systemd/man/systemd.special.xml

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<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>

</refentry>