1SYSTEMD.SPECIAL(7) systemd.special SYSTEMD.SPECIAL(7)
2
6 systemd.special - Special systemd units
7
9 basic.target, bluetooth.target, cryptsetup-pre.target,
10 cryptsetup.target, ctrl-alt-del.target, boot-complete.target,
11 default.target, emergency.target, exit.target, final.target,
12 getty.target, getty-pre.target, graphical.target, halt.target,
13 hibernate.target, hybrid-sleep.target, suspend-then-hibernate.target,
14 initrd-fs.target, initrd-root-device.target, initrd-root-fs.target,
15 kbrequest.target, kexec.target, local-fs-pre.target, local-fs.target,
16 machines.target multi-user.target, network-online.target,
17 network-pre.target, network.target, nss-lookup.target,
18 nss-user-lookup.target, paths.target, poweroff.target, printer.target,
19 reboot.target, remote-cryptsetup.target, remote-fs-pre.target,
20 remote-fs.target, rescue.target, rpcbind.target, runlevel2.target,
21 runlevel3.target, runlevel4.target, runlevel5.target, shutdown.target,
22 sigpwr.target, sleep.target, slices.target, smartcard.target,
23 sockets.target, sound.target, suspend.target, swap.target,
24 sysinit.target, system-update.target, system-update-pre.target,
25 time-sync.target, timers.target, umount.target, -.slice, system.slice,
26 user.slice, machine.slice, -.mount, dbus.service, dbus.socket,
27 display-manager.service, init.scope, syslog.socket,
28 system-update-cleanup.service
29
31 A few units are treated specially by systemd. Many of them have special
32 internal semantics and cannot be renamed, while others simply have a
33 standard meaning and should be present on all systems.
34
36 Special System Units
37 -.mount
38 The root mount point, i.e. the mount unit for the / path. This unit
39 is unconditionally active, during the entire time the system is up,
40 as this mount point is where the basic userspace is running from.
41 basic.target
43 A special target unit covering basic boot-up.
44 systemd automatically adds dependency of the type After= for this
46 target unit to all services (except for those with
47 DefaultDependencies=no).
48 Usually, this should pull-in all local mount points plus /var, /tmp
50 and /var/tmp, swap devices, sockets, timers, path units and other
51 basic initialization necessary for general purpose daemons. The
52 mentioned mount points are special cased to allow them to be
53 remote.
54 This target usually does not pull in any non-target units directly,
56 but rather does so indirectly via other early boot targets. It is
57 instead meant as a synchronization point for late boot services.
58 Refer to bootup(7) for details on the targets involved.
59 boot-complete.target
61 This target is intended as generic synchronization point for
62 services that shall determine or act on whether the boot process
63 completed successfully. Order units that are required to succeed
64 for a boot process to be considered successful before this unit,
65 and add a Requires= dependency from the target unit to them. Order
66 units that shall only run when the boot process is considered
67 successful after the target unit and pull in the target from it,
68 also with Requires=. Note that by default this target unit is not
69 part of the initial boot transaction, but is supposed to be pulled
70 in only if required by units that want to run only on successful
71 boots.
72 See systemd-boot-check-no-failures.service(8) for a service that
74 implements a generic system health check and orders itself before
75 boot-complete.target.
76 See systemd-bless-boot.service(8) for a service that propagates
78 boot success information to the boot loader, and orders itself
79 after boot-complete.target.
80 ctrl-alt-del.target
82 systemd starts this target whenever Control+Alt+Del is pressed on
83 the console. Usually, this should be aliased (symlinked) to
84 reboot.target.
85 cryptsetup.target
87 A target that pulls in setup services for all encrypted block
88 devices.
89 dbus.service
91 A special unit for the D-Bus bus daemon. As soon as this service is
92 fully started up systemd will connect to it and register its
93 service.
94 dbus.socket
96 A special unit for the D-Bus system bus socket. All units with
97 Type=dbus automatically gain a dependency on this unit.
98 default.target
100 The default unit systemd starts at bootup. Usually, this should be
101 aliased (symlinked) to multi-user.target or graphical.target.
102 The default unit systemd starts at bootup can be overridden with
104 the systemd.unit= kernel command line option.
105 display-manager.service
107 The display manager service. Usually, this should be aliased
108 (symlinked) to gdm.service or a similar display manager service.
