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diff --git a/src/grp-system/systemd/systemd.special.xml b/src/grp-system/systemd/systemd.special.xml new file mode 100644 index 0000000000..d977298cd8 --- /dev/null +++ b/src/grp-system/systemd/systemd.special.xml @@ -0,0 +1,1005 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + This file is part of systemd. + + Copyright 2010 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<refentry id="systemd.special"> + + <refentryinfo> + <title>systemd.special</title> + <productname>systemd</productname> + + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Lennart</firstname> + <surname>Poettering</surname> + <email>lennart@poettering.net</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>systemd.special</refentrytitle> + <manvolnum>7</manvolnum> + </refmeta> + + <refnamediv> + <refname>systemd.special</refname> + <refpurpose>Special systemd units</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <para><filename>basic.target</filename>, + <filename>bluetooth.target</filename>, + <filename>ctrl-alt-del.target</filename>, + <filename>cryptsetup.target</filename>, + <filename>cryptsetup-pre.target</filename>, + <filename>dbus.service</filename>, + <filename>dbus.socket</filename>, + <filename>default.target</filename>, + <filename>display-manager.service</filename>, + <filename>emergency.target</filename>, + <filename>exit.target</filename>, + <filename>final.target</filename>, + <filename>getty.target</filename>, + <filename>graphical.target</filename>, + <filename>halt.target</filename>, + <filename>hibernate.target</filename>, + <filename>hybrid-sleep.target</filename>, + <filename>initrd-fs.target</filename>, + <filename>kbrequest.target</filename>, + <filename>kexec.target</filename>, + <filename>local-fs.target</filename>, + <filename>local-fs-pre.target</filename>, + <filename>multi-user.target</filename>, + <filename>network.target</filename>, + <filename>network-online.target</filename>, + <filename>network-pre.target</filename>, + <filename>nss-lookup.target</filename>, + <filename>nss-user-lookup.target</filename>, + <filename>paths.target</filename>, + <filename>poweroff.target</filename>, + <filename>printer.target</filename>, + <filename>reboot.target</filename>, + <filename>remote-fs.target</filename>, + <filename>remote-fs-pre.target</filename>, + <filename>rescue.target</filename>, + <filename>initrd-root-device.target</filename>, + <filename>initrd-root-fs.target</filename>, + <filename>rpcbind.target</filename>, + <filename>runlevel2.target</filename>, + <filename>runlevel3.target</filename>, + <filename>runlevel4.target</filename>, + <filename>runlevel5.target</filename>, + <filename>shutdown.target</filename>, + <filename>sigpwr.target</filename>, + <filename>sleep.target</filename>, + <filename>slices.target</filename>, + <filename>smartcard.target</filename>, + <filename>sockets.target</filename>, + <filename>sound.target</filename>, + <filename>suspend.target</filename>, + <filename>swap.target</filename>, + <filename>sysinit.target</filename>, + <filename>syslog.socket</filename>, + <filename>system-update.target</filename>, + <filename>time-sync.target</filename>, + <filename>timers.target</filename>, + <filename>umount.target</filename>, + <filename>-.slice</filename>, + <filename>system.slice</filename>, + <filename>user.slice</filename>, + <filename>machine.slice</filename></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para>A few units are treated specially by systemd. They have + special internal semantics and cannot be renamed.</para> + </refsect1> + + <refsect1> + <title>Special System Units</title> + + <variablelist> + <varlistentry> + <term><filename>basic.target</filename></term> + <listitem> + <para>A special target unit covering basic boot-up.</para> + + <para>systemd automatically adds dependency of the type + <varname>After=</varname> for this target unit to all + services (except for those with + <varname>DefaultDependencies=no</varname>).</para> + + <para>Usually, this should pull-in all local mount points plus + <filename>/var</filename>, <filename>/tmp</filename> and + <filename>/var/tmp</filename>, 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. + </para> + + <para>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 + <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> + for details on the targets involved. + </para> + + </listitem> + </varlistentry> + <varlistentry> + <term><filename>ctrl-alt-del.target</filename></term> + <listitem> + <para>systemd starts this target whenever Control+Alt+Del is + pressed on the console. Usually, this should be aliased + (symlinked) to <filename>reboot.target</filename>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>cryptsetup.target</filename></term> + <listitem> + <para>A target that pulls in setup services for all + encrypted block devices.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>dbus.service</filename></term> + <listitem> + <para>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.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>dbus.socket</filename></term> + <listitem> + <para>A special unit for the D-Bus system bus socket. All + units with <varname>Type=dbus</varname> automatically gain a + dependency on this unit.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>default.target</filename></term> + <listitem> + <para>The default unit systemd starts at bootup. Usually, + this should be aliased (symlinked) to + <filename>multi-user.target</filename> or + <filename>graphical.target</filename>.</para> + + <para>The default unit systemd starts at bootup can be + overridden with the <varname>systemd.unit=</varname> kernel + command line option.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>display-manager.service</filename></term> + <listitem> + <para>The display manager service. Usually, this should be + aliased (symlinked) to <filename>gdm.service</filename> or a + similar display manager service.