NAME | SYNOPSIS | DESCRIPTION | SPECIAL SYSTEM UNITS | SPECIAL SYSTEM UNITS FOR DEVICES | SPECIAL PASSIVE SYSTEM UNITS | SPECIAL USER UNITS | SPECIAL PASSIVE USER UNITS | SPECIAL SLICE UNITS | SEE ALSO | NOTES | COLOPHON

SYSTEMD.SPECIAL(7)             systemd.special            SYSTEMD.SPECIAL(7)

NAME         top

       systemd.special - Special systemd units

SYNOPSIS         top

       basic.target, bluetooth.target, cryptsetup-pre.target,
       cryptsetup.target, ctrl-alt-del.target, default.target,
       emergency.target, exit.target, final.target, getty.target,
       graphical.target, halt.target, hibernate.target, hybrid-sleep.target,
       initrd-fs.target, initrd-root-device.target, initrd-root-fs.target,
       kbrequest.target, kexec.target, local-fs-pre.target, local-fs.target,
       machines.targetmulti-user.target, network-online.target,
       network-pre.target, network.target, nss-lookup.target,
       nss-user-lookup.target, paths.target, poweroff.target,
       printer.target, reboot.target, remote-fs-pre.target,
       remote-fs.target, rescue.target, rpcbind.target, runlevel2.target,
       runlevel3.target, runlevel4.target, runlevel5.target,
       shutdown.target, sigpwr.target, sleep.target, slices.target,
       smartcard.target, sockets.target, sound.target, suspend.target,
       swap.target, sysinit.target, syslog.socket, system-update.target,
       time-sync.target, timers.target, umount.target, -.slice,
       system.slice, user.slice, machine.slice, dbus.service, dbus.socket,
       display-manager.service, system-update-cleanup.service

DESCRIPTION         top

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

SPECIAL SYSTEM UNITS         top

       basic.target
           A special target unit covering basic boot-up.

           systemd automatically adds dependency of the type After= for this
           target unit to all services (except for those with
           DefaultDependencies=no).

           Usually, this should pull-in all local mount points plus /var,
           /tmp and /var/tmp, swap devices, sockets, timers, path units and
           other basic initialization necessary for general purpose daemons.
           The mentioned mount points are special cased to allow them to be
           remote.

           This target usually does not pull in any non-target units
           directly, but rather does so indirectly via other early boot
           targets. It is instead meant as a synchronization point for late
           boot services. Refer to bootup(7) for details on the targets
           involved.

       ctrl-alt-del.target
           systemd starts this target whenever Control+Alt+Del is pressed on
           the console. Usually, this should be aliased (symlinked) to
           reboot.target.

       cryptsetup.target
           A target that pulls in setup services for all encrypted block
           devices.

       dbus.service
           A special unit for the D-Bus bus daemon. As soon as this service
           is fully started up systemd will connect to it and register its
           service.

       dbus.socket
           A special unit for the D-Bus system bus socket. All units with
           Type=dbus automatically gain a dependency on this unit.

       default.target
           The default unit systemd starts at bootup. Usually, this should
           be aliased (symlinked) to multi-user.target or graphical.target.

           The default unit systemd starts at bootup can be overridden with
           the systemd.unit= kernel command line option.

       display-manager.service
           The display manager service. Usually, this should be aliased
           (symlinked) to gdm.service or a similar display manager service.

       emergency.target
           A special target unit that starts an emergency shell on the main
           console. This target does not pull in any services or mounts. It
           is the most minimal version of starting the system in order to
           acquire an interactive shell; the only processes running are
           usually just the system manager (PID 1) and the shell process.
           This unit is supposed to be used with the kernel command line
           option systemd.unit=; it is also used when a file system check on
           a required file system fails, and boot-up cannot continue.
           Compare with rescue.target, which serves a similar purpose, but
           also starts the most basic services and mounts all file systems.

           Use the "systemd.unit=emergency.target" kernel command line
           option to boot into this mode. A short alias for this kernel
           command line option is "emergency", for compatibility with SysV.

           In many ways booting into emergency.target is similar to the
           effect of booting with "init=/bin/sh" on the kernel command line,
           except that emergency mode provides you with the full system and
           service manager, and allows starting individual units in order to
           continue the boot process in steps.

       exit.target
           A special service unit for shutting down the system or user
           service manager. It is equivalent to poweroff.target on
           non-container systems, and also works in containers.

           systemd will start this unit when it receives a request to shut
           down over D-Bus or a SIGTERM or SIGINT signal when running as
           user service daemon.