109 emergency.target
111 A special target unit that starts an emergency shell on the main
112 console. This target does not pull in any services or mounts. It is
113 the most minimal version of starting the system in order to acquire
114 an interactive shell; the only processes running are usually just
115 the system manager (PID 1) and the shell process. This unit is
116 supposed to be used with the kernel command line option
117 systemd.unit=; it is also used when a file system check on a
118 required file system fails, and boot-up cannot continue. Compare
119 with rescue.target, which serves a similar purpose, but also starts
120 the most basic services and mounts all file systems.
121 Use the "systemd.unit=emergency.target" kernel command line option
123 to boot into this mode. A short alias for this kernel command line
124 option is "emergency", for compatibility with SysV.
125 In many ways booting into emergency.target is similar to the effect
127 of booting with "init=/bin/sh" on the kernel command line, except
128 that emergency mode provides you with the full system and service
129 manager, and allows starting individual units in order to continue
130 the boot process in steps.
131 exit.target
133 A special service unit for shutting down the system or user service
134 manager. It is equivalent to poweroff.target on non-container
135 systems, and also works in containers.
136 systemd will start this unit when it receives the SIGTERM or SIGINT
138 signal when running as user service daemon.
139 Normally, this (indirectly) pulls in shutdown.target, which in turn
141 should be conflicted by all units that want to be scheduled for
142 shutdown when the service manager starts to exit.
143 final.target
145 A special target unit that is used during the shutdown logic and
146 may be used to pull in late services after all normal services are
147 already terminated and all mounts unmounted.
148 getty.target
150 A special target unit that pulls in statically configured local TTY
151 getty instances.
152 graphical.target
154 A special target unit for setting up a graphical login screen. This
155 pulls in multi-user.target.
156 Units that are needed for graphical logins shall add Wants=
158 dependencies for their unit to this unit (or multi-user.target)
159 during installation. This is best configured via
160 WantedBy=graphical.target in the unit's "[Install]" section.
161 hibernate.target
163 A special target unit for hibernating the system. This pulls in
164 sleep.target.
165 hybrid-sleep.target
167 A special target unit for hibernating and suspending the system at
168 the same time. This pulls in sleep.target.
169 suspend-then-hibernate.target
171 A special target unit for suspending the system for a period of
172 time, waking it and putting it into hibernate. This pulls in
173 sleep.target.
174 halt.target
176 A special target unit for shutting down and halting the system.
177 Note that this target is distinct from poweroff.target in that it
178 generally really just halts the system rather than powering it
179 down.
180 Applications wanting to halt the system should not start this unit
182 directly, but should instead execute systemctl halt (possibly with
183 the --no-block option) or call systemd(1)'s
184 org.freedesktop.systemd1.Manager.Halt D-Bus method directly.
185 init.scope
187 This scope unit is where the system and service manager (PID 1)
188 itself resides. It is active as long as the system is running.
189 initrd-fs.target
191 systemd-fstab-generator(3) automatically adds dependencies of type
192 Before= to sysroot-usr.mount and all mount points found in
193 /etc/fstab that have x-initrd.mount and not have noauto mount
194 options set.
195 initrd-root-device.target
197 A special initrd target unit that is reached when the root
198 filesystem device is available, but before it has been mounted.
199 systemd-fstab-generator(3) and systemd-gpt-auto-generator(3)
200 automatically setup the appropriate dependencies to make this
201 happen.
202 initrd-root-fs.target
204 systemd-fstab-generator(3) automatically adds dependencies of type
205 Before= to the sysroot.mount unit, which is generated from the
206 kernel command line.
207 kbrequest.target
209 systemd starts this target whenever Alt+ArrowUp is pressed on the
210 console. Note that any user with physical access to the machine
211 will be able to do this, without authentication, so this should be
212 used carefully.
213 kexec.target
215 A special target unit for shutting down and rebooting the system
216 via kexec.
217 Applications wanting to reboot the system should not start this
219 unit directly, but should instead execute systemctl kexec (possibly
220 with the --no-block option) or call systemd(1)'s
221 org.freedesktop.systemd1.Manager.KExec D-Bus method directly.