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>emergency.target</filename></term> + <listitem> + <para>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 + <varname>systemd.unit=</varname>; it is also used when a file system check on a required file system fails, + and boot-up cannot continue. Compare with <filename>rescue.target</filename>, which serves a similar purpose, + but also starts the most basic services and mounts all file systems.</para> + + <para>Use the <literal>systemd.unit=emergency.target</literal> kernel command line option to boot into this + mode. A short alias for this kernel command line option is <literal>emergency</literal>, for compatibility + with SysV.</para> + + <para>In many ways booting into <filename>emergency.target</filename> is similar to the effect of booting + with <literal>init=/bin/sh</literal> 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.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>exit.target</filename></term> + <listitem> + <para>A special service unit for shutting down the system or + user service manager. It is equivalent to + <filename>poweroff.target</filename> on non-container + systems, and also works in containers.</para> + + <para>systemd will start this unit when it receives a + request to shut down over D-Bus or a + <constant>SIGTERM</constant> or <constant>SIGINT</constant> + signal when running as user service daemon.</para> + + <para>Normally, this (indirectly) pulls in + <filename>shutdown.target</filename>, which in turn should be + conflicted by all units that want to be scheduled for + shutdown when the service manager starts to exit.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>final.target</filename></term> + <listitem> + <para>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. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>getty.target</filename></term> + <listitem> + <para>A special target unit that pulls in statically + configured local TTY <filename>getty</filename> instances. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>graphical.target</filename></term> + <listitem> + <para>A special target unit for setting up a graphical login + screen. This pulls in + <filename>multi-user.target</filename>.</para> + + <para>Units that are needed for graphical logins shall add + <varname>Wants=</varname> dependencies for their unit to + this unit (or <filename>multi-user.target</filename>) during + installation. This is best configured via + <varname>WantedBy=graphical.target</varname> in the unit's + <literal>[Install]</literal> section.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>hibernate.target</filename></term> + <listitem> + <para>A special target unit for hibernating the system. This + pulls in <filename>sleep.target</filename>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>hybrid-sleep.target</filename></term> + <listitem> + <para>A special target unit for hibernating and suspending + the system at the same time. This pulls in + <filename>sleep.target</filename>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>halt.target</filename></term> + <listitem> + <para>A special target unit for shutting down and halting + the system. Note that this target is distinct from + <filename>poweroff.target</filename> in that it generally + really just halts the system rather than powering it + down.</para> + + <para>Applications wanting to halt the system should start + this unit.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>initrd-fs.target</filename></term> + <listitem> + <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry> + automatically adds dependencies of type + <varname>Before=</varname> to + <filename>sysroot-usr.mount</filename> and all mount points + found in <filename>/etc/fstab</filename> that have + <option>x-initrd.mount</option> and not have + <option>noauto</option> mount options set.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>kbrequest.target</filename></term> + <listitem> + <para>systemd starts this target whenever Alt+ArrowUp is + pressed on the console. This is a good candidate to be + aliased (symlinked) to + <filename>rescue.target</filename>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>kexec.target</filename></term> + <listitem> + <para>A special target unit for shutting down and rebooting + the system via kexec.</para> + + <para>Applications wanting to reboot the system with kexec + should start this unit.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>local-fs.target</filename></term> + <listitem> + <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry> + automatically adds dependencies of type + <varname>Before=</varname> to all mount units that refer to + local mount points for this target unit. In addition, it + adds dependencies of type <varname>Wants=</varname> to this + target unit for those mounts listed in + <filename>/etc/fstab</filename> that have the + <option>auto</option> mount option set.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>multi-user.target</filename></term> + <listitem> + <para>A special target unit for setting up a multi-user + system (non-graphical). This is pulled in by + <filename>graphical.target</filename>.</para> + + <para>Units that are needed for a multi-user system shall + add <varname>Wants=</varname> dependencies for their unit to + this unit during installation. This is best configured via + <varname>WantedBy=multi-user.target</varname> in the unit's + <literal>[Install]</literal> section.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>network-online.target</filename></term> + <listitem> + <para>Units that strictly require a configured network + connection should pull in + <filename>network-online.target</filename> (via a + <varname>Wants=</varname> 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.</para> + + <para>Note the distinction between this unit and + <filename>network.target</filename>. 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, <filename>network.target</filename> 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, <filename>network.target</filename> + is part of the boot of most systems, while + <filename>network-online.target</filename> is not, except + when at least one unit requires it. Also see <ulink + url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running + Services After the Network is up</ulink> for more + information.