NAME

       systemd.special - Special systemd units

SYNOPSIS

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

DESCRIPTION

       A few units are treated specially by systemd. They have special internal semantics and cannot be renamed.

SPECIAL SYSTEM UNITS

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

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

           Usually this should pull-in all mount points, swap devices, sockets, timers, and path units and other
           basic initialization necessary for general purpose daemons.

       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 unit is supposed to be
           used with the kernel command line option systemd.unit= and has otherwise little use.

       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 fround in /etc/fstab that have the auto and x-initrd.mount 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.

           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 $local_fs facility.

       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.

       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-uer.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
           don't 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 for setting up the base system and a rescue shell.

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

       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) multi-user.target (for
           runlevel 2) or graphical.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= 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.

       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
           A special target unit covering early boot-up scripts.

       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.

       syslog.target
           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 $syslog facility.

       system-update.target
           A special target unit that is used for off-line system updates.  systemd-system-update-generator(8)
           will redirect the boot process to this target if /system-update exists. For more information see the
           System Updates Specification[3].

       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 umounts 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

       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

       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.

       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. 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.

       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.
           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.

       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).

           Again, this target unit is not suitable for pulling in other units, it is only useful for ordering.

       rpcbind.target
           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
           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

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

       In addition the following special unit is understood only when systemd runs as service instance:

       exit.target
           A special service unit for shutting down the user service manager.

           Applications wanting to terminate the user service manager should start this unit. If systemd
           receives SIGTERM or SIGINT when running as user service daemon it will start this unit.

           Normally, this pulls in shutdown.target which in turn should be conflicted by all units that want to
           be shut down on user service manager exit.

SEE ALSO

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

NOTES

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

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

        3. System Updates Specification
           http://freedesktop.org/wiki/Software/systemd/SystemUpdates