 │ │ prefixed with "+" then the │
304 │ │ process is executed with │
305 │ │ full privileges. In this │
306 │ │ mode privilege │
307 │ │ restrictions configured │
308 │ │ with User=, Group=, │
309 │ │ CapabilityBoundingSet= or │
310 │ │ the various file system │
311 │ │ namespacing options (such │
312 │ │ as PrivateDevices=, │
313 │ │ PrivateTmp=) are not │
314 │ │ applied to the invoked │
315 │ │ command line (but still │
316 │ │ affect any other │
317 │ │ ExecStart=, ExecStop=, ... │
318 │ │ lines). │
319 ├───────┼────────────────────────────┤
320 │"!" │ Similar to the "+" │
321 │ │ character discussed above │
322 │ │ this permits invoking │
323 │ │ command lines with │
324 │ │ elevated privileges. │
325 │ │ However, unlike "+" the │
326 │ │ "!" character exclusively │
327 │ │ alters the effect of │
328 │ │ User=, Group= and │
329 │ │ SupplementaryGroups=, i.e. │
330 │ │ only the stanzas that │
331 │ │ affect user and group │
332 │ │ credentials. Note that │
333 │ │ this setting may be │
334 │ │ combined with │
335 │ │ DynamicUser=, in which │
336 │ │ case a dynamic user/group │
337 │ │ pair is allocated before │
338 │ │ the command is invoked, │
339 │ │ but credential changing is │
340 │ │ left to the executed │
341 │ │ process itself. │
342 ├───────┼────────────────────────────┤
343 │"!!" │ This prefix is very │
344 │ │ similar to "!", however it │
345 │ │ only has an effect on │
346 │ │ systems lacking support │
347 │ │ for ambient process │
348 │ │ capabilities, i.e. without │
349 │ │ support for │
350 │ │ AmbientCapabilities=. It's │
351 │ │ intended to be used for │
352 │ │ unit files that take │
353 │ │ benefit of ambient │
354 │ │ capabilities to run │
355 │ │ processes with minimal │
356 │ │ privileges wherever │
357 │ │ possible while remaining │
358 │ │ compatible with systems │
359 │ │ that lack ambient │
360 │ │ capabilities support. Note │
361 │ │ that when "!!" is used, │
362 │ │ and a system lacking │
363 │ │ ambient capability support │
364 │ │ is detected any configured │
365 │ │ SystemCallFilter= and │
366 │ │ CapabilityBoundingSet= │
367 │ │ stanzas are implicitly │
368 │ │ modified, in order to │
369 │ │ permit spawned processes │
370 │ │ to drop credentials and │
371 │ │ capabilities themselves, │
372 │ │ even if this is configured │
373 │ │ to not be allowed. │
374 │ │ Moreover, if this prefix │
375 │ │ is used and a system │
376 │ │ lacking ambient capability │
377 │ │ support is detected │
378 │ │ AmbientCapabilities= will │
379 │ │ be skipped and not be │
380 │ │ applied. On systems │
381 │ │ supporting ambient │
382 │ │ capabilities, "!!" has no │
383 │ │ effect and is redundant. │
384 └───────┴────────────────────────────┘
385 "@", "-", ":", and one of "+"/"!"/"!!" may be used together and
386 they can appear in any order. However, only one of "+", "!", "!!"
387 may be used at a time. Note that these prefixes are also supported
388 for the other command line settings, i.e. ExecStartPre=,
389 ExecStartPost=, ExecReload=, ExecStop= and ExecStopPost=.
390 If more than one command is specified, the commands are invoked
392 sequentially in the order they appear in the unit file. If one of
393 the commands fails (and is not prefixed with "-"), other lines are
394 not executed, and the unit is considered failed.
395 Unless Type=forking is set, the process started via this command
397 line will be considered the main process of the daemon.
398 ExecStartPre=, ExecStartPost=
400 Additional commands that are executed before or after the command
401 in ExecStart=, respectively. Syntax is the same as for ExecStart=,
402 except that multiple command lines are allowed and the commands are
403 executed one after the other, serially.
404 If any of those commands (not prefixed with "-") fail, the rest are
406 not executed and the unit is considered failed.
407 ExecStart= commands are only run after all ExecStartPre= commands
409 that were not prefixed with a "-" exit successfully.
410 ExecStartPost= commands are only run after the commands specified
412 in ExecStart= have been invoked successfully, as determined by
413 Type= (i.e. the process has been started for Type=simple or
414 Type=idle, the last ExecStart= process exited successfully for
415 Type=oneshot, the initial process exited successfully for
416 Type=forking, "READY=1" is sent for Type=notify, or the BusName=
417 has been taken for Type=dbus).
418 Note that ExecStartPre= may not be used to start long-running
420 processes. All processes forked off by processes invoked via
421 ExecStartPre= will be killed before the next service process is
422 run.
423 Note that if any of the commands specified in ExecStartPre=,
425 ExecStart=, or ExecStartPost= fail (and are not prefixed with "-",
426 see above) or time out before the service is fully up, execution
427 continues with commands specified in ExecStopPost=, the commands in
428 ExecStop= are skipped.
429 ExecCondition=
431 Optional commands that are executed before the command(s) in
432 ExecStartPre=. Syntax is the same as for ExecStart=, except that
433 multiple command lines are allowed and the commands are executed
434 one after the other, serially.
