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authorZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2015-02-03 21:14:13 -0500
committerZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2015-02-03 23:11:35 -0500
commit798d3a524ea57aaf40cb53858aaa45ec702f012d (patch)
treef9251ab7878a180d464780d514f3ea8d4599fe6e /man/systemd.special.xml
parent35888b67f77fa7a5cae0973403cb97aa30cad70c (diff)
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<?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">
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
@@ -23,1142 +23,854 @@
<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-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>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 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>Usually this should
- pull-in all mount points, swap
- devices, sockets, timers, and
- path units and other basic
- initialization necessary for
- general purpose
- daemons.</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 unit is supposed
- to be used with the kernel
- command line option
- <varname>systemd.unit=</varname>
- and has otherwise little use.
- </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
- for setting up the base system
- and a rescue shell.</para>
-
- <para><filename>runlevel1.target</filename>
- is an alias for this target
- unit, for compatibility with SysV.</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>multi-user.target</filename>
- (for runlevel 2) or
- <filename>graphical.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>
- 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>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>A special target unit
- covering early boot-up scripts.</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 umounts 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>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>
-
- <para>In addition, the following special unit is
- understood only when systemd runs as service instance:</para>
-
- <variablelist>
- <varlistentry>
- <term><filename>exit.target</filename></term>
- <listitem>
- <para>A special service unit
- for shutting down the
- user service manager.</para>
-
- <para>Applications wanting to
- terminate the user service
- manager should start this
- unit. If systemd receives
- <constant>SIGTERM</constant> or <constant>SIGINT</constant> when running
- as user service daemon, it will
- start this unit.</para>
-
- <para>Normally, this pulls in
- <filename>shutdown.target</filename>
- which in turn should be
- conflicted by all units that
- want to be shut down on
- user service manager exit.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </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 services
- 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>
+ <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-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>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 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>Usually this should pull-in all mount points, swap
+ devices, sockets, timers, and path units and other basic
+ initialization necessary for general purpose daemons.</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 unit is supposed to be used with
+ the kernel command line option
+ <varname>systemd.unit=</varname> and has otherwise little
+ use.
+ </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 for setting up the base system
+ and a rescue shell.</para>
+
+ <para><filename>runlevel1.target</filename> is an alias for
+ this target unit, for compatibility with SysV.</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>multi-user.target</filename>
+ (for runlevel 2) or <filename>graphical.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> 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>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>A special target unit covering early boot-up
+ scripts.</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 umounts 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>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>
+
+ <para>In addition, the following special unit is understood only
+ when systemd runs as service instance:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><filename>exit.target</filename></term>
+ <listitem>
+ <para>A special service unit for shutting down the user
+ service manager.</para>
+
+ <para>Applications wanting to terminate the user service
+ manager should start this unit. If systemd receives
+ <constant>SIGTERM</constant> or <constant>SIGINT</constant>
+ when running as user service daemon, it will start this
+ unit.</para>
+
+ <para>Normally, this pulls in
+ <filename>shutdown.target</filename> which in turn should be
+ conflicted by all units that want to be shut down on user
+ service manager exit.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </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 services 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>