           Normally, this (indirectly) pulls in shutdown.target, which in
           turn should be conflicted by all units that want to be scheduled
           for shutdown when the service manager starts to exit.

       final.target
           A special target unit that is used during the shutdown logic and
           may be used to pull in late services after all normal services
           are already terminated and all mounts unmounted.

       getty.target
           A special target unit that pulls in statically configured local
           TTY getty instances.

       graphical.target
           A special target unit for setting up a graphical login screen.
           This pulls in multi-user.target.

           Units that are needed for graphical logins shall add Wants=
           dependencies for their unit to this unit (or multi-user.target)
           during installation. This is best configured via
           WantedBy=graphical.target in the unit's "[Install]" section.

       hibernate.target
           A special target unit for hibernating the system. This pulls in
           sleep.target.

       hybrid-sleep.target
           A special target unit for hibernating and suspending the system
           at the same time. This pulls in sleep.target.

       halt.target
           A special target unit for shutting down and halting the system.
           Note that this target is distinct from poweroff.target in that it
           generally really just halts the system rather than powering it
           down.

           Applications wanting to halt the system should start this unit.

       initrd-fs.target
           systemd-fstab-generator(3) automatically adds dependencies of
           type Before= to sysroot-usr.mount and all mount points found in
           /etc/fstab that have x-initrd.mount and not have noauto mount
           options set.

       kbrequest.target
           systemd starts this target whenever Alt+ArrowUp is pressed on the
           console. This is a good candidate to be aliased (symlinked) to
           rescue.target.

       kexec.target
           A special target unit for shutting down and rebooting the system
           via kexec.

           Applications wanting to reboot the system with kexec should start
           this unit.

       local-fs.target
           systemd-fstab-generator(3) automatically adds dependencies of
           type Before= to all mount units that refer to local mount points
           for this target unit. In addition, it adds dependencies of type
           Wants= to this target unit for those mounts listed in /etc/fstab
           that have the auto mount option set.

       machines.target
           A standard target unit for starting all the containers and other
           virtual machines. See systemd-nspawn@.service for an example.

       multi-user.target
           A special target unit for setting up a multi-user system
           (non-graphical). This is pulled in by graphical.target.

           Units that are needed for a multi-user system shall add Wants=
           dependencies for their unit to this unit during installation.
           This is best configured via WantedBy=multi-user.target in the
           unit's "[Install]" section.

       network-online.target
           Units that strictly require a configured network connection
           should pull in network-online.target (via a Wants= type
           dependency) and order themselves after it. This target unit is
           intended to pull in a service that delays further execution until
           the network is sufficiently set up. What precisely this requires
           is left to the implementation of the network managing service.

           Note the distinction between this unit and network.target. This
           unit is an active unit (i.e. pulled in by the consumer rather
           than the provider of this functionality) and pulls in a service
           which possibly adds substantial delays to further execution. In
           contrast, network.target is a passive unit (i.e. pulled in by the
           provider of the functionality, rather than the consumer) that
           usually does not delay execution much. Usually, network.target is
           part of the boot of most systems, while network-online.target is
           not, except when at least one unit requires it. Also see Running
           Services After the Network is up[1] for more information.

           All mount units for remote network file systems automatically
           pull in this unit, and order themselves after it. Note that
           networking daemons that simply provide functionality to other
           hosts generally do not need to pull this in.

       paths.target
           A special target unit that sets up all path units (see
           systemd.path(5) for details) that shall be active after boot.

           It is recommended that path units installed by applications get
           pulled in via Wants= dependencies from this unit. This is best
           configured via a WantedBy=paths.target in the path unit's
           "[Install]" section.

       poweroff.target
           A special target unit for shutting down and powering off the
           system.

           Applications wanting to power off the system should start this
           unit.

           runlevel0.target is an alias for this target unit, for
           compatibility with SysV.

       reboot.target
           A special target unit for shutting down and rebooting the system.

           Applications wanting to reboot the system should start this unit.

           runlevel6.target is an alias for this target unit, for
           compatibility with SysV.

       remote-fs.target
           Similar to local-fs.target, but for remote mount points.

           systemd automatically adds dependencies of type After= for this
           target unit to all SysV init script service units with an LSB
           header referring to the "$remote_fs" facility.

       rescue.target
           A special target unit that pulls in the base system (including
           system mounts) and spawns a rescue shell. Isolate to this target
           in order to administer the system in single-user mode with all
           file systems mounted but with no services running, except for the
           most basic. Compare with emergency.target, which is much more
           reduced and does not provide the file systems or most basic
           services.

           runlevel1.target is an alias for this target unit, for
           compatibility with SysV.

           Use the "systemd.unit=rescue.target" kernel command line option
           to boot into this mode. A short alias for this kernel command
           line option is "1", for compatibility with SysV.

       initrd-root-device.target
           A special initrd target unit that is reached when the root
           filesystem device is available, but before it has been mounted.
           systemd-fstab-generator(3) and systemd-gpt-auto-generator(3)
           automatically setup the appropriate dependencies to make this
           happen.

       initrd-root-fs.target
           systemd-fstab-generator(3) automatically adds dependencies of
           type Before= to the sysroot.mount unit, which is generated from
           the kernel command line.

       runlevel2.target, runlevel3.target, runlevel4.target,
       runlevel5.target
           These are targets that are called whenever the SysV compatibility
           code asks for runlevel 2, 3, 4, 5, respectively. It is a good
           idea to make this an alias for (i.e. symlink to) graphical.target
           (for runlevel 5) or multi-user.target (the others).

       shutdown.target
           A special target unit that terminates the services on system
           shutdown.

           Services that shall be terminated on system shutdown shall add
           Conflicts= and Before= dependencies to this unit for their
           service unit, which is implicitly done when
           DefaultDependencies=yes is set (the default).

       sigpwr.target
           A special target that is started when systemd receives the SIGPWR
           process signal, which is normally sent by the kernel or UPS
           daemons when power fails.

       sleep.target
           A special target unit that is pulled in by suspend.target,
           hibernate.target and hybrid-sleep.target and may be used to hook
           units into the sleep state logic.

       slices.target
           A special target unit that sets up all slice units (see
           systemd.slice(5) for details) that shall be active after boot. By
           default the generic user.slice, system.slice, machines.slice
           slice units, as well as the root slice unit -.slice are pulled in
           and ordered before this unit (see below).

           It's a good idea to add WantedBy=slices.target lines to the
           "[Install]" section of all slices units that may be installed
           dynamically.

       sockets.target
           A special target unit that sets up all socket units (see
           systemd.socket(5) for details) that shall be active after boot.

           Services that can be socket-activated shall add Wants=
           dependencies to this unit for their socket unit during
           installation. This is best configured via a
           WantedBy=sockets.target in the socket unit's "[Install]" section.

       suspend.target
           A special target unit for suspending the system. This pulls in
           sleep.target.

       swap.target
           Similar to local-fs.target, but for swap partitions and swap
           files.

       sysinit.target
           systemd automatically adds dependencies of the types Requires=
           and After= for this target unit to all services (except for those
           with DefaultDependencies=no).

           This target pulls in the services required for system
           initialization. System services pulled in by this target should
           declare DefaultDependencies=no and specify all their dependencies
           manually, including access to anything more than a read only root
           filesystem. For details on the dependencies of this target, refer
           to bootup(7).

       syslog.socket
           The socket unit syslog implementations should listen on. All
           userspace log messages will be made available on this socket. For
           more information about syslog integration, please consult the
           Syslog Interface[2] document.

       system-update.target, system-update-cleanup.service
           A special target unit that is used for offline system updates.
           systemd-system-update-generator(8) will redirect the boot process
           to this target if /system-update exists. For more information see
           systemd.offline-updates(7).

           Updates should happen before the system-update.target is reached,
           and the services which implement them should cause the machine to
           reboot. As a safety measure, if this does not happen, and
           /system-update still exists after system-update.target is
           reached, system-update-cleanup.service will remove this symlink
           and reboot the machine.

       timers.target
           A special target unit that sets up all timer units (see
           systemd.timer(5) for details) that shall be active after boot.