435 The behavior is like an ExecStartPre= and condition check hybrid:
437 when an ExecCondition= command exits with exit code 1 through 254
438 (inclusive), the remaining commands are skipped and the unit is not
439 marked as failed. However, if an ExecCondition= command exits with
440 255 or abnormally (e.g. timeout, killed by a signal, etc.), the
441 unit will be considered failed (and remaining commands will be
442 skipped). Exit code of 0 or those matching SuccessExitStatus= will
443 continue execution to the next command(s).
444 The same recommendations about not running long-running processes
446 in ExecStartPre= also applies to ExecCondition=. ExecCondition=
447 will also run the commands in ExecStopPost=, as part of stopping
448 the service, in the case of any non-zero or abnormal exits, like
449 the ones described above.
450 ExecReload=
452 Commands to execute to trigger a configuration reload in the
453 service. This argument takes multiple command lines, following the
454 same scheme as described for ExecStart= above. Use of this setting
455 is optional. Specifier and environment variable substitution is
456 supported here following the same scheme as for ExecStart=.
457 One additional, special environment variable is set: if known,
459 $MAINPID is set to the main process of the daemon, and may be used
460 for command lines like the following:
461 /bin/kill -HUP $MAINPID
463 Note however that reloading a daemon by sending a signal (as with
465 the example line above) is usually not a good choice, because this
466 is an asynchronous operation and hence not suitable to order
467 reloads of multiple services against each other. It is strongly
468 recommended to set ExecReload= to a command that not only triggers
469 a configuration reload of the daemon, but also synchronously waits
470 for it to complete.
471 ExecStop=
473 Commands to execute to stop the service started via ExecStart=.
474 This argument takes multiple command lines, following the same
475 scheme as described for ExecStart= above. Use of this setting is
476 optional. After the commands configured in this option are run, it
477 is implied that the service is stopped, and any processes remaining
478 for it are terminated according to the KillMode= setting (see
479 systemd.kill(5)). If this option is not specified, the process is
480 terminated by sending the signal specified in KillSignal= or
481 RestartKillSignal= when service stop is requested. Specifier and
482 environment variable substitution is supported (including $MAINPID,
483 see above).
484 Note that it is usually not sufficient to specify a command for
486 this setting that only asks the service to terminate (for example,
487 by sending some form of termination signal to it), but does not
488 wait for it to do so. Since the remaining processes of the services
489 are killed according to KillMode= and KillSignal= or
490 RestartKillSignal= as described above immediately after the command
491 exited, this may not result in a clean stop. The specified command
492 should hence be a synchronous operation, not an asynchronous one.
493 Note that the commands specified in ExecStop= are only executed
495 when the service started successfully first. They are not invoked
496 if the service was never started at all, or in case its start-up
497 failed, for example because any of the commands specified in
498 ExecStart=, ExecStartPre= or ExecStartPost= failed (and weren't
499 prefixed with "-", see above) or timed out. Use ExecStopPost= to
500 invoke commands when a service failed to start up correctly and is
501 shut down again. Also note that the stop operation is always
502 performed if the service started successfully, even if the
503 processes in the service terminated on their own or were killed.
504 The stop commands must be prepared to deal with that case.
505 $MAINPID will be unset if systemd knows that the main process
506 exited by the time the stop commands are called.
507 Service restart requests are implemented as stop operations
509 followed by start operations. This means that ExecStop= and
510 ExecStopPost= are executed during a service restart operation.
511 It is recommended to use this setting for commands that communicate
513 with the service requesting clean termination. For post-mortem
514 clean-up steps use ExecStopPost= instead.
515 ExecStopPost=
517 Additional commands that are executed after the service is stopped.
518 This includes cases where the commands configured in ExecStop= were
519 used, where the service does not have any ExecStop= defined, or
520 where the service exited unexpectedly. This argument takes multiple
521 command lines, following the same scheme as described for
522 ExecStart=. Use of these settings is optional. Specifier and
523 environment variable substitution is supported. Note that – unlike
524 ExecStop= – commands specified with this setting are invoked when a
525 service failed to start up correctly and is shut down again.
526 It is recommended to use this setting for clean-up operations that
528 shall be executed even when the service failed to start up
529 correctly. Commands configured with this setting need to be able to
530 operate even if the service failed starting up half-way and left
531 incompletely initialized data around. As the service's processes
532 have been terminated already when the commands specified with this
533 setting are executed they should not attempt to communicate with
534 them.
535 Note that all commands that are configured with this setting are
537 invoked with the result code of the service, as well as the main
538 process' exit code and status, set in the $SERVICE_RESULT,
539 $EXIT_CODE and $EXIT_STATUS environment variables, see
540 systemd.exec(5) for details.
541 RestartSec=
543 Configures the time to sleep before restarting a service (as
544 configured with Restart=). Takes a unit-less value in seconds, or a
545 time span value such as "5min 20s". Defaults to 100ms.
546 TimeoutStartSec=
548 Configures the time to wait for start-up. If a daemon service does
549 not signal start-up completion within the configured time, the
550 service will be considered failed and will be shut down again.
