1SYSTEMD.SPECIAL(7)              systemd.special             SYSTEMD.SPECIAL(7)
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3
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NAME

6       systemd.special - Special systemd units
7

SYNOPSIS

9       basic.target, bluetooth.target, cryptsetup-pre.target,
10       cryptsetup.target, veritysetup-pre.target, veritysetup.target,
11       ctrl-alt-del.target, blockdev@.target, boot-complete.target,
12       default.target, emergency.target, exit.target, final.target,
13       first-boot-complete.target, getty.target, getty-pre.target,
14       graphical.target, halt.target, hibernate.target, hybrid-sleep.target,
15       suspend-then-hibernate.target, initrd.target, initrd-fs.target,
16       initrd-root-device.target, initrd-root-fs.target, kbrequest.target,
17       kexec.target, local-fs-pre.target, local-fs.target, machines.target
18       multi-user.target, network-online.target, network-pre.target,
19       network.target, nss-lookup.target, nss-user-lookup.target,
20       paths.target, poweroff.target, printer.target, reboot.target,
21       remote-cryptsetup.target, remote-veritysetup.target,
22       remote-fs-pre.target, remote-fs.target, rescue.target, rpcbind.target,
23       runlevel2.target, runlevel3.target, runlevel4.target, runlevel5.target,
24       shutdown.target, sigpwr.target, sleep.target, slices.target,
25       smartcard.target, sockets.target, sound.target, suspend.target,
26       swap.target, sysinit.target, system-update.target,
27       system-update-pre.target, time-set.target, time-sync.target,
28       timers.target, umount.target, usb-gadget.target, -.slice, system.slice,
29       user.slice, machine.slice, -.mount, dbus.service, dbus.socket,
30       display-manager.service, init.scope, syslog.socket,
31       system-update-cleanup.service
32

DESCRIPTION

34       A few units are treated specially by systemd. Many of them have special
35       internal semantics and cannot be renamed, while others simply have a
36       standard meaning and should be present on all systems.
37

UNITS MANAGED BY THE SYSTEM SERVICE MANAGER

39   Special System Units
40       -.mount
41           The root mount point, i.e. the mount unit for the / path. This unit
42           is unconditionally active, during the entire time the system is up,
43           as this mount point is where the basic userspace is running from.
44
45       basic.target
46           A special target unit covering basic boot-up.
47
48           systemd automatically adds dependency of the type After= for this
49           target unit to all services (except for those with
50           DefaultDependencies=no).
51
52           Usually, this should pull-in all local mount points plus /var/,
53           /tmp/ and /var/tmp/, swap devices, sockets, timers, path units and
54           other basic initialization necessary for general purpose daemons.
55           The mentioned mount points are special cased to allow them to be
56           remote.
57
58           This target usually does not pull in any non-target units directly,
59           but rather does so indirectly via other early boot targets. It is
60           instead meant as a synchronization point for late boot services.
61           Refer to bootup(7) for details on the targets involved.
62
63       boot-complete.target
64           This target is intended as generic synchronization point for
65           services that shall determine or act on whether the boot process
66           completed successfully. Order units that are required to succeed
67           for a boot process to be considered successful before this unit,
68           and add a Requires= dependency from the target unit to them. Order
69           units that shall only run when the boot process is considered
70           successful after the target unit and pull in the target from it,
71           also with Requires=. Note that by default this target unit is not
72           part of the initial boot transaction, but is supposed to be pulled
73           in only if required by units that want to run only on successful
74           boots.
75
76           See systemd-boot-check-no-failures.service(8) for a service that
77           implements a generic system health check and orders itself before
78           boot-complete.target.
79
80           See systemd-bless-boot.service(8) for a service that propagates
81           boot success information to the boot loader, and orders itself
82           after boot-complete.target.
83
84       ctrl-alt-del.target
85           systemd starts this target whenever Control+Alt+Del is pressed on
86           the console. Usually, this should be aliased (symlinked) to
87           reboot.target.
88
89       cryptsetup.target
90           A target that pulls in setup services for all encrypted block
91           devices.
92
93       veritysetup.target
94           A target that pulls in setup services for all verity integrity
95           protected block devices.
96
97       dbus.service
98           A special unit for the D-Bus bus daemon. As soon as this service is
99           fully started up systemd will connect to it and register its
100           service.
