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, default.target,
11 emergency.target, exit.target, final.target, getty.target,
12 getty-pre.target, graphical.target, halt.target, hibernate.target,
13 hybrid-sleep.target, suspend-then-hibernate.target, initrd-fs.target,
14 initrd-root-device.target, initrd-root-fs.target, kbrequest.target,
15 kexec.target, local-fs-pre.target, local-fs.target, machines.target
16 multi-user.target, network-online.target, network-pre.target,
17 network.target, nss-lookup.target, nss-user-lookup.target,
18 paths.target, poweroff.target, printer.target, reboot.target,
19 remote-cryptsetup.target, remote-fs-pre.target, remote-fs.target,
20 rescue.target, rpcbind.target, runlevel2.target, runlevel3.target,
21 runlevel4.target, runlevel5.target, shutdown.target, sigpwr.target,
22 sleep.target, slices.target, smartcard.target, sockets.target,
23 sound.target, suspend.target, swap.target, sysinit.target,
24 system-update.target, system-update-pre.target, time-sync.target,
25 timers.target, umount.target, -.slice, system.slice, user.slice,
26 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 -.mount
37 The root mount point, i.e. the mount unit for the / path. This unit
38 is unconditionally active, during the entire time the system is up,
39 as this mount point is where the basic userspace is running from.
40 basic.target
42 A special target unit covering basic boot-up.
43 systemd automatically adds dependency of the type After= for this
45 target unit to all services (except for those with
46 DefaultDependencies=no).
47 Usually, this should pull-in all local mount points plus /var, /tmp
49 and /var/tmp, swap devices, sockets, timers, path units and other
50 basic initialization necessary for general purpose daemons. The
51 mentioned mount points are special cased to allow them to be
52 remote.
53 This target usually does not pull in any non-target units directly,
55 but rather does so indirectly via other early boot targets. It is
56 instead meant as a synchronization point for late boot services.
57 Refer to bootup(7) for details on the targets involved.
58 ctrl-alt-del.target
60 systemd starts this target whenever Control+Alt+Del is pressed on
61 the console. Usually, this should be aliased (symlinked) to
62 reboot.target.
63 cryptsetup.target
65 A target that pulls in setup services for all encrypted block
66 devices.
67 dbus.service
69 A special unit for the D-Bus bus daemon. As soon as this service is
70 fully started up systemd will connect to it and register its
71 service.
72 dbus.socket
74 A special unit for the D-Bus system bus socket. All units with
75 Type=dbus automatically gain a dependency on this unit.
76 default.target
78 The default unit systemd starts at bootup. Usually, this should be
79 aliased (symlinked) to multi-user.target or graphical.target.
80 The default unit systemd starts at bootup can be overridden with
82 the systemd.unit= kernel command line option.
83 display-manager.service
85 The display manager service. Usually, this should be aliased
86 (symlinked) to gdm.service or a similar display manager service.
87 emergency.target
89 A special target unit that starts an emergency shell on the main
90 console. This target does not pull in any services or mounts. It is
91 the most minimal version of starting the system in order to acquire
92 an interactive shell; the only processes running are usually just
93 the system manager (PID 1) and the shell process. This unit is
94 supposed to be used with the kernel command line option
95 systemd.unit=; it is also used when a file system check on a
96 required file system fails, and boot-up cannot continue. Compare
97 with rescue.target, which serves a similar purpose, but also starts
98 the most basic services and mounts all file systems.
99 Use the "systemd.unit=emergency.target" kernel command line option
101 to boot into this mode. A short alias for this kernel command line
102 option is "emergency", for compatibility with SysV.
103 In many ways booting into emergency.target is similar to the effect
105 of booting with "init=/bin/sh" on the kernel command line, except
106 that emergency mode provides you with the full system and service
107 manager, and allows starting individual units in order to continue
108 the boot process in steps.
109 exit.target
111 A special service unit for shutting down the system or user service
112 manager. It is equivalent to poweroff.target on non-container
113 systems, and also works in containers.