551 Takes a unit-less value in seconds, or a time span value such as
552 "5min 20s". Pass "infinity" to disable the timeout logic. Defaults
553 to DefaultTimeoutStartSec= from the manager configuration file,
554 except when Type=oneshot is used, in which case the timeout is
555 disabled by default (see systemd-system.conf(5)).
556 If a service of Type=notify sends "EXTEND_TIMEOUT_USEC=...", this
558 may cause the start time to be extended beyond TimeoutStartSec=.
559 The first receipt of this message must occur before
560 TimeoutStartSec= is exceeded, and once the start time has exended
561 beyond TimeoutStartSec=, the service manager will allow the service
562 to continue to start, provided the service repeats
563 "EXTEND_TIMEOUT_USEC=..." within the interval specified until the
564 service startup status is finished by "READY=1". (see
565 sd_notify(3)).
566 TimeoutStopSec=
568 This option serves two purposes. First, it configures the time to
569 wait for each ExecStop= command. If any of them times out,
570 subsequent ExecStop= commands are skipped and the service will be
571 terminated by SIGTERM. If no ExecStop= commands are specified, the
572 service gets the SIGTERM immediately. Second, it configures the
573 time to wait for the service itself to stop. If it doesn't
574 terminate in the specified time, it will be forcibly terminated by
575 SIGKILL (see KillMode= in systemd.kill(5)). Takes a unit-less value
576 in seconds, or a time span value such as "5min 20s". Pass
577 "infinity" to disable the timeout logic. Defaults to
578 DefaultTimeoutStopSec= from the manager configuration file (see
579 systemd-system.conf(5)).
580 If a service of Type=notify sends "EXTEND_TIMEOUT_USEC=...", this
582 may cause the stop time to be extended beyond TimeoutStopSec=. The
583 first receipt of this message must occur before TimeoutStopSec= is
584 exceeded, and once the stop time has exended beyond
585 TimeoutStopSec=, the service manager will allow the service to
586 continue to stop, provided the service repeats
587 "EXTEND_TIMEOUT_USEC=..." within the interval specified, or
588 terminates itself (see sd_notify(3)).
589 TimeoutAbortSec=
591 This option configures the time to wait for the service to
592 terminate when it was aborted due to a watchdog timeout (see
593 WatchdogSec=). If the service has a short TimeoutStopSec= this
594 option can be used to give the system more time to write a core
595 dump of the service. Upon expiration the service will be forcibly
596 terminated by SIGKILL (see KillMode= in systemd.kill(5)). The core
597 file will be truncated in this case. Use TimeoutAbortSec= to set a
598 sensible timeout for the core dumping per service that is large
599 enough to write all expected data while also being short enough to
600 handle the service failure in due time.
601 Takes a unit-less value in seconds, or a time span value such as
603 "5min 20s". Pass an empty value to skip the dedicated watchdog
604 abort timeout handling and fall back TimeoutStopSec=. Pass
605 "infinity" to disable the timeout logic. Defaults to
606 DefaultTimeoutAbortSec= from the manager configuration file (see
607 systemd-system.conf(5)).
608 If a service of Type=notify handles SIGABRT itself (instead of
610 relying on the kernel to write a core dump) it can send
611 "EXTEND_TIMEOUT_USEC=..." to extended the abort time beyond
612 TimeoutAbortSec=. The first receipt of this message must occur
613 before TimeoutAbortSec= is exceeded, and once the abort time has
614 exended beyond TimeoutAbortSec=, the service manager will allow the
615 service to continue to abort, provided the service repeats
616 "EXTEND_TIMEOUT_USEC=..." within the interval specified, or
617 terminates itself (see sd_notify(3)).
618 TimeoutSec=
620 A shorthand for configuring both TimeoutStartSec= and
621 TimeoutStopSec= to the specified value.
622 RuntimeMaxSec=
624 Configures a maximum time for the service to run. If this is used
625 and the service has been active for longer than the specified time
626 it is terminated and put into a failure state. Note that this
627 setting does not have any effect on Type=oneshot services, as they
628 terminate immediately after activation completed. Pass "infinity"
629 (the default) to configure no runtime limit.
630 If a service of Type=notify sends "EXTEND_TIMEOUT_USEC=...", this
632 may cause the runtime to be extended beyond RuntimeMaxSec=. The
633 first receipt of this message must occur before RuntimeMaxSec= is
634 exceeded, and once the runtime has exended beyond RuntimeMaxSec=,
635 the service manager will allow the service to continue to run,
636 provided the service repeats "EXTEND_TIMEOUT_USEC=..." within the
637 interval specified until the service shutdown is achieved by
638 "STOPPING=1" (or termination). (see sd_notify(3)).
639 WatchdogSec=
641 Configures the watchdog timeout for a service. The watchdog is
642 activated when the start-up is completed. The service must call
643 sd_notify(3) regularly with "WATCHDOG=1" (i.e. the "keep-alive
644 ping"). If the time between two such calls is larger than the
645 configured time, then the service is placed in a failed state and
646 it will be terminated with SIGABRT (or the signal specified by
647 WatchdogSignal=). By setting Restart= to on-failure, on-watchdog,
648 on-abnormal or always, the service will be automatically restarted.
649 The time configured here will be passed to the executed service
650 process in the WATCHDOG_USEC= environment variable. This allows
651 daemons to automatically enable the keep-alive pinging logic if
652 watchdog support is enabled for the service. If this option is
653 used, NotifyAccess= (see below) should be set to open access to the
654 notification socket provided by systemd. If NotifyAccess= is not
655 set, it will be implicitly set to main. Defaults to 0, which
656 disables this feature. The service can check whether the service
657 manager expects watchdog keep-alive notifications. See
658 sd_watchdog_enabled(3) for details. sd_event_set_watchdog(3) may
659 be used to enable automatic watchdog notification support.
660 Restart=
662 Configures whether the service shall be restarted when the service
663 process exits, is killed, or a timeout is reached. The service
664 process may be the main service process, but it may also be one of
665 the processes specified with ExecStartPre=, ExecStartPost=,
666 ExecStop=, ExecStopPost=, or ExecReload=. When the death of the
667 process is a result of systemd operation (e.g. service stop or
668 restart), the service will not be restarted. Timeouts include
669 missing the watchdog "keep-alive ping" deadline and a service
670 start, reload, and stop operation timeouts.
671 Takes one of no, on-success, on-failure, on-abnormal, on-watchdog,
673 on-abort, or always. If set to no (the default), the service will
674 not be restarted. If set to on-success, it will be restarted only
675 when the service process exits cleanly. In this context, a clean
676 exit means an exit code of 0, or one of the signals SIGHUP, SIGINT,
677 SIGTERM or SIGPIPE, and additionally, exit statuses and signals
678 specified in SuccessExitStatus=. If set to on-failure, the service
679 will be restarted when the process exits with a non-zero exit code,
680 is terminated by a signal (including on core dump, but excluding
681 the aforementioned four signals), when an operation (such as
682 service reload) times out, and when the configured watchdog timeout
683 is triggered. If set to on-abnormal, the service will be restarted
684 when the process is terminated by a signal (including on core dump,
685 excluding the aforementioned four signals), when an operation times
686 out, or when the watchdog timeout is triggered. If set to on-abort,
687 the service will be restarted only if the service process exits due
688 to an uncaught signal not specified as a clean exit status. If set
689 to on-watchdog, the service will be restarted only if the watchdog
690 timeout for the service expires. If set to always, the service will
691 be restarted regardless of whether it exited cleanly or not, got
692 terminated abnormally by a signal, or hit a timeout.
693 Table 2. Exit causes and the effect of the Restart= settings on
695 them
696 ┌──────────────┬────┬────────┬────────────┬────────────┬─────────────┬──────────┬─────────────┐
697 │Restart │ no │ always │ on-success │ on-failure │ on-abnormal │ on-abort │ on-watchdog │
698 │settings/Exit │ │ │ │ │ │ │ │
699 │causes │ │ │ │ │ │ │ │
700 ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
701 │Clean exit │ │ X │ X │ │ │ │ │
702 │code or │ │ │ │ │ │ │ │
703 │signal │ │ │ │ │ │ │ │
704 ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
705 │Unclean exit │ │ X │ │ X │ │ │ │
706 │code │ │ │ │ │ │ │ │
707 ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
708 │Unclean │ │ X │ │ X │ X │ X │ │
709 │signal │ │ │ │ │ │ │ │
710 ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
711 │Timeout │ │ X │ │ X │ X │ │ │
712 ├──────────────┼────┼────────┼────────────┼────────────┼─────────────┼──────────┼─────────────┤
713 │Watchdog │ │ X │ │ X │ X │ │ X │
714 └──────────────┴────┴────────┴────────────┴────────────┴─────────────┴──────────┴─────────────┘
715 As exceptions to the setting above, the service will not be
716 restarted if the exit code or signal is specified in
717 RestartPreventExitStatus= (see below) or the service is stopped
718 with systemctl stop or an equivalent operation. Also, the services
719 will always be restarted if the exit code or signal is specified in
720 RestartForceExitStatus= (see below).
721 Note that service restart is subject to unit start rate limiting
723 configured with StartLimitIntervalSec= and StartLimitBurst=, see
724 systemd.unit(5) for details. A restarted service enters the failed
725 state only after the start limits are reached.
726 Setting this to on-failure is the recommended choice for
728 long-running services, in order to increase reliability by
729 attempting automatic recovery from errors. For services that shall
730 be able to terminate on their own choice (and avoid immediate
731 restarting), on-abnormal is an alternative choice.
732 SuccessExitStatus=
734 Takes a list of exit status definitions that, when returned by the
735 main service process, will be considered successful termination, in
736 addition to the normal successful exit code 0 and the signals
737 SIGHUP, SIGINT, SIGTERM, and SIGPIPE. Exit status definitions can
738 be numeric exit codes, termination code names, or termination
739 signal names, separated by spaces. See the Process Exit Codes
740 section in systemd.exec(5) for a list of termination codes names
741 (for this setting only the part without the "EXIT_" or "EX_" prefix
742 should be used). See signal(7) for a list of signal names.
743 This option may appear more than once, in which case the list of
745 successful exit statuses is merged. If the empty string is assigned
746 to this option, the list is reset, all prior assignments of this
747 option will have no effect.
748 Example 1. A service with with the SuccessExitStatus= setting
750 SuccessExitStatus=TEMPFAIL 250 SIGUSR1
752 Exit codes 75 (TEMPFAIL), 250, and the termination signal SIGKILL
754 are considered clean service terminations.
755 Note: systemd-analyze exit-codes may be used to list exit codes and
757 translate between numerical code values and names.
758 RestartPreventExitStatus=
760 Takes a list of exit status definitions that, when returned by the
761 main service process, will prevent automatic service restarts,
762 regardless of the restart setting configured with Restart=. Exit
763 status definitions can either be numeric exit codes or termination
764 signal names, and are separated by spaces. Defaults to the empty
765 list, so that, by default, no exit status is excluded from the
766 configured restart logic. For example:
767 RestartPreventExitStatus=1 6 SIGABRT
769 ensures that exit codes 1 and 6 and the termination signal SIGABRT
771 will not result in automatic service restarting. This option may
772 appear more than once, in which case the list of restart-preventing
773 statuses is merged. If the empty string is assigned to this option,
774 the list is reset and all prior assignments of this option will
775 have no effect.
776 Note that this setting has no effect on processes configured via
778 ExecStartPre=, ExecStartPost=, ExecStop=, ExecStopPost= or
779 ExecReload=, but only on the main service process, i.e. either the
780 one invoked by ExecStart= or (depending on Type=, PIDFile=, ...)
781 the otherwise configured main process.
782 RestartForceExitStatus=
784 Takes a list of exit status definitions that, when returned by the
785 main service process, will force automatic service restarts,
786 regardless of the restart setting configured with Restart=. The
787 argument format is similar to RestartPreventExitStatus=.
788 RootDirectoryStartOnly=
790 Takes a boolean argument. If true, the root directory, as
791 configured with the RootDirectory= option (see systemd.exec(5) for
792 more information), is only applied to the process started with
793 ExecStart=, and not to the various other ExecStartPre=,
794 ExecStartPost=, ExecReload=, ExecStop=, and ExecStopPost= commands.
795 If false, the setting is applied to all configured commands the
796 same way. Defaults to false.
797 NonBlocking=
799 Set the O_NONBLOCK flag for all file descriptors passed via
800 socket-based activation. If true, all file descriptors >= 3 (i.e.
801 all except stdin, stdout, stderr), excluding those passed in via
802 the file descriptor storage logic (see FileDescriptorStoreMax= for
803 details), will have the O_NONBLOCK flag set and hence are in
804 non-blocking mode. This option is only useful in conjunction with a
805 socket unit, as described in systemd.socket(5) and has no effect on
806 file descriptors which were previously saved in the file-descriptor
807 store for example. Defaults to false.
808 NotifyAccess=
810 Controls access to the service status notification socket, as
811 accessible via the sd_notify(3) call. Takes one of none (the
812 default), main, exec or all. If none, no daemon status updates are
813 accepted from the service processes, all status update messages are
814 ignored. If main, only service updates sent from the main process
815 of the service are accepted. If exec, only service updates sent
816 from any of the main or control processes originating from one of
817 the Exec*= commands are accepted. If all, all services updates from
818 all members of the service's control group are accepted. This
819 option should be set to open access to the notification socket when
820 using Type=notify or WatchdogSec= (see above). If those options are
821 used but NotifyAccess= is not configured, it will be implicitly set
822 to main.
823 Note that sd_notify() notifications may be attributed to units
825 correctly only if either the sending process is still around at the
826 time PID 1 processes the message, or if the sending process is
827 explicitly runtime-tracked by the service manager. The latter is
828 the case if the service manager originally forked off the process,
829 i.e. on all processes that match main or exec. Conversely, if an
830 auxiliary process of the unit sends an sd_notify() message and
831 immediately exits, the service manager might not be able to
832 properly attribute the message to the unit, and thus will ignore
833 it, even if NotifyAccess=all is set for it.
834 Sockets=
836 Specifies the name of the socket units this service shall inherit
837 socket file descriptors from when the service is started. Normally,
838 it should not be necessary to use this setting, as all socket file
839 descriptors whose unit shares the same name as the service (subject
840 to the different unit name suffix of course) are passed to the
841 spawned process.
842 Note that the same socket file descriptors may be passed to
844 multiple processes simultaneously. Also note that a different
845 service may be activated on incoming socket traffic than the one
846 which is ultimately configured to inherit the socket file
847 descriptors. Or, in other words: the Service= setting of .socket
848 units does not have to match the inverse of the Sockets= setting of
849 the .service it refers to.
850 This option may appear more than once, in which case the list of
852 socket units is merged. Note that once set, clearing the list of
853 sockets again (for example, by assigning the empty string to this
854 option) is not supported.
855 FileDescriptorStoreMax=
857 Configure how many file descriptors may be stored in the service
858 manager for the service using sd_pid_notify_with_fds(3)'s
859 "FDSTORE=1" messages. This is useful for implementing services that
860 can restart after an explicit request or a crash without losing
861 state. Any open sockets and other file descriptors which should not
862 be closed during the restart may be stored this way. Application
863 state can either be serialized to a file in /run, or better, stored
864 in a memfd_create(2) memory file descriptor. Defaults to 0, i.e. no
865 file descriptors may be stored in the service manager. All file
866 descriptors passed to the service manager from a specific service
867 are passed back to the service's main process on the next service
868 restart. Any file descriptors passed to the service manager are
869 automatically closed when POLLHUP or POLLERR is seen on them, or
870 when the service is fully stopped and no job is queued or being
871 executed for it. If this option is used, NotifyAccess= (see above)
872 should be set to open access to the notification socket provided by
873 systemd. If NotifyAccess= is not set, it will be implicitly set to
874 main.
875 USBFunctionDescriptors=
877 Configure the location of a file containing USB FunctionFS[2]
878 descriptors, for implementation of USB gadget functions. This is
879 used only in conjunction with a socket unit with ListenUSBFunction=
880 configured. The contents of this file are written to the ep0 file
881 after it is opened.
882 USBFunctionStrings=
884 Configure the location of a file containing USB FunctionFS strings.
885 Behavior is similar to USBFunctionDescriptors= above.
886 OOMPolicy=
888 Configure the Out-Of-Memory (OOM) killer policy. On Linux, when
889 memory becomes scarce the kernel might decide to kill a running
890 process in order to free up memory and reduce memory pressure. This
891 setting takes one of continue, stop or kill. If set to continue and
892 a process of the service is killed by the kernel's OOM killer this
893 is logged but the service continues running. If set to stop the
894 event is logged but the service is terminated cleanly by the
895 service manager. If set to kill and one of the service's processes
896 is killed by the OOM killer the kernel is instructed to kill all
897 remaining processes of the service, too. Defaults to the setting
898 DefaultOOMPolicy= in system.conf(5) is set to, except for services
899 where Delegate= is turned on, where it defaults to continue.
900 Use the OOMScoreAdjust= setting to configure whether processes of
902 the unit shall be considered preferred or less preferred candidates
903 for process termination by the Linux OOM killer logic. See
904 systemd.exec(5) for details.
905 Check systemd.exec(5) and systemd.kill(5) for more settings.
907
909 This section describes command line parsing and variable and specifier
910 substitutions for ExecStart=, ExecStartPre=, ExecStartPost=,
911 ExecReload=, ExecStop=, and ExecStopPost= options.
912 Multiple command lines may be concatenated in a single directive by
914 separating them with semicolons (these semicolons must be passed as
915 separate words). Lone semicolons may be escaped as "\;".
916 Each command line is split on whitespace, with the first item being the
918 command to execute, and the subsequent items being the arguments.
919 Double quotes ("...") and single quotes ('...') may be used to wrap a
920 whole item (the opening quote may appear only at the beginning or after
921 whitespace that is not quoted, and the closing quote must be followed
922 by whitespace or the end of line), in which case everything until the
923 next matching quote becomes part of the same argument. Quotes
924 themselves are removed. C-style escapes are also supported. The table
925 below contains the list of known escape patterns. Only escape patterns
926 which match the syntax in the table are allowed; other patterns may be
927 added in the future and unknown patterns will result in a warning. In
928 particular, any backslashes should be doubled. Finally, a trailing
929 backslash ("\") may be used to merge lines.
930 This syntax is inspired by shell syntax, but only the meta-characters
932 and expansions described in the following paragraphs are understood,
933 and the expansion of variables is different. Specifically, redirection
934 using "<", "<<", ">", and ">>", pipes using "|", running programs in
935 the background using "&", and other elements of shell syntax are not
936 supported.
937 The command to execute may contain spaces, but control characters are
939 not allowed.
940 The command line accepts "%" specifiers as described in
942 systemd.unit(5).
943 Basic environment variable substitution is supported. Use "${FOO}" as
945 part of a word, or as a word of its own, on the command line, in which
946 case it will be replaced by the value of the environment variable
947 including all whitespace it contains, resulting in a single argument.
948 Use "$FOO" as a separate word on the command line, in which case it
949 will be replaced by the value of the environment variable split at
950 whitespace, resulting in zero or more arguments. For this type of
951 expansion, quotes are respected when splitting into words, and
952 afterwards removed.
953 If the command is not a full (absolute) path, it will be resolved to a
955 full path using a fixed search path determinted at compilation time.
956 Searched directories include /usr/local/bin/, /usr/bin/, /bin/ on
957 systems using split /usr/bin/ and /bin/ directories, and their sbin/
958 counterparts on systems using split bin/ and sbin/. It is thus safe to
959 use just the executable name in case of executables located in any of
960 the "standard" directories, and an absolute path must be used in other
961 cases. Using an absolute path is recommended to avoid ambiguity. Hint:
962 this search path may be queried using systemd-path
963 search-binaries-default.
964 Example:
966 Environment="ONE=one" 'TWO=two two'
968 ExecStart=echo $ONE $TWO ${TWO}
969 This will execute /bin/echo with four arguments: "one", "two", "two",
971 and "two two".
972 Example:
974 Environment=ONE='one' "TWO='two two' too" THREE=
976 ExecStart=/bin/echo ${ONE} ${TWO} ${THREE}
977 ExecStart=/bin/echo $ONE $TWO $THREE
978 This results in /bin/echo being called twice, the first time with
980 arguments "'one'", "'two two' too", "", and the second time with
981 arguments "one", "two two", "too".