101
102       dbus.socket
103           A special unit for the D-Bus system bus socket. All units with
104           Type=dbus automatically gain a dependency on this unit.
105
106       default.target
107           The default unit systemd starts at bootup. Usually, this should be
108           aliased (symlinked) to multi-user.target or graphical.target. See
109           bootup(7) for more discussion.
110
111           The default unit systemd starts at bootup can be overridden with
112           the systemd.unit= kernel command line option, or more conveniently,
113           with the short names like single, rescue, 1, 3, 5, ...; see
114           systemd(1).
115
116       display-manager.service
117           The display manager service. Usually, this should be aliased
118           (symlinked) to gdm.service or a similar display manager service.
119
120       emergency.target
121           A special target unit that starts an emergency shell on the main
122           console. This target does not pull in other services or mounts. It
123           is the most minimal version of starting the system in order to
124           acquire an interactive shell; the only processes running are
125           usually just the system manager (PID 1) and the shell process. This
126           unit may be used by specifying emergency on the kernel command
127           line; it is also used when a file system check on a required file
128           system fails and boot-up cannot continue. Compare with
129           rescue.target, which serves a similar purpose, but also starts the
130           most basic services and mounts all file systems.
131
132           In many ways booting into emergency.target is similar to the effect
133           of booting with "init=/bin/sh" on the kernel command line, except
134           that emergency mode provides you with the full system and service
135           manager, and allows starting individual units in order to continue
136           the boot process in steps.
137
138           Note that depending on how emergency.target is reached, the root
139           file system might be mounted read-only or read-write (no remounting
140           is done specially for this target). For example, the system may
141           boot with root mounted read-only when ro is used on the kernel
142           command line and remain this way for emergency.target, or the
143           system may transition to emergency.target after the system has been
144           partially booted and disks have already been remounted read-write.
145
146       exit.target
147           A special service unit for shutting down the system or user service
148           manager. It is equivalent to poweroff.target on non-container
149           systems, and also works in containers.
150
151           systemd will start this unit when it receives the SIGTERM or SIGINT
152           signal when running as user service daemon.
153
154           Normally, this (indirectly) pulls in shutdown.target, which in turn
155           should be conflicted by all units that want to be scheduled for
156           shutdown when the service manager starts to exit.
157
158       final.target
159           A special target unit that is used during the shutdown logic and
160           may be used to pull in late services after all normal services are
161           already terminated and all mounts unmounted.
162
163       getty.target
164           A special target unit that pulls in statically configured local TTY
165           getty instances.
166
167       graphical.target
168           A special target unit for setting up a graphical login screen. This
169           pulls in multi-user.target.
170
171           Units that are needed for graphical logins shall add Wants=
172           dependencies for their unit to this unit (or multi-user.target)
173           during installation. This is best configured via
174           WantedBy=graphical.target in the unit's [Install] section.
175
176       hibernate.target
177           A special target unit for hibernating the system. This pulls in
178           sleep.target.
179
180       hybrid-sleep.target
181           A special target unit for hibernating and suspending the system at
182           the same time. This pulls in sleep.target.
183
184       suspend-then-hibernate.target
185           A special target unit for suspending the system for a period of
186           time, waking it and putting it into hibernate. This pulls in
187           sleep.target.
188
189       halt.target
190           A special target unit for shutting down and halting the system.
191           Note that this target is distinct from poweroff.target in that it
192           generally really just halts the system rather than powering it
193           down.
194
195           Applications wanting to halt the system should not start this unit
196           directly, but should instead execute systemctl halt (possibly with
197           the --no-block option) or call systemd(1)'s
198           org.freedesktop.systemd1.Manager.Halt D-Bus method directly.
199
200       init.scope
201           This scope unit is where the system and service manager (PID 1)
202           itself resides. It is active as long as the system is running.
203
204       initrd.target
205           This is the default target in the initramfs, similar to
206           default.target in the main system. It is used to mount the real
207           root and transition to it. See bootup(7) for more discussion.
208
209       initrd-fs.target
210           systemd-fstab-generator(3) automatically adds dependencies of type
211           Before= to sysroot-usr.mount and all mount points found in
212           /etc/fstab that have x-initrd.mount and not have noauto mount
213           options set.
214
215       initrd-root-device.target
216           A special initrd target unit that is reached when the root
217           filesystem device is available, but before it has been mounted.