114 systemd will start this unit when it receives the SIGTERM or SIGINT
116 signal when running as user service daemon.
117 Normally, this (indirectly) pulls in shutdown.target, which in turn
119 should be conflicted by all units that want to be scheduled for
120 shutdown when the service manager starts to exit.
121 final.target
123 A special target unit that is used during the shutdown logic and
124 may be used to pull in late services after all normal services are
125 already terminated and all mounts unmounted.
126 getty.target
128 A special target unit that pulls in statically configured local TTY
129 getty instances.
130 graphical.target
132 A special target unit for setting up a graphical login screen. This
133 pulls in multi-user.target.
134 Units that are needed for graphical logins shall add Wants=
136 dependencies for their unit to this unit (or multi-user.target)
137 during installation. This is best configured via
138 WantedBy=graphical.target in the unit's "[Install]" section.
139 hibernate.target
141 A special target unit for hibernating the system. This pulls in
142 sleep.target.
143 hybrid-sleep.target
145 A special target unit for hibernating and suspending the system at
146 the same time. This pulls in sleep.target.
147 suspend-then-hibernate.target
149 A special target unit for suspending the system for a period of
150 time, waking it and putting it into hibernate. This pulls in
151 sleep.target.
152 halt.target
154 A special target unit for shutting down and halting the system.
155 Note that this target is distinct from poweroff.target in that it
156 generally really just halts the system rather than powering it
157 down.
158 Applications wanting to halt the system should not start this unit
160 directly, but should instead execute systemctl halt (possibly with
161 the --no-block option) or call systemd(1)'s
162 org.freedesktop.systemd1.Manager.Halt D-Bus method directly.
163 init.scope
165 This scope unit is where the system and service manager (PID 1)
166 itself resides. It is active as long as the system is running.
167 initrd-fs.target
169 systemd-fstab-generator(3) automatically adds dependencies of type
170 Before= to sysroot-usr.mount and all mount points found in
171 /etc/fstab that have x-initrd.mount and not have noauto mount
172 options set.
173 initrd-root-device.target
175 A special initrd target unit that is reached when the root
176 filesystem device is available, but before it has been mounted.
177 systemd-fstab-generator(3) and systemd-gpt-auto-generator(3)
178 automatically setup the appropriate dependencies to make this
179 happen.
180 initrd-root-fs.target
182 systemd-fstab-generator(3) automatically adds dependencies of type
183 Before= to the sysroot.mount unit, which is generated from the
184 kernel command line.
185 kbrequest.target
187 systemd starts this target whenever Alt+ArrowUp is pressed on the
188 console. Note that any user with physical access to the machine
189 will be able to do this, without authentication, so this should be
190 used carefully.
191 kexec.target
193 A special target unit for shutting down and rebooting the system
194 via kexec.
195 Applications wanting to reboot the system should not start this
197 unit directly, but should instead execute systemctl kexec (possibly
198 with the --no-block option) or call systemd(1)'s
199 org.freedesktop.systemd1.Manager.KExec D-Bus method directly.
200 local-fs.target
202 systemd-fstab-generator(3) automatically adds dependencies of type
203 Before= to all mount units that refer to local mount points for
204 this target unit. In addition, it adds dependencies of type Wants=
205 to this target unit for those mounts listed in /etc/fstab that have
206 the auto mount option set.
207 machines.target
209 A standard target unit for starting all the containers and other
210 virtual machines. See systemd-nspawn@.service for an example.
211 multi-user.target
213 A special target unit for setting up a multi-user system
214 (non-graphical). This is pulled in by graphical.target.
215 Units that are needed for a multi-user system shall add Wants=
217 dependencies for their unit to this unit during installation. This
218 is best configured via WantedBy=multi-user.target in the unit's
219 "[Install]" section.