222 local-fs.target
224 systemd-fstab-generator(3) automatically adds dependencies of type
225 Before= to all mount units that refer to local mount points for
226 this target unit. In addition, it adds dependencies of type Wants=
227 to this target unit for those mounts listed in /etc/fstab that have
228 the auto mount option set.
229 machines.target
231 A standard target unit for starting all the containers and other
232 virtual machines. See systemd-nspawn@.service for an example.
233 multi-user.target
235 A special target unit for setting up a multi-user system
236 (non-graphical). This is pulled in by graphical.target.
237 Units that are needed for a multi-user system shall add Wants=
239 dependencies for their unit to this unit during installation. This
240 is best configured via WantedBy=multi-user.target in the unit's
241 "[Install]" section.
242 network-online.target
244 Units that strictly require a configured network connection should
245 pull in network-online.target (via a Wants= type dependency) and
246 order themselves after it. This target unit is intended to pull in
247 a service that delays further execution until the network is
248 sufficiently set up. What precisely this requires is left to the
249 implementation of the network managing service.
250 Note the distinction between this unit and network.target. This
252 unit is an active unit (i.e. pulled in by the consumer rather than
253 the provider of this functionality) and pulls in a service which
254 possibly adds substantial delays to further execution. In contrast,
255 network.target is a passive unit (i.e. pulled in by the provider of
256 the functionality, rather than the consumer) that usually does not
257 delay execution much. Usually, network.target is part of the boot
258 of most systems, while network-online.target is not, except when at
259 least one unit requires it. Also see Running Services After the
260 Network is up[1] for more information.
261 All mount units for remote network file systems automatically pull
263 in this unit, and order themselves after it. Note that networking
264 daemons that simply provide functionality to other hosts generally
265 do not need to pull this in.
266 systemd automatically adds dependencies of type Wants= and After=
268 for this target unit to all SysV init script service units with an
269 LSB header referring to the "$network" facility.
270 Note that this unit is only useful during the original system
272 start-up logic. After the system has completed booting up, it will
273 not track the online state of the system anymore. Due to this it
274 cannot be used as a network connection monitor concept, it is
275 purely a one-time system start-up concept.
276 paths.target
278 A special target unit that sets up all path units (see
279 systemd.path(5) for details) that shall be active after boot.
280 It is recommended that path units installed by applications get
282 pulled in via Wants= dependencies from this unit. This is best
283 configured via a WantedBy=paths.target in the path unit's
284 "[Install]" section.
285 poweroff.target
287 A special target unit for shutting down and powering off the
288 system.
289 Applications wanting to power off the system should not start this
291 unit directly, but should instead execute systemctl poweroff
292 (possibly with the --no-block option) or call systemd-logind(8)'s
293 org.freedesktop.login1.Manager.PowerOff D-Bus method directly.
294 runlevel0.target is an alias for this target unit, for
296 compatibility with SysV.
297 reboot.target
299 A special target unit for shutting down and rebooting the system.
300 Applications wanting to reboot the system should not start this
302 unit directly, but should instead execute systemctl reboot
303 (possibly with the --no-block option) or call systemd-logind(8)'s
304 org.freedesktop.login1.Manager.Reboot D-Bus method directly.
305 runlevel6.target is an alias for this target unit, for
307 compatibility with SysV.
308 remote-cryptsetup.target
310 Similar to cryptsetup.target, but for encrypted devices which are
311 accessed over the network. It is used for crypttab(8) entries
312 marked with _netdev.
313 remote-fs.target
315 Similar to local-fs.target, but for remote mount points.
316 systemd automatically adds dependencies of type After= for this
318 target unit to all SysV init script service units with an LSB
319 header referring to the "$remote_fs" facility.
320 rescue.target
322 A special target unit that pulls in the base system (including
323 system mounts) and spawns a rescue shell. Isolate to this target in
324 order to administer the system in single-user mode with all file
325 systems mounted but with no services running, except for the most
326 basic. Compare with emergency.target, which is much more reduced
327 and does not provide the file systems or most basic services.
328 Compare with multi-user.target, this target could be seen as
329 single-user.target.
330 runlevel1.target is an alias for this target unit, for
332 compatibility with SysV.
333 Use the "systemd.unit=rescue.target" kernel command line option to
335 boot into this mode. A short alias for this kernel command line
336 option is "1", for compatibility with SysV.
