systemd.special(7)



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

NAME
       systemd.special - Special systemd units

SYNOPSIS
       basic.target, bluetooth.target, cryptsetup-pre.target,
       cryptsetup.target, ctrl-alt-del.target, default.target,
       emergency.target, exit.target, final.target, getty.target,
       getty-pre.target, graphical.target, halt.target, hibernate.target,
       hybrid-sleep.target, suspend-then-hibernate.target, initrd-fs.target,
       initrd-root-device.target, initrd-root-fs.target, kbrequest.target,
       kexec.target, local-fs-pre.target, local-fs.target, machines.target
       multi-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-cryptsetup.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,
       system-update.target, system-update-pre.target, time-sync.target,
       timers.target, umount.target, -.slice, system.slice, user.slice,
       machine.slice, -.mount, dbus.service, dbus.socket,
       display-manager.service, init.scope, syslog.socket,
       system-update-cleanup.service

DESCRIPTION
       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
       -.mount
           The root mount point, i.e. the mount unit for the / path. This unit
           is unconditionally active, during the entire time the system is up,
           as this mount point is where the basic userspace is running from.

       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 the 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.

       suspend-then-hibernate.target
           A special target unit for suspending the system for a period of
           time, waking it and putting it into hibernate. 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 not start this unit
           directly, but should instead execute systemctl halt (possibly with
           the --no-block option) or call systemd(1)'s
           org.freedesktop.systemd1.Manager.Halt D-Bus method directly.

       init.scope
           This scope unit is where the system and service manager (PID 1)
           itself resides. It is active as long as the system is running.

       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.

       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.

       kbrequest.target
           systemd starts this target whenever Alt+ArrowUp is pressed on the
           console. Note that any user with physical access to the machine
           will be able to do this, without authentication, so this should be
           used carefully.

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

           Applications wanting to reboot the system should not start this
           unit directly, but should instead execute systemctl kexec (possibly
           with the --no-block option) or call systemd(1)'s
           org.freedesktop.systemd1.Manager.KExec D-Bus method directly.

       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.

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

           Note that this unit is only useful during the original system
           start-up logic. After the system has completed booting up, it will
           not track the online state of the system anymore. Due to this it
           cannot be used as a network connection monitor concept, it is
           purely a one-time system start-up concept.

       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 not start this
           unit directly, but should instead execute systemctl poweroff
           (possibly with the --no-block option) or call systemd-logind(8)'s
           org.freedesktop.login1.Manager.PowerOff D-Bus method directly.

           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 not start this
           unit directly, but should instead execute systemctl reboot
           (possibly with the --no-block option) or call systemd-logind(8)'s
           org.freedesktop.login1.Manager.Reboot D-Bus method directly.

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

       remote-cryptsetup.target
           Similar to cryptsetup.target, but for encrypted devices which are
           accessed over the network. It is used for crypttab(8) entries
           marked with _netdev.

       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.
           Compare with multi-user.target, this target could be seen as
           single-user.target.

           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.

       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 system.slice slice unit, as well as the root
           slice unit -.slice, is 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-pre.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. The main units executing the update should order themselves
           after system-update-pre.target but not pull it in. Services which
           want to run during system updates only, but before the actual
           system update is executed should order themselves before this unit
           and pull it in. 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
       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.

       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.

       getty-pre.target
           A special passive target unit. Users of this target are expected to
           pull it in the boot transaction via a dependency (e.g.  Wants=).
           Order your unit before this unit if you want to make use of the
           console just before getty is started.

       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.

       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
           UNIX 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
           regular UNIX 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. All services which
           provide parts of the user/group database should be ordered before
           this target, and pull it in. Note that this unit is only relevant
           for regular users and groups -- system users and groups are
           required to be resolvable during earliest boot already, and hence
           do not need any special ordering against this target.

       remote-fs-pre.target
           This target unit is automatically ordered before all mount point
           units (see above) and cryptsetup devices marked with the _netdev.
           It can be used to run certain units before remote encrypted devices
           and 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
       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
       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
       There are four ".slice" units which form the basis of the hierarchy for
       assignment of resources for services, users, and virtual machines or
       containers. See systemd.slice(7) for details about slice units.

       -.slice
           The root slice is the root of the slice 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. This is pulled in by systemd-logind.service

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

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

NOTES
        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

systemd 239                                                 SYSTEMD.SPECIAL(7)

Man(1) output converted with man2html
list of all man pages