</para> + + <para>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.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>paths.target</filename></term> + <listitem> + <para>A special target unit that sets up all path units (see + <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details) that shall be active after boot.</para> + + <para>It is recommended that path units installed by + applications get pulled in via <varname>Wants=</varname> + dependencies from this unit. This is best configured via a + <varname>WantedBy=paths.target</varname> in the path unit's + <literal>[Install]</literal> section.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>poweroff.target</filename></term> + <listitem> + <para>A special target unit for shutting down and powering + off the system.</para> + + <para>Applications wanting to power off the system should + start this unit.</para> + + <para><filename>runlevel0.target</filename> is an alias for + this target unit, for compatibility with SysV.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>reboot.target</filename></term> + <listitem> + <para>A special target unit for shutting down and rebooting + the system.</para> + + <para>Applications wanting to reboot the system should start + this unit.</para> + + <para><filename>runlevel6.target</filename> is an alias for + this target unit, for compatibility with SysV.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>remote-fs.target</filename></term> + <listitem> + <para>Similar to <filename>local-fs.target</filename>, but + for remote mount points.</para> + + <para>systemd automatically adds dependencies of type + <varname>After=</varname> for this target unit to all SysV + init script service units with an LSB header referring to + the <literal>$remote_fs</literal> facility.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>rescue.target</filename></term> + <listitem> + <para>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 + <filename>emergency.target</filename>, which is much more reduced and does not provide the file systems or + most basic services.</para> + + <para><filename>runlevel1.target</filename> is an alias for this target unit, for compatibility with + SysV.</para> + + <para>Use the <literal>systemd.unit=rescue.target</literal> kernel command line option to boot into this + mode. A short alias for this kernel command line option is <literal>1</literal>, for compatibility with + SysV.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>initrd-root-device.target</filename></term> + <listitem> + <para>A special initrd target unit that is reached when the root filesystem device is available, but before + it has been mounted. + <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry> + and + <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry> + automatically setup the appropriate dependencies to make this happen. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>initrd-root-fs.target</filename></term> + <listitem> + <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry> + automatically adds dependencies of type + <varname>Before=</varname> to the + <filename>sysroot.mount</filename> unit, which is generated + from the kernel command line. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>runlevel2.target</filename></term> + <term><filename>runlevel3.target</filename></term> + <term><filename>runlevel4.target</filename></term> + <term><filename>runlevel5.target</filename></term> + <listitem> + <para>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) <filename>graphical.target</filename> + (for runlevel 5) or <filename>multi-user.target</filename> + (the others).</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>shutdown.target</filename></term> + <listitem> + <para>A special target unit that terminates the services on + system shutdown.</para> + + <para>Services that shall be terminated on system shutdown + shall add <varname>Conflicts=</varname> and + <varname>Before=</varname> dependencies to this unit for + their service unit, which is implicitly done when + <varname>DefaultDependencies=yes</varname> is set (the + default).</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>sigpwr.target</filename></term> + <listitem> + <para>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.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>sleep.target</filename></term> + <listitem> + <para>A special target unit that is pulled in by + <filename>suspend.target</filename>, + <filename>hibernate.target</filename> and + <filename>hybrid-sleep.target</filename> and may be used to + hook units into the sleep state logic.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>slices.target</filename></term> + <listitem> + <para>A special target unit that sets up all slice units (see + <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry> for + details) that shall be active after boot. By default the generic <filename>user.slice</filename>, + <filename>system.slice</filename>, <filename>machines.slice</filename> slice units, as well as the root + slice unit <filename>-.slice</filename> are pulled in and ordered before this unit (see below).</para> + + <para>It's a good idea to add <varname>WantedBy=slices.target</varname> lines to the <literal>[Install]</literal> + section of all slices units that may be installed dynamically.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>sockets.target</filename></term> + <listitem> + <para>A special target unit that sets up all socket + units (see + <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details) that shall be active after boot.</para> + + <para>Services that can be socket-activated shall add + <varname>Wants=</varname> dependencies to this unit for + their socket unit during installation. This is best + configured via a <varname>WantedBy=sockets.target</varname> + in the socket unit's <literal>[Install]</literal> + section.