337 runlevel2.target, runlevel3.target, runlevel4.target, runlevel5.target
339 These are targets that are called whenever the SysV compatibility
340 code asks for runlevel 2, 3, 4, 5, respectively. It is a good idea
341 to make this an alias for (i.e. symlink to) graphical.target (for
342 runlevel 5) or multi-user.target (the others).
343 shutdown.target
345 A special target unit that terminates the services on system
346 shutdown.
347 Services that shall be terminated on system shutdown shall add
349 Conflicts= and Before= dependencies to this unit for their service
350 unit, which is implicitly done when DefaultDependencies=yes is set
351 (the default).
352 sigpwr.target
354 A special target that is started when systemd receives the SIGPWR
355 process signal, which is normally sent by the kernel or UPS daemons
356 when power fails.
357 sleep.target
359 A special target unit that is pulled in by suspend.target,
360 hibernate.target and hybrid-sleep.target and may be used to hook
361 units into the sleep state logic.
362 slices.target
364 A special target unit that sets up all slice units (see
365 systemd.slice(5) for details) that shall always be active after
366 boot. By default the generic system.slice slice unit as well as the
367 root slice unit -.slice are pulled in and ordered before this unit
368 (see below).
369 Adding slice units to slices.target is generally not necessary.
371 Instead, when some unit that uses Slice= is started, the specified
372 slice will be started automatically. Adding WantedBy=slices.target
373 lines to the "[Install]" section should only be done for units that
374 need to be always active. In that case care needs to be taken to
375 avoid creating a loop through the automatic dependencies on
376 "parent" slices.
377 sockets.target
379 A special target unit that sets up all socket units (see
380 systemd.socket(5) for details) that shall be active after boot.
381 Services that can be socket-activated shall add Wants= dependencies
383 to this unit for their socket unit during installation. This is
384 best configured via a WantedBy=sockets.target in the socket unit's
385 "[Install]" section.
386 suspend.target
388 A special target unit for suspending the system. This pulls in
389 sleep.target.
390 swap.target
392 Similar to local-fs.target, but for swap partitions and swap files.
393 sysinit.target
395 systemd automatically adds dependencies of the types Requires= and
396 After= for this target unit to all services (except for those with
397 DefaultDependencies=no).
398 This target pulls in the services required for system
400 initialization. System services pulled in by this target should
401 declare DefaultDependencies=no and specify all their dependencies
402 manually, including access to anything more than a read only root
403 filesystem. For details on the dependencies of this target, refer
404 to bootup(7).
405 syslog.socket
407 The socket unit syslog implementations should listen on. All
408 userspace log messages will be made available on this socket. For
409 more information about syslog integration, please consult the
410 Syslog Interface[2] document.
411 system-update.target, system-update-pre.target,
413 system-update-cleanup.service
414 A special target unit that is used for offline system updates.
415 systemd-system-update-generator(8) will redirect the boot process
416 to this target if /system-update exists. For more information see
417 systemd.offline-updates(7).
418 Updates should happen before the system-update.target is reached,
420 and the services which implement them should cause the machine to
421 reboot. The main units executing the update should order themselves
422 after system-update-pre.target but not pull it in. Services which
423 want to run during system updates only, but before the actual
424 system update is executed should order themselves before this unit
425 and pull it in. As a safety measure, if this does not happen, and
426 /system-update still exists after system-update.target is reached,
427 system-update-cleanup.service will remove this symlink and reboot
428 the machine.
429 timers.target
431 A special target unit that sets up all timer units (see
432 systemd.timer(5) for details) that shall be active after boot.
433 It is recommended that timer units installed by applications get
435 pulled in via Wants= dependencies from this unit. This is best
436 configured via WantedBy=timers.target in the timer unit's
437 "[Install]" section.
438 umount.target
440 A special target unit that unmounts all mount and automount points
441 on system shutdown.
442 Mounts that shall be unmounted on system shutdown shall add
444 Conflicts dependencies to this unit for their mount unit, which is
445 implicitly done when DefaultDependencies=yes is set (the default).
446 Special System Units for Devices
448 Some target units are automatically pulled in as devices of certain
449 kinds show up in the system. These may be used to automatically
450 activate various services based on the specific type of the available
451 hardware.
