From 19f4f86bfed21c5326ed2acebe1163f3a83e832b Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 6 May 2024 04:25:50 +0200 Subject: Adding upstream version 241. Signed-off-by: Daniel Baumann --- man/systemd.special.xml | 1109 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1109 insertions(+) create mode 100644 man/systemd.special.xml (limited to 'man/systemd.special.xml') diff --git a/man/systemd.special.xml b/man/systemd.special.xml new file mode 100644 index 0000000..fd5639b --- /dev/null +++ b/man/systemd.special.xml @@ -0,0 +1,1109 @@ + + + + + + + + + systemd.special + systemd + + + + systemd.special + 7 + + + + systemd.special + Special systemd units + + + + basic.target, + bluetooth.target, + cryptsetup-pre.target, + cryptsetup.target, + ctrl-alt-del.target, + boot-complete.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. + + + + Units managed by the system's service manager + + + 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 + bootup7 + for details on the targets involved. + + + + + boot-complete.target + + This target is intended as generic synchronization point for services that shall determine or act on + whether the boot process completed successfully. Order units that are required to succeed for a boot process + to be considered successful before this unit, and add a Requires= dependency from the + target unit to them. Order units that shall only run when the boot process is considered successful after the + target unit and pull in the target from it, also with Requires=. Note that by default this + target unit is not part of the initial boot transaction, but is supposed to be pulled in only if required by + units that want to run only on successful boots. + + See + systemd-boot-check-no-failures.service8 + for a service that implements a generic system health check and orders itself before + boot-complete.target. + + See + systemd-bless-boot.service8 + for a service that propagates boot success information to the boot loader, and orders itself after + boot-complete.target. + + + + 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 option) or call + systemd1'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-generator3 + automatically adds dependencies of type + Before= to + sysroot-usr.mount and all mount points + found in /etc/fstab that have + and not have + 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-generator3 + and + systemd-gpt-auto-generator3 + automatically setup the appropriate dependencies to make this happen. + + + + + initrd-root-fs.target + + systemd-fstab-generator3 + 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 option) or call + systemd1's + org.freedesktop.systemd1.Manager.KExec D-Bus method + directly. + + + + local-fs.target + + systemd-fstab-generator3 + 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 + 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 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.path5 + 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 option) or call + systemd-logind8'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 option) or call + systemd-logind8'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 + crypttab8 + entries marked with . + + + + 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.slice5 + for details) that shall always be active after boot. By default the generic + system.slice slice unit as well as the root slice unit + -.slice are pulled in and ordered before this unit (see + below). + + Adding slice units to slices.target is generally not + necessary. Instead, when some unit that uses Slice= is started, the + specified slice will be started automatically. Adding + WantedBy=slices.target lines to the [Install] + section should only be done for units that need to be always active. In that case care + needs to be taken to avoid creating a loop through the automatic dependencies on + "parent" slices. + + + + sockets.target + + A special target unit that sets up all socket + units (see + systemd.socket5 + 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 + bootup7. + + + + + 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 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-generator8 + will redirect the boot process to this target if /system-update + exists. For more information see + systemd.offline-updates7. + + + 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.timer5 + 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 + (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 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 . 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 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.slice7 + 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 + + + + + + + + Units managed by the user's service manager + + + 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.unit5. + Those symlinks should either be shipped in packages, or should be added dynamically + after installation, for example using systemctl add-wants, see + systemctl1. + + + + 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. + + + + + + + + See Also + + systemd1, + systemd.unit5, + systemd.service5, + systemd.socket5, + systemd.target5, + systemd.slice5, + bootup7, + systemd-fstab-generator8, + user@.service5 + + + + -- cgit v1.2.3