218           systemd-fstab-generator(3) and systemd-gpt-auto-generator(3)
219           automatically setup the appropriate dependencies to make this
220           happen.
221
222       initrd-root-fs.target
223           systemd-fstab-generator(3) automatically adds dependencies of type
224           Before= to the sysroot.mount unit, which is generated from the
225           kernel command line.
226
227       kbrequest.target
228           systemd starts this target whenever Alt+ArrowUp is pressed on the
229           console. Note that any user with physical access to the machine
230           will be able to do this, without authentication, so this should be
231           used carefully.
232
233       kexec.target
234           A special target unit for shutting down and rebooting the system
235           via kexec.
236
237           Applications wanting to reboot the system should not start this
238           unit directly, but should instead execute systemctl kexec (possibly
239           with the --no-block option) or call systemd(1)'s
240           org.freedesktop.systemd1.Manager.KExec D-Bus method directly.
241
242       local-fs.target
243           systemd-fstab-generator(3) automatically adds dependencies of type
244           Before= to all mount units that refer to local mount points for
245           this target unit. In addition, it adds dependencies of type Wants=
246           to this target unit for those mounts listed in /etc/fstab that have
247           the auto mount option set.
248
249       machines.target
250           A standard target unit for starting all the containers and other
251           virtual machines. See systemd-nspawn@.service for an example.
252
253       multi-user.target
254           A special target unit for setting up a multi-user system
255           (non-graphical). This is pulled in by graphical.target.
256
257           Units that are needed for a multi-user system shall add Wants=
258           dependencies for their unit to this unit during installation. This
259           is best configured via WantedBy=multi-user.target in the unit's
260           [Install] section.
261
262       network-online.target
263           Units that strictly require a configured network connection should
264           pull in network-online.target (via a Wants= type dependency) and
265           order themselves after it. This target unit is intended to pull in
266           a service that delays further execution until the network is
267           sufficiently set up. What precisely this requires is left to the
268           implementation of the network managing service.
269
270           Note the distinction between this unit and network.target. This
271           unit is an active unit (i.e. pulled in by the consumer rather than
272           the provider of this functionality) and pulls in a service which
273           possibly adds substantial delays to further execution. In contrast,
274           network.target is a passive unit (i.e. pulled in by the provider of
275           the functionality, rather than the consumer) that usually does not
276           delay execution much. Usually, network.target is part of the boot
277           of most systems, while network-online.target is not, except when at
278           least one unit requires it. Also see Running Services After the
279           Network is up[1] for more information.
280
281           All mount units for remote network file systems automatically pull
282           in this unit, and order themselves after it. Note that networking
283           daemons that simply provide functionality to other hosts (as
284           opposed to consume functionality of other hosts) generally do not
285           need to pull this in.
286
287           systemd automatically adds dependencies of type Wants= and After=
288           for this target unit to all SysV init script service units with an
289           LSB header referring to the "$network" facility.
290
291           Note that this unit is only useful during the original system
292           start-up logic. After the system has completed booting up, it will
293           not track the online state of the system anymore. Due to this it
294           cannot be used as a network connection monitor concept, it is
295           purely a one-time system start-up concept.
296
297       paths.target
298           A special target unit that sets up all path units (see
299           systemd.path(5) for details) that shall be active after boot.
300
301           It is recommended that path units installed by applications get
302           pulled in via Wants= dependencies from this unit. This is best
303           configured via a WantedBy=paths.target in the path unit's [Install]
304           section.
305
306       poweroff.target
307           A special target unit for shutting down and powering off the
308           system.
309
310           Applications wanting to power off the system should not start this
311           unit directly, but should instead execute systemctl poweroff
312           (possibly with the --no-block option) or call systemd-logind(8)'s
313           org.freedesktop.login1.Manager.PowerOff D-Bus method directly.
314
315           runlevel0.target is an alias for this target unit, for
316           compatibility with SysV.
317
318       reboot.target
319           A special target unit for shutting down and rebooting the system.
320
321           Applications wanting to reboot the system should not start this
322           unit directly, but should instead execute systemctl reboot
323           (possibly with the --no-block option) or call systemd-logind(8)'s
324           org.freedesktop.login1.Manager.Reboot D-Bus method directly.
325
326           runlevel6.target is an alias for this target unit, for
327           compatibility with SysV.
328
329       remote-cryptsetup.target
330           Similar to cryptsetup.target, but for encrypted devices which are
331           accessed over the network. It is used for crypttab(8) entries
332           marked with _netdev.
333
334       remote-veritysetup.target
335           Similar to veritysetup.target, but for verity integrity protected
336           devices which are accessed over the network. It is used for
337           veritytab(8) entries marked with _netdev.
338
339       remote-fs.target
340           Similar to local-fs.target, but for remote mount points.
341
342           systemd automatically adds dependencies of type After= for this
343           target unit to all SysV init script service units with an LSB
344           header referring to the "$remote_fs" facility.
345
346       rescue.target
347           A special target unit that pulls in the base system (including
348           system mounts) and spawns a rescue shell. Isolate to this target in
349           order to administer the system in single-user mode with all file
350           systems mounted but with no services running, except for the most
351           basic. Compare with emergency.target, which is much more reduced
352           and does not provide the file systems or most basic services.
353           Compare with multi-user.target, this target could be seen as
354           single-user.target.
355
356           runlevel1.target is an alias for this target unit, for
357           compatibility with SysV.
358
359           Use the "systemd.unit=rescue.target" kernel command line option to
360           boot into this mode. A short alias for this kernel command line
361           option is "1", for compatibility with SysV.
362
363       runlevel2.target, runlevel3.target, runlevel4.target, runlevel5.target
364           These are targets that are called whenever the SysV compatibility
365           code asks for runlevel 2, 3, 4, 5, respectively. It is a good idea
366           to make this an alias for (i.e. symlink to) graphical.target (for
367           runlevel 5) or multi-user.target (the others).
368
369       shutdown.target
370           A special target unit that terminates the services on system
371           shutdown.
372
373           Services that shall be terminated on system shutdown shall add
374           Conflicts= and Before= dependencies to this unit for their service
375           unit, which is implicitly done when DefaultDependencies=yes is set
376           (the default).
377
378       sigpwr.target
379           A special target that is started when systemd receives the SIGPWR
380           process signal, which is normally sent by the kernel or UPS daemons
381           when power fails.
382
383       sleep.target
384           A special target unit that is pulled in by suspend.target,
385           hibernate.target and hybrid-sleep.target and may be used to hook
386           units into the sleep state logic.
387
388       slices.target
389           A special target unit that sets up all slice units (see
390           systemd.slice(5) for details) that shall always be active after
391           boot. By default the generic system.slice slice unit as well as the
392           root slice unit -.slice are pulled in and ordered before this unit
393           (see below).
394
395           Adding slice units to slices.target is generally not necessary.
396           Instead, when some unit that uses Slice= is started, the specified
397           slice will be started automatically. Adding WantedBy=slices.target
398           lines to the [Install] section should only be done for units that
399           need to be always active. In that case care needs to be taken to
400           avoid creating a loop through the automatic dependencies on
401           "parent" slices.
402
403       sockets.target
404           A special target unit that sets up all socket units (see
405           systemd.socket(5) for details) that shall be active after boot.
406
407           Services that can be socket-activated shall add Wants= dependencies
408           to this unit for their socket unit during installation. This is
409           best configured via a WantedBy=sockets.target in the socket unit's
410           [Install] section.
411
412       suspend.target
413           A special target unit for suspending the system. This pulls in
414           sleep.target.
415
416       swap.target
417           Similar to local-fs.target, but for swap partitions and swap files.
418
419       sysinit.target
420           systemd automatically adds dependencies of the types Requires= and
421           After= for this target unit to all services (except for those with
422           DefaultDependencies=no).
423
424           This target pulls in the services required for system
425           initialization. System services pulled in by this target should
426           declare DefaultDependencies=no and specify all their dependencies
427           manually, including access to anything more than a read only root
428           filesystem. For details on the dependencies of this target, refer
429           to bootup(7).
430
431       syslog.socket
432           The socket unit syslog implementations should listen on. All
433           userspace log messages will be made available on this socket. For
434           more information about syslog integration, please consult the
435           Syslog Interface[2] document.
436
437       system-update.target, system-update-pre.target,
438       system-update-cleanup.service
439           A special target unit that is used for offline system updates.
440           systemd-system-update-generator(8) will redirect the boot process
441           to this target if /system-update exists. For more information see
442           systemd.offline-updates(7).
443
444           Updates should happen before the system-update.target is reached,
445           and the services which implement them should cause the machine to
446           reboot. The main units executing the update should order themselves
447           after system-update-pre.target but not pull it in. Services which
448           want to run during system updates only, but before the actual
449           system update is executed should order themselves before this unit
450           and pull it in. As a safety measure, if this does not happen, and
451           /system-update still exists after system-update.target is reached,
452           system-update-cleanup.service will remove this symlink and reboot
453           the machine.
454
455       timers.target
456           A special target unit that sets up all timer units (see
457           systemd.timer(5) for details) that shall be active after boot.
458
459           It is recommended that timer units installed by applications get
460           pulled in via Wants= dependencies from this unit. This is best
461           configured via WantedBy=timers.target in the timer unit's [Install]
462           section.
463
464       umount.target
465           A special target unit that unmounts all mount and automount points
466           on system shutdown.
467
468           Mounts that shall be unmounted on system shutdown shall add
469           Conflicts dependencies to this unit for their mount unit, which is
470           implicitly done when DefaultDependencies=yes is set (the default).
471
472   Special System Units for Devices
473       Some target units are automatically pulled in as devices of certain
474       kinds show up in the system. These may be used to automatically
475       activate various services based on the specific type of the available
476       hardware.
477
478       bluetooth.target
479           This target is started automatically as soon as a Bluetooth
480           controller is plugged in or becomes available at boot.
481
482           This may be used to pull in Bluetooth management daemons
483           dynamically when Bluetooth hardware is found.
484
485       printer.target
486           This target is started automatically as soon as a printer is
487           plugged in or becomes available at boot.
488
489           This may be used to pull in printer management daemons dynamically
490           when printer hardware is found.
491
492       smartcard.target
493           This target is started automatically as soon as a smartcard
494           controller is plugged in or becomes available at boot.
495
496           This may be used to pull in smartcard management daemons
497           dynamically when smartcard hardware is found.
498
499       sound.target
500           This target is started automatically as soon as a sound card is
501           plugged in or becomes available at boot.
502
503           This may be used to pull in audio management daemons dynamically
504           when audio hardware is found.
505
506       usb-gadget.target
507           This target is started automatically as soon as a USB Device
508           Controller becomes available at boot.
509
510           This may be used to pull in usb gadget dynamically when UDC
511           hardware is found.
512
513   Special Passive System Units
514       A number of special system targets are defined that can be used to
515       properly order boot-up of optional services. These targets are
516       generally not part of the initial boot transaction, unless they are
517       explicitly pulled in by one of the implementing services. Note
518       specifically that these passive target units are generally not pulled
519       in by the consumer of a service, but by the provider of the service.
520       This means: a consuming service should order itself after these targets
521       (as appropriate), but not pull it in. A providing service should order
522       itself before these targets (as appropriate) and pull it in (via a
523       Wants= type dependency).
524
525       Note that these passive units cannot be started manually, i.e.
526       "systemctl start time-sync.target" will fail with an error. They can
527       only be pulled in by dependency. This is enforced since they exist for
528       ordering purposes only and thus are not useful as only unit within a
529       transaction.
530
531       blockdev@.target
532           This template unit is used to order mount units and other consumers
533           of block devices after services that synthesize these block
534           devices. In particular, this is intended to be used with storage
535           services (such as systemd-cryptsetup@.service(5)/ systemd-
536           veritysetup@.service(5)) that allocate and manage a virtual block
537           device. Storage services are ordered before an instance of
538           blockdev@.target, and the consumer units after it. The ordering is
539           particularly relevant during shutdown, as it ensures that the mount
540           is deactivated first and the service backing the mount later. The
541           blockdev@.target instance should be pulled in via a Wants=
542           dependency of the storage daemon and thus generally not be part of
543           any transaction unless a storage daemon is used. The instance name
544           for instances of this template unit must be a properly escaped
545           block device node path, e.g.  blockdev@dev-mapper-foobar.target for
546           the storage device /dev/mapper/foobar.
547
548       cryptsetup-pre.target
549           This passive target unit may be pulled in by services that want to
550           run before any encrypted block device is set up. All encrypted
551           block devices are set up after this target has been reached. Since
552           the shutdown order is implicitly the reverse start-up order between
553           units, this target is particularly useful to ensure that a service
554           is shut down only after all encrypted block devices are fully
555           stopped.
556
557       veritysetup-pre.target
558           This passive target unit may be pulled in by services that want to
559           run before any verity integrity protected block device is set up.