982 To pass a literal dollar sign, use "$$". Variables whose value is not
984 known at expansion time are treated as empty strings. Note that the
985 first argument (i.e. the program to execute) may not be a variable.
986 Variables to be used in this fashion may be defined through
988 Environment= and EnvironmentFile=. In addition, variables listed in the
989 section "Environment variables in spawned processes" in
990 systemd.exec(5), which are considered "static configuration", may be
991 used (this includes e.g. $USER, but not $TERM).
992 Note that shell command lines are not directly supported. If shell
994 command lines are to be used, they need to be passed explicitly to a
995 shell implementation of some kind. Example:
996 ExecStart=sh -c 'dmesg | tac'
998 Example:
1000 ExecStart=echo one ; echo "two two"
1002 This will execute echo two times, each time with one argument: "one"
1004 and "two two", respectively. Because two commands are specified,
1005 Type=oneshot must be used.
1006 Example:
1008 ExecStart=echo / >/dev/null & \; \
1010 ls
1011 This will execute echo with five arguments: "/", ">/dev/null", "&",
1013 ";", and "ls".
1014 Table 3. C escapes supported in command lines and environment variables
1016 ┌────────┬─────────────────────────┐
1017 │Literal │ Actual value │
1018 ├────────┼─────────────────────────┤
1019 │"\a" │ bell │
1020 ├────────┼─────────────────────────┤
1021 │"\b" │ backspace │
1022 ├────────┼─────────────────────────┤
1023 │"\f" │ form feed │
1024 ├────────┼─────────────────────────┤
1025 │"\n" │ newline │
1026 ├────────┼─────────────────────────┤
1027 │"\r" │ carriage return │
1028 ├────────┼─────────────────────────┤
1029 │"\t" │ tab │
1030 ├────────┼─────────────────────────┤
1031 │"\v" │ vertical tab │
1032 ├────────┼─────────────────────────┤
1033 │"\\" │ backslash │
1034 ├────────┼─────────────────────────┤
1035 │"\"" │ double quotation mark │
1036 ├────────┼─────────────────────────┤
1037 │"\'" │ single quotation mark │
1038 ├────────┼─────────────────────────┤
1039 │"\s" │ space │
1040 ├────────┼─────────────────────────┤
1041 │"\xxx" │ character number xx in │
1042 │ │ hexadecimal encoding │
1043 ├────────┼─────────────────────────┤
1044 │"\nnn" │ character number nnn in │
1045 │ │ octal encoding │
1046 └────────┴─────────────────────────┘
1047
1049 Example 2. Simple service
1050 The following unit file creates a service that will execute
1052 /usr/sbin/foo-daemon. Since no Type= is specified, the default
1053 Type=simple will be assumed. systemd will assume the unit to be started
1054 immediately after the program has begun executing.
1055 [Unit]
1057 Description=Foo
1058 [Service]
1060 ExecStart=/usr/sbin/foo-daemon
1061 [Install]
1063 WantedBy=multi-user.target
1064 Note that systemd assumes here that the process started by systemd will
1066 continue running until the service terminates. If the program
1067 daemonizes itself (i.e. forks), please use Type=forking instead.
1068 Since no ExecStop= was specified, systemd will send SIGTERM to all
1070 processes started from this service, and after a timeout also SIGKILL.
1071 This behavior can be modified, see systemd.kill(5) for details.
1072 Note that this unit type does not include any type of notification when
1074 a service has completed initialization. For this, you should use other
1075 unit types, such as Type=notify if the service understands systemd's
1076 notification protocol, Type=forking if the service can background
1077 itself or Type=dbus if the unit acquires a DBus name once
1078 initialization is complete. See below.
1079 Example 3. Oneshot service
1081 Sometimes, units should just execute an action without keeping active
1083 processes, such as a filesystem check or a cleanup action on boot. For
1084 this, Type=oneshot exists. Units of this type will wait until the
1085 process specified terminates and then fall back to being inactive. The
1086 following unit will perform a cleanup action:
1087 [Unit]
1089 Description=Cleanup old Foo data
1090 [Service]
1092 Type=oneshot
1093 ExecStart=/usr/sbin/foo-cleanup
1094 [Install]
1096 WantedBy=multi-user.target
1097 Note that systemd will consider the unit to be in the state "starting"
1099 until the program has terminated, so ordered dependencies will wait for
1100 the program to finish before starting themselves. The unit will revert
1101 to the "inactive" state after the execution is done, never reaching the
1102 "active" state. That means another request to start the unit will
1103 perform the action again.
1104 Type=oneshot are the only service units that may have more than one
1106 ExecStart= specified. For units with multiple commands (Type=oneshot),
1107 all commands will be run again.
1108 For Type=oneshot, Restart=always and Restart=on-success are not
1110 allowed.
1111 Example 4. Stoppable oneshot service
1113 Similarly to the oneshot services, there are sometimes units that need
1115 to execute a program to set up something and then execute another to
1116 shut it down, but no process remains active while they are considered
1117 "started". Network configuration can sometimes fall into this category.
1118 Another use case is if a oneshot service shall not be executed each
1119 time when they are pulled in as a dependency, but only the first time.
1120 For this, systemd knows the setting RemainAfterExit=yes, which causes
1122 systemd to consider the unit to be active if the start action exited
1123 successfully. This directive can be used with all types, but is most
1124 useful with Type=oneshot and Type=simple. With Type=oneshot, systemd
1125 waits until the start action has completed before it considers the unit
1126 to be active, so dependencies start only after the start action has
1127 succeeded. With Type=simple, dependencies will start immediately after
1128 the start action has been dispatched. The following unit provides an
1129 example for a simple static firewall.
1130 [Unit]
1132 Description=Simple firewall
1133 [Service]
1135 Type=oneshot
1136 RemainAfterExit=yes
1137 ExecStart=/usr/local/sbin/simple-firewall-start
1138 ExecStop=/usr/local/sbin/simple-firewall-stop
1139 [Install]
1141 WantedBy=multi-user.target
1142 Since the unit is considered to be running after the start action has
1144 exited, invoking systemctl start on that unit again will cause no
1145 action to be taken.
1146 Example 5. Traditional forking services
1148 Many traditional daemons/services background (i.e. fork, daemonize)
1150 themselves when starting. Set Type=forking in the service's unit file
1151 to support this mode of operation. systemd will consider the service to
1152 be in the process of initialization while the original program is still
1153 running. Once it exits successfully and at least a process remains (and
1154 RemainAfterExit=no), the service is considered started.
1155 Often, a traditional daemon only consists of one process. Therefore, if
1157 only one process is left after the original process terminates, systemd
1158 will consider that process the main process of the service. In that
1159 case, the $MAINPID variable will be available in ExecReload=,
1160 ExecStop=, etc.
1161 In case more than one process remains, systemd will be unable to
1163 determine the main process, so it will not assume there is one. In that
1164 case, $MAINPID will not expand to anything. However, if the process
1165 decides to write a traditional PID file, systemd will be able to read
1166 the main PID from there. Please set PIDFile= accordingly. Note that the
1167 daemon should write that file before finishing with its initialization.
1168 Otherwise, systemd might try to read the file before it exists.
1169 The following example shows a simple daemon that forks and just starts
1171 one process in the background:
1172 [Unit]
1174 Description=Some simple daemon
1175 [Service]
1177 Type=forking
1178 ExecStart=/usr/sbin/my-simple-daemon -d
1179 [Install]
1181 WantedBy=multi-user.target
1182 Please see systemd.kill(5) for details on how you can influence the way
1184 systemd terminates the service.
1185 Example 6. DBus services
1187 For services that acquire a name on the DBus system bus, use Type=dbus
1189 and set BusName= accordingly. The service should not fork (daemonize).
1190 systemd will consider the service to be initialized once the name has
1191 been acquired on the system bus. The following example shows a typical
1192 DBus service:
1193 [Unit]
1195 Description=Simple DBus service
1196 [Service]
1198 Type=dbus
1199 BusName=org.example.simple-dbus-service
1200 ExecStart=/usr/sbin/simple-dbus-service
1201 [Install]
1203 WantedBy=multi-user.target
1204 For bus-activatable services, do not include a "[Install]" section in
1206 the systemd service file, but use the SystemdService= option in the
1207 corresponding DBus service file, for example
1208 (/usr/share/dbus-1/system-services/org.example.simple-dbus-service.service):
1209 [D-BUS Service]
1211 Name=org.example.simple-dbus-service
1212 Exec=/usr/sbin/simple-dbus-service
1213 User=root
1214 SystemdService=simple-dbus-service.service
1215 Please see systemd.kill(5) for details on how you can influence the way
1217 systemd terminates the service.
1218 Example 7. Services that notify systemd about their initialization
1220 Type=simple services are really easy to write, but have the major
1222 disadvantage of systemd not being able to tell when initialization of
1223 the given service is complete. For this reason, systemd supports a
1224 simple notification protocol that allows daemons to make systemd aware
1225 that they are done initializing. Use Type=notify for this. A typical
1226 service file for such a daemon would look like this:
1227 [Unit]
1229 Description=Simple notifying service
1230 [Service]
1232 Type=notify
1233 ExecStart=/usr/sbin/simple-notifying-service
1234 [Install]
1236 WantedBy=multi-user.target
1237 Note that the daemon has to support systemd's notification protocol,
1239 else systemd will think the service has not started yet and kill it
1240 after a timeout. For an example of how to update daemons to support
1241 this protocol transparently, take a look at sd_notify(3). systemd will
1242 consider the unit to be in the 'starting' state until a readiness
1243 notification has arrived.
1244 Please see systemd.kill(5) for details on how you can influence the way
1246 systemd terminates the service.
1247
1249 systemd(1), systemctl(1), systemd-system.conf(5), systemd.unit(5),
1250 systemd.exec(5), systemd.resource-control(5), systemd.kill(5),
1251 systemd.directives(7), systemd-run(1)
1252
1254 1. Incompatibilities with SysV
1255 https://www.freedesktop.org/wiki/Software/systemd/Incompatibilities
1256 2. USB FunctionFS
1258 https://www.kernel.org/doc/Documentation/usb/functionfs.txt
1259systemd 245 SYSTEMD.SERVICE(5)