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>suspend.target</filename></term> + <listitem> + <para>A special target unit for suspending the system. This + pulls in <filename>sleep.target</filename>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>swap.target</filename></term> + <listitem> + <para>Similar to <filename>local-fs.target</filename>, but + for swap partitions and swap files.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>sysinit.target</filename></term> + <listitem> + <para>systemd automatically adds dependencies of the types + <varname>Requires=</varname> and <varname>After=</varname> + for this target unit to all services (except for those with + <varname>DefaultDependencies=no</varname>).</para> + + <para>This target pulls in the services required for system + initialization. System services pulled in by this target should + declare <varname>DefaultDependencies=no</varname> 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 + <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>syslog.socket</filename></term> + <listitem> + <para>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 <ulink + url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog + Interface</ulink> document.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>system-update.target</filename></term> + <listitem> + <para>A special target unit that is used for off-line system + updates. + <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry> + will redirect the boot process to this target if + <filename>/system-update</filename> exists. For more + information see the <ulink + url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System + Updates Specification</ulink>.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>timers.target</filename></term> + <listitem> + <para>A special target unit that sets up all timer units + (see + <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details) that shall be active after boot.</para> + + <para>It is recommended that timer units installed by + applications get pulled in via <varname>Wants=</varname> + dependencies from this unit. This is best configured via + <varname>WantedBy=timers.target</varname> in the timer + unit's <literal>[Install]</literal> section.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>umount.target</filename></term> + <listitem> + <para>A special target unit that unmounts all mount and + automount points on system shutdown.</para> + + <para>Mounts that shall be unmounted on system shutdown + shall add Conflicts dependencies to this unit for their + mount unit, which is implicitly done when + <varname>DefaultDependencies=yes</varname> is set (the + default).</para> + </listitem> + </varlistentry> + + </variablelist> + </refsect1> + + <refsect1> + <title>Special System Units for Devices</title> + + <para>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.</para> + + <variablelist> + <varlistentry> + <term><filename>bluetooth.target</filename></term> + <listitem> + <para>This target is started automatically as soon as a + Bluetooth controller is plugged in or becomes available at + boot.</para> + + <para>This may be used to pull in Bluetooth management + daemons dynamically when Bluetooth hardware is found.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>printer.target</filename></term> + <listitem> + <para>This target is started automatically as soon as a + printer is plugged in or becomes available at boot.</para> + + <para>This may be used to pull in printer management daemons + dynamically when printer hardware is found.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>smartcard.target</filename></term> + <listitem> + <para>This target is started automatically as soon as a + smartcard controller is plugged in or becomes available at + boot.</para> + + <para>This may be used to pull in smartcard management + daemons dynamically when smartcard hardware is found.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>sound.target</filename></term> + <listitem> + <para>This target is started automatically as soon as a + sound card is plugged in or becomes available at + boot.</para> + + <para>This may be used to pull in audio management daemons + dynamically when audio hardware is found.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Special Passive System Units </title> + + <para>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 <emphasis>passive</emphasis> 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 + <varname>Wants=</varname> type dependency).</para> + + <para>Note that these passive units cannot be started manually, + i.e. <literal>systemctl start time-sync.target</literal> 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.</para> + + <variablelist> + <varlistentry> + <term><filename>cryptsetup-pre.target</filename></term> + <listitem> + <para>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.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>local-fs-pre.target</filename></term> + <listitem> + <para>This target unit is + automatically ordered before + all local mount points marked + with <option>auto</option> + (see above). It can be used to + execute certain units before + all local mounts.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>network.target</filename></term> + <listitem> + <para>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 + <filename>network.target</filename> 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 + <ulink url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running + Services After the Network is up</ulink> for more + information. Also see + <filename>network-online.target</filename> described + above.</para> + + <para>systemd automatically adds dependencies of type + <varname>After=</varname> for this target unit to all SysV + init script service units with an LSB header referring to + the <literal>$network</literal> facility.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>network-pre.target</filename></term> + <listitem> + <para>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.