220 network-online.target
222 Units that strictly require a configured network connection should
223 pull in network-online.target (via a Wants= type dependency) and
224 order themselves after it. This target unit is intended to pull in
225 a service that delays further execution until the network is
226 sufficiently set up. What precisely this requires is left to the
227 implementation of the network managing service.
228 Note the distinction between this unit and network.target. This
230 unit is an active unit (i.e. pulled in by the consumer rather than
231 the provider of this functionality) and pulls in a service which
232 possibly adds substantial delays to further execution. In contrast,
233 network.target is a passive unit (i.e. pulled in by the provider of
234 the functionality, rather than the consumer) that usually does not
235 delay execution much. Usually, network.target is part of the boot
236 of most systems, while network-online.target is not, except when at
237 least one unit requires it. Also see Running Services After the
238 Network is up[1] for more information.
239 All mount units for remote network file systems automatically pull
241 in this unit, and order themselves after it. Note that networking
242 daemons that simply provide functionality to other hosts generally
243 do not need to pull this in.
244 systemd automatically adds dependencies of type Wants= and After=
246 for this target unit to all SysV init script service units with an
247 LSB header referring to the "$network" facility.
248 Note that this unit is only useful during the original system
250 start-up logic. After the system has completed booting up, it will
251 not track the online state of the system anymore. Due to this it
252 cannot be used as a network connection monitor concept, it is
253 purely a one-time system start-up concept.
254 paths.target
256 A special target unit that sets up all path units (see
257 systemd.path(5) for details) that shall be active after boot.
258 It is recommended that path units installed by applications get
260 pulled in via Wants= dependencies from this unit. This is best
261 configured via a WantedBy=paths.target in the path unit's
262 "[Install]" section.
263 poweroff.target
265 A special target unit for shutting down and powering off the
266 system.
267 Applications wanting to power off the system should not start this
269 unit directly, but should instead execute systemctl poweroff
270 (possibly with the --no-block option) or call systemd-logind(8)'s
271 org.freedesktop.login1.Manager.PowerOff D-Bus method directly.
272 runlevel0.target is an alias for this target unit, for
274 compatibility with SysV.
275 reboot.target
277 A special target unit for shutting down and rebooting the system.
278 Applications wanting to reboot the system should not start this
280 unit directly, but should instead execute systemctl reboot
281 (possibly with the --no-block option) or call systemd-logind(8)'s
282 org.freedesktop.login1.Manager.Reboot D-Bus method directly.
283 runlevel6.target is an alias for this target unit, for
285 compatibility with SysV.
286 remote-cryptsetup.target
288 Similar to cryptsetup.target, but for encrypted devices which are
289 accessed over the network. It is used for crypttab(8) entries
290 marked with _netdev.
291 remote-fs.target
293 Similar to local-fs.target, but for remote mount points.
294 systemd automatically adds dependencies of type After= for this
296 target unit to all SysV init script service units with an LSB
297 header referring to the "$remote_fs" facility.
298 rescue.target
300 A special target unit that pulls in the base system (including
301 system mounts) and spawns a rescue shell. Isolate to this target in
302 order to administer the system in single-user mode with all file
303 systems mounted but with no services running, except for the most
304 basic. Compare with emergency.target, which is much more reduced
305 and does not provide the file systems or most basic services.
306 Compare with multi-user.target, this target could be seen as
307 single-user.target.
308 runlevel1.target is an alias for this target unit, for
310 compatibility with SysV.
311 Use the "systemd.unit=rescue.target" kernel command line option to
313 boot into this mode. A short alias for this kernel command line
314 option is "1", for compatibility with SysV.
315 runlevel2.target, runlevel3.target, runlevel4.target, runlevel5.target
317 These are targets that are called whenever the SysV compatibility
318 code asks for runlevel 2, 3, 4, 5, respectively. It is a good idea
319 to make this an alias for (i.e. symlink to) graphical.target (for
320 runlevel 5) or multi-user.target (the others).
321 shutdown.target
323 A special target unit that terminates the services on system
324 shutdown.