560           All verity integrity protected block devices are set up after this
561           target has been reached. Since the shutdown order is implicitly the
562           reverse start-up order between units, this target is particularly
563           useful to ensure that a service is shut down only after all verity
564           integrity protected block devices are fully stopped.
565
566       first-boot-complete.target
567           This passive target is intended as a synchronization point for
568           units that need to run once during the first boot. Only after all
569           units ordered before this target have finished, will the machine-
570           id(5) be committed to disk, marking the first boot as completed. If
571           the boot is aborted at any time before that, the next boot will
572           re-run any units with ConditionFirstBoot=yes.
573
574       getty-pre.target
575           A special passive target unit. Users of this target are expected to
576           pull it in the boot transaction via a dependency (e.g.  Wants=).
577           Order your unit before this unit if you want to make use of the
578           console just before getty is started.
579
580       local-fs-pre.target
581           This target unit is automatically ordered before all local mount
582           points marked with auto (see above). It can be used to execute
583           certain units before all local mounts.
584
585       network.target
586           This unit is supposed to indicate when network functionality is
587           available, but it is only very weakly defined what that is supposed
588           to mean. However, the following should apply at minimum:
589
590           •   At start-up, any configured synthetic network devices (i.e. not
591               physical ones that require hardware to show up and be probed,
592               but virtual ones like bridge devices and similar which are
593               created programmatically) that do not depend on any underlying
594               hardware should be allocated by the time this target is
595               reached. It is not necessary for these interfaces to also have
596               completed IP level configuration by the time network.target is
597               reached.
598
599           •   At shutdown, a unit that is ordered after network.target will
600               be stopped before the network — to whatever level it might be
601               set up by then — is shut down. It is hence useful when writing
602               service files that require network access on shutdown, which
603               should order themselves after this target, but not pull it in.
604               Also see Running Services After the Network is up[1] for more
605               information.
606
607           It must emphasized that at start-up there's no guarantee that
608           hardware-based devices have shown up by the time this target is
609           reached, or even acquired complete IP configuration. For that
610           purpose use network-online.target as described above.
611
612       network-pre.target
613           This passive target unit may be pulled in by services that want to
614           run before any network is set up, for example for the purpose of
615           setting up a firewall. All network management software orders
616           itself after this target, but does not pull it in.
617
618       nss-lookup.target
619           A target that should be used as synchronization point for all
620           host/network name service lookups. Note that this is independent of
621           UNIX user/group name lookups for which nss-user-lookup.target
622           should be used. All services for which the availability of full
623           host/network name resolution is essential should be ordered after
624           this target, but not pull it in. systemd automatically adds
625           dependencies of type After= for this target unit to all SysV init
626           script service units with an LSB header referring to the "$named"
627           facility.
628
629       nss-user-lookup.target
630           A target that should be used as synchronization point for all
631           regular UNIX user/group name service lookups. Note that this is
632           independent of host/network name lookups for which
633           nss-lookup.target should be used. All services for which the
634           availability of the full user/group database is essential should be
635           ordered after this target, but not pull it in. All services which
636           provide parts of the user/group database should be ordered before
637           this target, and pull it in. Note that this unit is only relevant
638           for regular users and groups — system users and groups are required
639           to be resolvable during earliest boot already, and hence do not
640           need any special ordering against this target.
641
642       remote-fs-pre.target
643           This target unit is automatically ordered before all mount point
644           units (see above) and cryptsetup/veritysetup devices marked with
645           the _netdev. It can be used to run certain units before remote
646           encrypted devices and mounts are established. Note that this unit
647           is generally not part of the initial transaction, unless the unit
648           that wants to be ordered before all remote mounts pulls it in via a
649           Wants= type dependency. If the unit wants to be pulled in by the
650           first remote mount showing up, it should use network-online.target
651           (see above).
652
653       rpcbind.target
654           The portmapper/rpcbind pulls in this target and orders itself
655           before it, to indicate its availability. systemd automatically adds
656           dependencies of type After= for this target unit to all SysV init
657           script service units with an LSB header referring to the "$portmap"
658           facility.
659
660       time-set.target
661           Services responsible for setting the system clock (CLOCK_REALTIME)
662           from a local source (such as a maintained timestamp file or
663           imprecise real-time clock) should pull in this target and order
664           themselves before it. Services where approximate, roughly monotonic
665           time is desired should be ordered after this unit, but not pull it
666           in.
667
668           This target does not provide the accuracy guarantees of
669           time-sync.target (see below), however does not depend on remote
670           clock sources to be reachable, i.e. the target is typically not
671           delayed by network problems and similar. Use of this target is
672           recommended for services where approximate clock accuracy and rough
673           monotonicity is desired but activation shall not be delayed for
674           possibly unreliable network communication.
675
676           The service manager automatically adds dependencies of type After=
677           for this target unit to all timer units with at least one
678           OnCalendar= directive.
679
680           The systemd-timesyncd.service(8) service is a simple daemon that
681           pulls in this target and orders itself before it. Besides
682           implementing the SNTP network protocol it maintains a timestamp
683           file on disk whose modification time is regularlary updated. At
684           service start-up the local system clock is set from that
685           modification time, ensuring it increases roughly monotonically.
686
687           Note that ordering a unit after time-set.target only has effect if
688           there's actually a service ordered before it that delays it until
689           the clock is adjusted for rough monotonicity. Otherwise, this
690           target might get reached before the clock is adjusted to be roughly
691           monotonic. Enable systemd-timesyncd.service(8), or an alternative
692           NTP implementation to delay the target.
693
694       time-sync.target
695           Services indicating completed synchronization of the system clock
696           (CLOCK_REALTIME) to a remote source should pull in this target and
697           order themselves before it. Services where accurate time is
698           essential should be ordered after this unit, but not pull it in.
699
700           The service manager automatically adds dependencies of type After=
701           for this target unit to all SysV init script service units with an
702           LSB header referring to the "$time" facility, as well to all timer
703           units with at least one OnCalendar= directive.
704
705           This target provides stricter clock accuracy guarantees than
706           time-set.target (see above), but likely requires network
707           communication and thus introduces unpredictable delays. Services
708           that require clock accuracy and where network communication delays
709           are acceptable should use this target. Services that require a less
710           accurate clock, and only approximate and roughly monotonic clock
711           behaviour should use time-set.target instead.
712
713           Note that ordering a unit after time-sync.target only has effect if
714           there's actually a service ordered before it that delays it until
715           clock synchronization is reached. Otherwise, this target might get
716           reached before the clock is synchronized to any remote accurate
717           reference clock. When using systemd-timesyncd.service(8), enable
718           systemd-time-wait-sync.service(8) to delay the target; or use an
719           equivalent service for other NTP implementations.
720
721           Table 1. Comparison
722           ┌───────────────────────────┬────────────────────────────────┐
723time-set.target            time-sync.target               
724           ├───────────────────────────┼────────────────────────────────┤
725           │"quick" to reach           │ "slow" to reach                │
726           ├───────────────────────────┼────────────────────────────────┤
727           │typically uses local clock │ typically uses remote          │
728           │sources, boot process not  │ clock sources, inserts         │
729           │affected by availability   │ dependencies on remote         │
730           │of external resources      │ resources into boot            │
731           │                           │ process                        │
732           ├───────────────────────────┼────────────────────────────────┤
733           │reliable, because local    │ unreliable, because            │
734           │                           │ typically network involved     │
735           ├───────────────────────────┼────────────────────────────────┤
736           │typically guarantees an    │ typically guarantees an        │
737           │approximate and roughly    │ accurate clock                 │
738           │monotonic clock only       │                                │
739           ├───────────────────────────┼────────────────────────────────┤
740           │implemented by             │ implemented by                 │
741           │systemd-timesyncd.service  │ systemd-time-wait-sync.service │
742           └───────────────────────────┴────────────────────────────────┘
743
744   Special Slice Units
745       There are four ".slice" units which form the basis of the hierarchy for
746       assignment of resources for services, users, and virtual machines or
747       containers. See systemd.slice(7) for details about slice units.
748
749       -.slice
750           The root slice is the root of the slice hierarchy. It usually does
751           not contain units directly, but may be used to set defaults for the
752           whole tree.
753
754       system.slice
755           By default, all system services started by systemd are found in
756           this slice.
757
758       user.slice
759           By default, all user processes and services started on behalf of
760           the user, including the per-user systemd instance are found in this
761           slice. This is pulled in by systemd-logind.service.
762
763       machine.slice
764           By default, all virtual machines and containers registered with
765           systemd-machined are found in this slice. This is pulled in by
766           systemd-machined.service.
767

UNITS MANAGED BY THE USER SERVICE MANAGER

769   Special User Units
770       When systemd runs as a user instance, the following special units are
771       available:
772
773       default.target
774           This is the main target of the user session, started by default.
775           Various services that compose the normal user session should be
776           pulled into this target. In this regard, default.target is similar
777           to multi-user.target in the system instance, but it is a real unit,
778           not an alias.
779
780       In addition, the following units are available which have definitions
781       similar to their system counterparts: exit.target, shutdown.target,
782       sockets.target, timers.target, paths.target, bluetooth.target,
783       printer.target, smartcard.target, sound.target.
784
785   Special Passive User Units
786       graphical-session.target
787           This target is active whenever any graphical session is running. It
788           is used to stop user services which only apply to a graphical (X,
789           Wayland, etc.) session when the session is terminated. Such
790           services should have "PartOf=graphical-session.target" in their
791           [Unit] section. A target for a particular session (e. g.
792           gnome-session.target) starts and stops "graphical-session.target"
793           with "BindsTo=graphical-session.target".
794
795           Which services are started by a session target is determined by the
796           "Wants=" and "Requires=" dependencies. For services that can be
797           enabled independently, symlinks in ".wants/" and ".requires/"
798           should be used, see systemd.unit(5). Those symlinks should either
799           be shipped in packages, or should be added dynamically after
800           installation, for example using "systemctl add-wants", see
801           systemctl(1).
802
803           Example 1. Nautilus as part of a GNOME session
804           "gnome-session.target" pulls in Nautilus as top-level service:
805
806               [Unit]
807               Description=User systemd services for GNOME graphical session
808               Wants=nautilus.service
809               BindsTo=graphical-session.target
810
811           "nautilus.service" gets stopped when the session stops:
812
813               [Unit]
814               Description=Render the desktop icons with Nautilus
815               PartOf=graphical-session.target
816
817               [Service]
818               ...
819
820       graphical-session-pre.target
821           This target contains services which set up the environment or
822           global configuration of a graphical session, such as SSH/GPG agents
823           (which need to export an environment variable into all desktop
824           processes) or migration of obsolete d-conf keys after an OS upgrade
825           (which needs to happen before starting any process that might use
826           them). This target must be started before starting a graphical
827           session like gnome-session.target.
828
829       xdg-desktop-autostart.target
830           The XDG specification defines a way to autostart applications using
831           XDG desktop files. systemd ships systemd-xdg-autostart-generator(8)
832           for the XDG desktop files in autostart directories. Desktop
833           Environments can opt-in to use this service by adding a Wants=
834           dependency on xdg-desktop-autostart.target.
835
836   Special User Slice Units
837       There are four ".slice" units which form the basis of the user
838       hierarchy for assignment of resources for user applications and
839       services. See systemd.slice(7) for details about slice units and the
840       documentation about Desktop Environments[3] for further information.
841
842       -.slice
843           The root slice is the root of the user's slice hierarchy. It
844           usually does not contain units directly, but may be used to set
845           defaults for the whole tree.
846
847       app.slice
848           By default, all user services and applications managed by systemd
849           are found in this slice. All interactively launched applications
850           like web browsers and text editors as well as non-critical services
851           should be placed into this slice.
852
853       session.slice
854           All essential services and applications required for the session
855           should use this slice. These are services that either cannot be
856           restarted easily or where latency issues may affect the
857           interactivity of the system and applications. This includes the
858           display server, screen readers and other services such as DBus or
859           XDG portals. Such services should be configured to be part of this
860           slice by adding Slice=session.slice to their unit files.
861
862       background.slice
863           All services running low-priority background tasks should use this
864           slice. This permits resources to be preferentially assigned to the
865           other slices. Examples include non-interactive tasks like file
866           indexing or backup operations where latency is not important.
867

SEE ALSO

869       systemd(1), systemd.unit(5), systemd.service(5), systemd.socket(5),
870       systemd.target(5), systemd.slice(5), bootup(7), systemd-fstab-
871       generator(8), user@.service(5)
872

NOTES

874        1. Running Services After the Network is up
875           https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget
876
877        2. Syslog Interface
878           https://www.freedesktop.org/wiki/Software/systemd/syslog
879
880        3. Desktop Environments
881           https://systemd.io/DESKTOP_ENVIRONMENTS
882
883
884
885systemd 248                                                 SYSTEMD.SPECIAL(7)
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