           It is recommended that timer units installed by applications get
           pulled in via Wants= dependencies from this unit. This is best
           configured via WantedBy=timers.target in the timer unit's
           "[Install]" section.

       umount.target
           A special target unit that unmounts all mount and automount
           points on system shutdown.

           Mounts that shall be unmounted on system shutdown shall add
           Conflicts dependencies to this unit for their mount unit, which
           is implicitly done when DefaultDependencies=yes is set (the
           default).

SPECIAL SYSTEM UNITS FOR DEVICES         top

       Some target units are automatically pulled in as devices of certain
       kinds show up in the system. These may be used to automatically
       activate various services based on the specific type of the available
       hardware.

       bluetooth.target
           This target is started automatically as soon as a Bluetooth
           controller is plugged in or becomes available at boot.

           This may be used to pull in Bluetooth management daemons
           dynamically when Bluetooth hardware is found.

       printer.target
           This target is started automatically as soon as a printer is
           plugged in or becomes available at boot.

           This may be used to pull in printer management daemons
           dynamically when printer hardware is found.

       smartcard.target
           This target is started automatically as soon as a smartcard
           controller is plugged in or becomes available at boot.

           This may be used to pull in smartcard management daemons
           dynamically when smartcard hardware is found.

       sound.target
           This target is started automatically as soon as a sound card is
           plugged in or becomes available at boot.

           This may be used to pull in audio management daemons dynamically
           when audio hardware is found.

SPECIAL PASSIVE SYSTEM UNITS         top

       A number of special system targets are defined that can be used to
       properly order boot-up of optional services. These targets are
       generally not part of the initial boot transaction, unless they are
       explicitly pulled in by one of the implementing services. Note
       specifically that these passive target units are generally not pulled
       in by the consumer of a service, but by the provider of the service.
       This means: a consuming service should order itself after these
       targets (as appropriate), but not pull it in. A providing service
       should order itself before these targets (as appropriate) and pull it
       in (via a Wants= type dependency).

       Note that these passive units cannot be started manually, i.e.
       "systemctl start time-sync.target" will fail with an error. They can
       only be pulled in by dependency. This is enforced since they exist
       for ordering purposes only and thus are not useful as only unit
       within a transaction.

       cryptsetup-pre.target
           This passive target unit may be pulled in by services that want
           to run before any encrypted block device is set up. All encrypted
           block devices are set up after this target has been reached.
           Since the shutdown order is implicitly the reverse start-up order
           between units, this target is particularly useful to ensure that
           a service is shut down only after all encrypted block devices are
           fully stopped.

       local-fs-pre.target
           This target unit is automatically ordered before all local mount
           points marked with auto (see above). It can be used to execute
           certain units before all local mounts.

       network.target
           This unit is supposed to indicate when network functionality is
           available, but it is only very weakly defined what that is
           supposed to mean, with one exception: at shutdown, a unit that is
           ordered after network.target will be stopped before the network —
           to whatever level it might be set up then — is shut down. It is
           hence useful when writing service files that require network
           access on shutdown, which should order themselves after this
           target, but not pull it in. Also see Running Services After the
           Network is up[1] for more information. Also see
           network-online.target described above.

           systemd automatically adds dependencies of type After= for this
           target unit to all SysV init script service units with an LSB
           header referring to the "$network" facility.

       network-pre.target
           This passive target unit may be pulled in by services that want
           to run before any network is set up, for example for the purpose
           of setting up a firewall. All network management software orders
           itself after this target, but does not pull it in.

       nss-lookup.target
           A target that should be used as synchronization point for all
           host/network name service lookups. Note that this is independent
           of user/group name lookups for which nss-user-lookup.target
           should be used. All services for which the availability of full
           host/network name resolution is essential should be ordered after
           this target, but not pull it in. systemd automatically adds
           dependencies of type After= for this target unit to all SysV init
           script service units with an LSB header referring to the "$named"
           facility.

       nss-user-lookup.target
           A target that should be used as synchronization point for all
           user/group name service lookups. Note that this is independent of
           host/network name lookups for which nss-lookup.target should be
           used. All services for which the availability of the full
           user/group database is essential should be ordered after this
           target, but not pull it in. Note that system users are always
           resolvable, and hence do not require any special ordering against
           this target.

       remote-fs-pre.target
           This target unit is automatically ordered before all remote mount
           point units (see above). It can be used to run certain units
           before the remote mounts are established. Note that this unit is
           generally not part of the initial transaction, unless the unit
           that wants to be ordered before all remote mounts pulls it in via
           a Wants= type dependency. If the unit wants to be pulled in by
           the first remote mount showing up, it should use
           network-online.target (see above).

       rpcbind.target
           The portmapper/rpcbind pulls in this target and orders itself
           before it, to indicate its availability. systemd automatically
           adds dependencies of type After= for this target unit to all SysV
           init script service units with an LSB header referring to the
           "$portmap" facility.

       time-sync.target
           Services responsible for synchronizing the system clock from a
           remote source (such as NTP client implementations) should pull in
           this target and order themselves before it. All services where
           correct time is essential should be ordered after this unit, but
           not pull it in. systemd automatically adds dependencies of type
           After= for this target unit to all SysV init script service units
           with an LSB header referring to the "$time" facility.

SPECIAL USER UNITS         top

       When systemd runs as a user instance, the following special units are
       available, which have similar definitions as their system
       counterparts: exit.target, default.target, shutdown.target,
       sockets.target, timers.target, paths.target, bluetooth.target,
       printer.target, smartcard.target, sound.target.

SPECIAL PASSIVE USER UNITS         top

       graphical-session.target
           This target is active whenever any graphical session is running.
           It is used to stop user services which only apply to a graphical
           (X, Wayland, etc.) session when the session is terminated. Such
           services should have "PartOf=graphical-session.target" in their
           "[Unit]" section. A target for a particular session (e. g.
           gnome-session.target) starts and stops "graphical-session.target"
           with "BindsTo=graphical-session.target".

           Which services are started by a session target is determined by
           the "Wants=" and "Requires=" dependencies. For services that can
           be enabled independently, symlinks in ".wants/" and ".requires/"
           should be used, see systemd.unit(5). Those symlinks should either
           be shipped in packages, or should be added dynamically after
           installation, for example using "systemctl add-wants", see
           systemctl(1).

           Example 1. Nautilus as part of a GNOME session
           "gnome-session.target" pulls in Nautilus as top-level service:

               [Unit]
               Description=User systemd services for GNOME graphical session
               Wants=nautilus.service
               BindsTo=graphical-session.target

           "nautilus.service" gets stopped when the session stops:

               [Unit]
               Description=Render the desktop icons with Nautilus
               PartOf=graphical-session.target

               [Service]
               ...

       graphical-session-pre.target
           This target contains services which set up the environment or
           global configuration of a graphical session, such as SSH/GPG
           agents (which need to export an environment variable into all
           desktop processes) or migration of obsolete d-conf keys after an
           OS upgrade (which needs to happen before starting any process
           that might use them). This target must be started before starting
           a graphical session like gnome-session.target.

SPECIAL SLICE UNITS         top

       There are four ".slice" units which form the basis of the hierarchy
       for assignment of resources for services, users, and virtual machines
       or containers.

       -.slice
           The root slice is the root of the hierarchy. It usually does not
           contain units directly, but may be used to set defaults for the
           whole tree.

       system.slice
           By default, all system services started by systemd are found in
           this slice.

       user.slice
           By default, all user processes and services started on behalf of
           the user, including the per-user systemd instance are found in
           this slice.

       machine.slice
           By default, all virtual machines and containers registered with
           systemd-machined are found in this slice.

SEE ALSO         top

       systemd(1), systemd.unit(5), systemd.service(5), systemd.socket(5),
       systemd.target(5), systemd.slice(5), bootup(7),
       systemd-fstab-generator(8)

NOTES         top

        1. Running Services After the Network is up
           https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget

        2. Syslog Interface
           https://www.freedesktop.org/wiki/Software/systemd/syslog

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository 
       ⟨https://github.com/systemd/systemd.git⟩ on 2017-09-15.  If you dis‐
       cover any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 234                                               SYSTEMD.SPECIAL(7)

Pages that refer to this page: machinectl(1)systemctl(1)systemd(1)systemd.mount(5)systemd.resource-control(5)systemd.slice(5)systemd.target(5)systemd.unit(5)bootup(7)daemon(7)systemd.directives(7)systemd.index(7)lvm2-activation-generator(8)systemd-halt.service(8)systemd-machined.service(8)systemd-suspend.service(8)systemd-system-update-generator(8)