325 Services that shall be terminated on system shutdown shall add
327 Conflicts= and Before= dependencies to this unit for their service
328 unit, which is implicitly done when DefaultDependencies=yes is set
329 (the default).
330 sigpwr.target
332 A special target that is started when systemd receives the SIGPWR
333 process signal, which is normally sent by the kernel or UPS daemons
334 when power fails.
335 sleep.target
337 A special target unit that is pulled in by suspend.target,
338 hibernate.target and hybrid-sleep.target and may be used to hook
339 units into the sleep state logic.
340 slices.target
342 A special target unit that sets up all slice units (see
343 systemd.slice(5) for details) that shall be active after boot. By
344 default the generic system.slice slice unit, as well as the root
345 slice unit -.slice, is pulled in and ordered before this unit (see
346 below).
347 It's a good idea to add WantedBy=slices.target lines to the
349 "[Install]" section of all slices units that may be installed
350 dynamically.
351 sockets.target
353 A special target unit that sets up all socket units (see
354 systemd.socket(5) for details) that shall be active after boot.
355 Services that can be socket-activated shall add Wants= dependencies
357 to this unit for their socket unit during installation. This is
358 best configured via a WantedBy=sockets.target in the socket unit's
359 "[Install]" section.
360 suspend.target
362 A special target unit for suspending the system. This pulls in
363 sleep.target.
364 swap.target
366 Similar to local-fs.target, but for swap partitions and swap files.
367 sysinit.target
369 systemd automatically adds dependencies of the types Requires= and
370 After= for this target unit to all services (except for those with
371 DefaultDependencies=no).
372 This target pulls in the services required for system
374 initialization. System services pulled in by this target should
375 declare DefaultDependencies=no and specify all their dependencies
376 manually, including access to anything more than a read only root
377 filesystem. For details on the dependencies of this target, refer
378 to bootup(7).
379 syslog.socket
381 The socket unit syslog implementations should listen on. All
382 userspace log messages will be made available on this socket. For
383 more information about syslog integration, please consult the
384 Syslog Interface[2] document.
385 system-update.target, system-update-pre.target,
387 system-update-cleanup.service
388 A special target unit that is used for offline system updates.
389 systemd-system-update-generator(8) will redirect the boot process
390 to this target if /system-update exists. For more information see
391 systemd.offline-updates(7).
392 Updates should happen before the system-update.target is reached,
394 and the services which implement them should cause the machine to
395 reboot. The main units executing the update should order themselves
396 after system-update-pre.target but not pull it in. Services which
397 want to run during system updates only, but before the actual
398 system update is executed should order themselves before this unit
399 and pull it in. As a safety measure, if this does not happen, and
400 /system-update still exists after system-update.target is reached,
401 system-update-cleanup.service will remove this symlink and reboot
402 the machine.
403 timers.target
405 A special target unit that sets up all timer units (see
406 systemd.timer(5) for details) that shall be active after boot.
407 It is recommended that timer units installed by applications get
409 pulled in via Wants= dependencies from this unit. This is best
410 configured via WantedBy=timers.target in the timer unit's
411 "[Install]" section.
412 umount.target
414 A special target unit that unmounts all mount and automount points
415 on system shutdown.
416 Mounts that shall be unmounted on system shutdown shall add
418 Conflicts dependencies to this unit for their mount unit, which is
419 implicitly done when DefaultDependencies=yes is set (the default).
420
422 Some target units are automatically pulled in as devices of certain
423 kinds show up in the system. These may be used to automatically
424 activate various services based on the specific type of the available
425 hardware.
426 bluetooth.target
428 This target is started automatically as soon as a Bluetooth
429 controller is plugged in or becomes available at boot.
430 This may be used to pull in Bluetooth management daemons
432 dynamically when Bluetooth hardware is found.
433 printer.target
435 This target is started automatically as soon as a printer is
436 plugged in or becomes available at boot.
437 This may be used to pull in printer management daemons dynamically
439 when printer hardware is found.
440 smartcard.target
442 This target is started automatically as soon as a smartcard
443 controller is plugged in or becomes available at boot.
444 This may be used to pull in smartcard management daemons
446 dynamically when smartcard hardware is found.
447 sound.target
449 This target is started automatically as soon as a sound card is
450 plugged in or becomes available at boot.
451 This may be used to pull in audio management daemons dynamically
453 when audio hardware is found.
454
456 A number of special system targets are defined that can be used to
457 properly order boot-up of optional services. These targets are
458 generally not part of the initial boot transaction, unless they are
459 explicitly pulled in by one of the implementing services. Note
460 specifically that these passive target units are generally not pulled
461 in by the consumer of a service, but by the provider of the service.
462 This means: a consuming service should order itself after these targets
463 (as appropriate), but not pull it in. A providing service should order
464 itself before these targets (as appropriate) and pull it in (via a
465 Wants= type dependency).
466 Note that these passive units cannot be started manually, i.e.
468 "systemctl start time-sync.target" will fail with an error. They can
469 only be pulled in by dependency. This is enforced since they exist for
470 ordering purposes only and thus are not useful as only unit within a
471 transaction.
472 cryptsetup-pre.target
474 This passive target unit may be pulled in by services that want to
475 run before any encrypted block device is set up. All encrypted
476 block devices are set up after this target has been reached. Since
477 the shutdown order is implicitly the reverse start-up order between
478 units, this target is particularly useful to ensure that a service
479 is shut down only after all encrypted block devices are fully
480 stopped.
481 getty-pre.target
483 A special passive target unit. Users of this target are expected to
484 pull it in the boot transaction via a dependency (e.g. Wants=).
485 Order your unit before this unit if you want to make use of the
486 console just before getty is started.
487 local-fs-pre.target
489 This target unit is automatically ordered before all local mount
490 points marked with auto (see above). It can be used to execute
491 certain units before all local mounts.
492 network.target
494 This unit is supposed to indicate when network functionality is
495 available, but it is only very weakly defined what that is supposed
496 to mean, with one exception: at shutdown, a unit that is ordered
497 after network.target will be stopped before the network — to
498 whatever level it might be set up then — is shut down. It is hence
499 useful when writing service files that require network access on
500 shutdown, which should order themselves after this target, but not
501 pull it in. Also see Running Services After the Network is up[1]
502 for more information. Also see network-online.target described
503 above.
504 network-pre.target
506 This passive target unit may be pulled in by services that want to
507 run before any network is set up, for example for the purpose of
508 setting up a firewall. All network management software orders
509 itself after this target, but does not pull it in.
510 nss-lookup.target
512 A target that should be used as synchronization point for all
513 host/network name service lookups. Note that this is independent of
514 UNIX user/group name lookups for which nss-user-lookup.target
515 should be used. All services for which the availability of full
516 host/network name resolution is essential should be ordered after
517 this target, but not pull it in. systemd automatically adds
518 dependencies of type After= for this target unit to all SysV init
519 script service units with an LSB header referring to the "$named"
520 facility.
521 nss-user-lookup.target
523 A target that should be used as synchronization point for all
524 regular UNIX user/group name service lookups. Note that this is
525 independent of host/network name lookups for which
526 nss-lookup.target should be used. All services for which the
527 availability of the full user/group database is essential should be
528 ordered after this target, but not pull it in. All services which
529 provide parts of the user/group database should be ordered before
530 this target, and pull it in. Note that this unit is only relevant
531 for regular users and groups — system users and groups are required
532 to be resolvable during earliest boot already, and hence do not
533 need any special ordering against this target.
534 remote-fs-pre.target
536 This target unit is automatically ordered before all mount point
537 units (see above) and cryptsetup devices marked with the _netdev.
538 It can be used to run certain units before remote encrypted devices
539 and mounts are established. Note that this unit is generally not
540 part of the initial transaction, unless the unit that wants to be
541 ordered before all remote mounts pulls it in via a Wants= type
542 dependency. If the unit wants to be pulled in by the first remote
543 mount showing up, it should use network-online.target (see above).
544 rpcbind.target
546 The portmapper/rpcbind pulls in this target and orders itself
547 before it, to indicate its availability. systemd automatically adds
548 dependencies of type After= for this target unit to all SysV init
549 script service units with an LSB header referring to the "$portmap"
550 facility.
551 time-sync.target
553 Services responsible for synchronizing the system clock from a
554 remote source (such as NTP client implementations) should pull in
555 this target and order themselves before it. All services where
556 correct time is essential should be ordered after this unit, but
557 not pull it in. systemd automatically adds dependencies of type
558 After= for this target unit to all SysV init script service units
559 with an LSB header referring to the "$time" facility.
560
562 When systemd runs as a user instance, the following special units are
563 available, which have similar definitions as their system counterparts:
564 exit.target, default.target, shutdown.target, sockets.target,
565 timers.target, paths.target, bluetooth.target, printer.target,
566 smartcard.target, sound.target.
567
569 graphical-session.target
570 This target is active whenever any graphical session is running. It
571 is used to stop user services which only apply to a graphical (X,
572 Wayland, etc.) session when the session is terminated. Such
573 services should have "PartOf=graphical-session.target" in their
574 "[Unit]" section. A target for a particular session (e. g.
575 gnome-session.target) starts and stops "graphical-session.target"
576 with "BindsTo=graphical-session.target".
577 Which services are started by a session target is determined by the
579 "Wants=" and "Requires=" dependencies. For services that can be
580 enabled independently, symlinks in ".wants/" and ".requires/"
581 should be used, see systemd.unit(5). Those symlinks should either
582 be shipped in packages, or should be added dynamically after
583 installation, for example using "systemctl add-wants", see
584 systemctl(1).
585 Example 1. Nautilus as part of a GNOME session
587 "gnome-session.target" pulls in Nautilus as top-level service:
588 [Unit]
590 Description=User systemd services for GNOME graphical session
591 Wants=nautilus.service
592 BindsTo=graphical-session.target
593 "nautilus.service" gets stopped when the session stops:
595 [Unit]
597 Description=Render the desktop icons with Nautilus
598 PartOf=graphical-session.target
599 [Service]
601 ...
602 graphical-session-pre.target
604 This target contains services which set up the environment or
605 global configuration of a graphical session, such as SSH/GPG agents
606 (which need to export an environment variable into all desktop
607 processes) or migration of obsolete d-conf keys after an OS upgrade
608 (which needs to happen before starting any process that might use
609 them). This target must be started before starting a graphical
610 session like gnome-session.target.
611
613 There are four ".slice" units which form the basis of the hierarchy for
614 assignment of resources for services, users, and virtual machines or
615 containers. See systemd.slice(7) for details about slice units.
616 -.slice
618 The root slice is the root of the slice hierarchy. It usually does
619 not contain units directly, but may be used to set defaults for the
620 whole tree.
621 system.slice
623 By default, all system services started by systemd are found in
624 this slice.
625 user.slice
627 By default, all user processes and services started on behalf of
628 the user, including the per-user systemd instance are found in this
629 slice. This is pulled in by systemd-logind.service
630 machine.slice
632 By default, all virtual machines and containers registered with
633 systemd-machined are found in this slice. This is pulled in by
634 systemd-machined.service
635
637 systemd(1), systemd.unit(5), systemd.service(5), systemd.socket(5),
638 systemd.target(5), systemd.slice(5), bootup(7), systemd-fstab-
639 generator(8), user@.service(5)
640
642 1. Running Services After the Network is up
643 https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget
644 2. Syslog Interface
646 https://www.freedesktop.org/wiki/Software/systemd/syslog
647systemd 239 SYSTEMD.SPECIAL(7)