452 bluetooth.target
454 This target is started automatically as soon as a Bluetooth
455 controller is plugged in or becomes available at boot.
456 This may be used to pull in Bluetooth management daemons
458 dynamically when Bluetooth hardware is found.
459 printer.target
461 This target is started automatically as soon as a printer is
462 plugged in or becomes available at boot.
463 This may be used to pull in printer management daemons dynamically
465 when printer hardware is found.
466 smartcard.target
468 This target is started automatically as soon as a smartcard
469 controller is plugged in or becomes available at boot.
470 This may be used to pull in smartcard management daemons
472 dynamically when smartcard hardware is found.
473 sound.target
475 This target is started automatically as soon as a sound card is
476 plugged in or becomes available at boot.
477 This may be used to pull in audio management daemons dynamically
479 when audio hardware is found.
480 Special Passive System Units
482 A number of special system targets are defined that can be used to
483 properly order boot-up of optional services. These targets are
484 generally not part of the initial boot transaction, unless they are
485 explicitly pulled in by one of the implementing services. Note
486 specifically that these passive target units are generally not pulled
487 in by the consumer of a service, but by the provider of the service.
488 This means: a consuming service should order itself after these targets
489 (as appropriate), but not pull it in. A providing service should order
490 itself before these targets (as appropriate) and pull it in (via a
491 Wants= type dependency).
492 Note that these passive units cannot be started manually, i.e.
494 "systemctl start time-sync.target" will fail with an error. They can
495 only be pulled in by dependency. This is enforced since they exist for
496 ordering purposes only and thus are not useful as only unit within a
497 transaction.
498 cryptsetup-pre.target
500 This passive target unit may be pulled in by services that want to
501 run before any encrypted block device is set up. All encrypted
502 block devices are set up after this target has been reached. Since
503 the shutdown order is implicitly the reverse start-up order between
504 units, this target is particularly useful to ensure that a service
505 is shut down only after all encrypted block devices are fully
506 stopped.
507 getty-pre.target
509 A special passive target unit. Users of this target are expected to
510 pull it in the boot transaction via a dependency (e.g. Wants=).
511 Order your unit before this unit if you want to make use of the
512 console just before getty is started.
513 local-fs-pre.target
515 This target unit is automatically ordered before all local mount
516 points marked with auto (see above). It can be used to execute
517 certain units before all local mounts.
518 network.target
520 This unit is supposed to indicate when network functionality is
521 available, but it is only very weakly defined what that is supposed
522 to mean, with one exception: at shutdown, a unit that is ordered
523 after network.target will be stopped before the network — to
524 whatever level it might be set up then — is shut down. It is hence
525 useful when writing service files that require network access on
526 shutdown, which should order themselves after this target, but not
527 pull it in. Also see Running Services After the Network is up[1]
528 for more information. Also see network-online.target described
529 above.
530 network-pre.target
532 This passive target unit may be pulled in by services that want to
533 run before any network is set up, for example for the purpose of
534 setting up a firewall. All network management software orders
535 itself after this target, but does not pull it in.
536 nss-lookup.target
538 A target that should be used as synchronization point for all
539 host/network name service lookups. Note that this is independent of
540 UNIX user/group name lookups for which nss-user-lookup.target
541 should be used. All services for which the availability of full
542 host/network name resolution is essential should be ordered after
543 this target, but not pull it in. systemd automatically adds
544 dependencies of type After= for this target unit to all SysV init
545 script service units with an LSB header referring to the "$named"
546 facility.
547 nss-user-lookup.target
549 A target that should be used as synchronization point for all
550 regular UNIX user/group name service lookups. Note that this is
551 independent of host/network name lookups for which
552 nss-lookup.target should be used. All services for which the
553 availability of the full user/group database is essential should be
554 ordered after this target, but not pull it in. All services which
555 provide parts of the user/group database should be ordered before
556 this target, and pull it in. Note that this unit is only relevant
557 for regular users and groups — system users and groups are required
558 to be resolvable during earliest boot already, and hence do not
559 need any special ordering against this target.
560 remote-fs-pre.target
562 This target unit is automatically ordered before all mount point
563 units (see above) and cryptsetup devices marked with the _netdev.
564 It can be used to run certain units before remote encrypted devices
565 and mounts are established. Note that this unit is generally not
566 part of the initial transaction, unless the unit that wants to be
567 ordered before all remote mounts pulls it in via a Wants= type
568 dependency. If the unit wants to be pulled in by the first remote
569 mount showing up, it should use network-online.target (see above).
570 rpcbind.target
572 The portmapper/rpcbind pulls in this target and orders itself
573 before it, to indicate its availability. systemd automatically adds
574 dependencies of type After= for this target unit to all SysV init
575 script service units with an LSB header referring to the "$portmap"
576 facility.
577 time-sync.target
579 Services responsible for synchronizing the system clock from a
580 remote source (such as NTP client implementations) should pull in
581 this target and order themselves before it. All services where
582 correct time is essential should be ordered after this unit, but
583 not pull it in. systemd automatically adds dependencies of type
584 After= for this target unit to all SysV init script service units
585 with an LSB header referring to the "$time" facility.
586 Special Slice Units
588 There are four ".slice" units which form the basis of the hierarchy for
589 assignment of resources for services, users, and virtual machines or
590 containers. See systemd.slice(7) for details about slice units.
591 -.slice
593 The root slice is the root of the slice hierarchy. It usually does
594 not contain units directly, but may be used to set defaults for the
595 whole tree.
596 system.slice
598 By default, all system services started by systemd are found in
599 this slice.
600 user.slice
602 By default, all user processes and services started on behalf of
603 the user, including the per-user systemd instance are found in this
604 slice. This is pulled in by systemd-logind.service
605 machine.slice
607 By default, all virtual machines and containers registered with
608 systemd-machined are found in this slice. This is pulled in by
609 systemd-machined.service
610
612 Special User Units
613 When systemd runs as a user instance, the following special units are
614 available:
615 default.target
617 This is the main target of the user session, started by default.
618 Various services that compose the normal user session should be
619 pulled into this target. In this regard, default.target is similar
620 to multi-user.target in the system instance, but it is a real unit,
621 not an alias.
622 In addition, the following units are available which have definitions
624 similar to their system counterparts: exit.target, shutdown.target,
625 sockets.target, timers.target, paths.target, bluetooth.target,
626 printer.target, smartcard.target, sound.target.
627 Special Passive User Units
629 graphical-session.target
630 This target is active whenever any graphical session is running. It
631 is used to stop user services which only apply to a graphical (X,
632 Wayland, etc.) session when the session is terminated. Such
633 services should have "PartOf=graphical-session.target" in their
634 "[Unit]" section. A target for a particular session (e. g.
635 gnome-session.target) starts and stops "graphical-session.target"
636 with "BindsTo=graphical-session.target".
637 Which services are started by a session target is determined by the
639 "Wants=" and "Requires=" dependencies. For services that can be
640 enabled independently, symlinks in ".wants/" and ".requires/"
641 should be used, see systemd.unit(5). Those symlinks should either
642 be shipped in packages, or should be added dynamically after
643 installation, for example using "systemctl add-wants", see
644 systemctl(1).
645 Example 1. Nautilus as part of a GNOME session
647 "gnome-session.target" pulls in Nautilus as top-level service:
648 [Unit]
650 Description=User systemd services for GNOME graphical session
651 Wants=nautilus.service
652 BindsTo=graphical-session.target
653 "nautilus.service" gets stopped when the session stops:
655 [Unit]
657 Description=Render the desktop icons with Nautilus
658 PartOf=graphical-session.target
659 [Service]
661 ...
662 graphical-session-pre.target
664 This target contains services which set up the environment or
665 global configuration of a graphical session, such as SSH/GPG agents
666 (which need to export an environment variable into all desktop
667 processes) or migration of obsolete d-conf keys after an OS upgrade
668 (which needs to happen before starting any process that might use
669 them). This target must be started before starting a graphical
670 session like gnome-session.target.
671
673 systemd(1), systemd.unit(5), systemd.service(5), systemd.socket(5),
674 systemd.target(5), systemd.slice(5), bootup(7), systemd-fstab-
675 generator(8), user@.service(5)
676
678 1. Running Services After the Network is up
679 https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget
680 2. Syslog Interface
682 https://www.freedesktop.org/wiki/Software/systemd/syslog
683systemd 241 SYSTEMD.SPECIAL(7)