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>nss-lookup.target</filename></term> + <listitem> + <para>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 + <filename>nss-user-lookup.target</filename> 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 <varname>After=</varname> for this + target unit to all SysV init script service units with an + LSB header referring to the <literal>$named</literal> + facility.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>nss-user-lookup.target</filename></term> + <listitem> + <para>A target that should be used as synchronization point + for all user/group name service lookups. Note that this is + independent of host/network name lookups for which + <filename>nss-lookup.target</filename> should be used. All + services for which the availability of the full user/group + database is essential should be ordered after this target, + but not pull it in. Note that system users are always + resolvable, and hence do not require any special ordering + against this target.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>remote-fs-pre.target</filename></term> + <listitem> + <para>This target unit is automatically ordered before all + remote mount point units (see above). It can be used to run + certain units before the remote mounts are established. Note + that this unit is generally not part of the initial + transaction, unless the unit that wants to be ordered before + all remote mounts pulls it in via a + <varname>Wants=</varname> type dependency. If the unit wants + to be pulled in by the first remote mount showing up, it + should use <filename>network-online.target</filename> (see + above).</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>rpcbind.target</filename></term> + <listitem> + <para>The portmapper/rpcbind pulls in this target and orders + itself before it, to indicate its availability. systemd + automatically adds dependencies of type + <varname>After=</varname> for this target unit to all SysV + init script service units with an LSB header referring to + the <literal>$portmap</literal> facility.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>time-sync.target</filename></term> + <listitem> + <para>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 + <varname>After=</varname> for this target unit to all SysV + init script service units with an LSB header referring to + the <literal>$time</literal> facility. </para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Special User Units</title> + + <para>When systemd runs as a user instance, the following special + units are available, which have similar definitions as their + system counterparts: + <filename>exit.target</filename>, + <filename>default.target</filename>, + <filename>shutdown.target</filename>, + <filename>sockets.target</filename>, + <filename>timers.target</filename>, + <filename>paths.target</filename>, + <filename>bluetooth.target</filename>, + <filename>printer.target</filename>, + <filename>smartcard.target</filename>, + <filename>sound.target</filename>.</para> + </refsect1> + + <refsect1> + <title>Special Passive User Units</title> + + <refsect2> + <title>graphical-session.target</title> + + <para>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 <literal>PartOf=graphical-session.target</literal> in their + <literal>[Unit]</literal> section. A target for a particular session + (e. g. <filename>gnome-session.target</filename>) starts and stops + <literal>graphical-session.target</literal> with + <literal>BindsTo=graphical-session.target</literal>.</para> + + <para>Which services are started by a session target is determined by the + <literal>Wants=</literal> and <literal>Requires=</literal> dependencies. + For services that can be enabled independently, symlinks in + <literal>.wants/</literal> and <literal>.requires/</literal> should be + used, see + <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + Those symlinks should either be shipped in packages, or should be added + dynamically after installation, for example using <literal>systemctl add-wants</literal>, see + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. + </para> + + <example> + <title>Nautilus as part of a GNOME session</title> + + <para><literal>gnome-session.target</literal> pulls in Nautilus as + top-level service:</para> + + <programlisting>[Unit] +Description=User systemd services for GNOME graphical session +Wants=nautilus.service +BindsTo=graphical-session.target + </programlisting> + + <para><literal>nautilus.service</literal> gets stopped when the session stops:</para> + + <programlisting>[Unit] +Description=Render the desktop icons with Nautilus +PartOf=graphical-session.target + +[Service] +... + </programlisting> + </example> + </refsect2> + + <refsect2> + <title>graphical-session-pre.target</title> + + <para>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 <filename>gnome-session.target</filename>.</para> + </refsect2> + + </refsect1> + + <refsect1> + <title>Special Slice Units</title> + + <para>There are four <literal>.slice</literal> units which form + the basis of the hierarchy for assignment of resources for + services, users, and virtual machines or containers.</para> + + <variablelist> + <varlistentry> + <term><filename>-.slice</filename></term> + <listitem> + <para>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.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><filename>system.slice</filename></term> + <listitem> + <para>By default, all system services started by + <command>systemd</command> are found in this slice.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><filename>user.slice</filename></term> + <listitem> + <para>By default, all user processes and services started on + behalf of the user, including the per-user systemd instance + are found in this slice.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><filename>machine.slice</filename></term> + <listitem> + <para>By default, all virtual machines and containers + registered with <command>systemd-machined</command> are + found in this slice. + </para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |