<filename>remote-fs.target</filename>,
<filename>remote-fs-pre.target</filename>,
<filename>rescue.target</filename>,
+ <filename>initrd-root-device.target</filename>,
<filename>initrd-root-fs.target</filename>,
<filename>rpcbind.target</filename>,
<filename>runlevel2.target</filename>,
<filename>shutdown.target</filename>,
<filename>sigpwr.target</filename>,
<filename>sleep.target</filename>,
+ <filename>slices.target</filename>,
<filename>smartcard.target</filename>,
<filename>sockets.target</filename>,
<filename>sound.target</filename>,
<filename>sysinit.target</filename>,
<filename>syslog.socket</filename>,
<filename>system-update.target</filename>,
+ <filename>system-update-cleanup.service</filename>,
<filename>time-sync.target</filename>,
<filename>timers.target</filename>,
<filename>umount.target</filename>,
<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
+ <para>systemd automatically adds dependency of the type
+ <varname>After=</varname> for this target unit to all
+ services (except for those with
<varname>DefaultDependencies=no</varname>).</para>
<para>Usually, this should pull-in all local mount points plus
<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>
+ <para>A special target unit that starts an emergency shell on the main console. This target does not pull in
+ any services or mounts. It is the most minimal version of starting the system in order to acquire an
+ interactive shell; the only processes running are usually just the system manager (PID 1) and the shell
+ process. This unit is supposed to be used with the kernel command line option
+ <varname>systemd.unit=</varname>; it is also used when a file system check on a required file system fails,
+ and boot-up cannot continue. Compare with <filename>rescue.target</filename>, which serves a similar purpose,
+ but also starts the most basic services and mounts all file systems.</para>
+
+ <para>Use the <literal>systemd.unit=emergency.target</literal> kernel command line option to boot into this
+ mode. A short alias for this kernel command line option is <literal>emergency</literal>, for compatibility
+ with SysV.</para>
+
+ <para>In many ways booting into <filename>emergency.target</filename> is similar to the effect of booting
+ with <literal>init=/bin/sh</literal> on the kernel command line, except that emergency mode provides you with
+ the full system and service manager, and allows starting individual units in order to continue the boot
+ process in steps.</para>
</listitem>
</varlistentry>
<varlistentry>
<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>A special target unit that pulls in the base system (including system mounts) and spawns a rescue
+ shell. Isolate to this target in order to administer the system in single-user mode with all file systems
+ mounted but with no services running, except for the most basic. Compare with
+ <filename>emergency.target</filename>, which is much more reduced and does not provide the file systems or
+ most basic services.</para>
- <para><filename>runlevel1.target</filename> is an alias for
- this target unit, for compatibility with SysV.</para>
+ <para><filename>runlevel1.target</filename> is an alias for this target unit, for compatibility with
+ SysV.</para>
+
+ <para>Use the <literal>systemd.unit=rescue.target</literal> kernel command line option to boot into this
+ mode. A short alias for this kernel command line option is <literal>1</literal>, for compatibility with
+ SysV.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><filename>initrd-root-device.target</filename></term>
+ <listitem>
+ <para>A special initrd target unit that is reached when the root filesystem device is available, but before
+ it has been mounted.
+ <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ and
+ <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ automatically setup the appropriate dependencies to make this happen.
+ </para>
</listitem>
</varlistentry>
<varlistentry>
<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>
+ (i.e. symlink to) <filename>graphical.target</filename>
+ (for runlevel 5) or <filename>multi-user.target</filename>
(the others).</para>
</listitem>
</varlistentry>
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
+ shall add <varname>Conflicts=</varname> and
+ <varname>Before=</varname> dependencies to this unit for
+ their service unit, which is implicitly done when
<varname>DefaultDependencies=yes</varname> is set (the
default).</para>
</listitem>
hook units into the sleep state logic.</para>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><filename>slices.target</filename></term>
+ <listitem>
+ <para>A special target unit that sets up all slice units (see
+ <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
+ details) that shall be active after boot. By default the generic <filename>user.slice</filename>,
+ <filename>system.slice</filename>, <filename>machines.slice</filename> slice units, as well as the root
+ slice unit <filename>-.slice</filename> are pulled in and ordered before this unit (see below).</para>
+
+ <para>It's a good idea to add <varname>WantedBy=slices.target</varname> lines to the <literal>[Install]</literal>
+ section of all slices units that may be installed dynamically.</para>
+ </listitem>
+ </varlistentry>
<varlistentry>
<term><filename>sockets.target</filename></term>
<listitem>
<para>A special target unit that sets up all socket
- units.(see
+ units (see
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details) that shall be active after boot.</para>
<varlistentry>
<term><filename>sysinit.target</filename></term>
<listitem>
+ <para>systemd automatically adds dependencies of the types
+ <varname>Requires=</varname> and <varname>After=</varname>
+ for this target unit to all services (except for those with
+ <varname>DefaultDependencies=no</varname>).</para>
+
<para>This target pulls in the services required for system
initialization. System services pulled in by this target should
declare <varname>DefaultDependencies=no</varname> and specify
</varlistentry>
<varlistentry>
<term><filename>system-update.target</filename></term>
+ <term><filename>system-update-cleanup.service</filename></term>
<listitem>
- <para>A special target unit that is used for off-line system
- updates.
+ <para>A special target unit that is used for offline 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>
+ will redirect the boot process to this target if <filename>/system-update</filename>
+ exists. For more information see
+ <citerefentry><refentrytitle>systemd.offline-updates</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ </para>
+
+ <para>Updates should happen before the <filename>system-update.target</filename> is
+ reached, and the services which implement them should cause the machine to reboot. As
+ a safety measure, if this does not happen, and <filename>/system-update</filename>
+ still exists after <filename>system-update.target</filename> is reached,
+ <filename>system-update-cleanup.service</filename> will remove this symlink and
+ reboot the machine.</para>
</listitem>
</varlistentry>
<varlistentry>
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 --
+ 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
<filename>sound.target</filename>.</para>
</refsect1>
+ <refsect1>
+ <title>Special Passive User Units</title>
+
+ <refsect2>
+ <title>graphical-session.target</title>
+
+ <para>This target is active whenever any graphical session is running. It
+ is used to stop user services which only apply to a graphical (X,
+ Wayland, etc.) session when the session is terminated. Such services
+ should have <literal>PartOf=graphical-session.target</literal> in their
+ <literal>[Unit]</literal> section. A target for a particular session
+ (e. g. <filename>gnome-session.target</filename>) starts and stops
+ <literal>graphical-session.target</literal> with
+ <literal>BindsTo=graphical-session.target</literal>.</para>
+
+ <para>Which services are started by a session target is determined by the
+ <literal>Wants=</literal> and <literal>Requires=</literal> dependencies.
+ For services that can be enabled independently, symlinks in
+ <literal>.wants/</literal> and <literal>.requires/</literal> should be
+ used, see
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ Those symlinks should either be shipped in packages, or should be added
+ dynamically after installation, for example using <literal>systemctl add-wants</literal>, see
+ <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
+ </para>
+
+ <example>
+ <title>Nautilus as part of a GNOME session</title>
+
+ <para><literal>gnome-session.target</literal> pulls in Nautilus as
+ top-level service:</para>
+
+ <programlisting>[Unit]
+Description=User systemd services for GNOME graphical session
+Wants=nautilus.service
+BindsTo=graphical-session.target
+ </programlisting>
+
+ <para><literal>nautilus.service</literal> gets stopped when the session stops:</para>
+
+ <programlisting>[Unit]
+Description=Render the desktop icons with Nautilus
+PartOf=graphical-session.target
+
+[Service]
+…
+ </programlisting>
+ </example>
+ </refsect2>
+
+ <refsect2>
+ <title>graphical-session-pre.target</title>
+
+ <para>This target contains services which set up the environment or
+ global configuration of a graphical session, such as SSH/GPG agents
+ (which need to export an environment variable into all desktop processes)
+ or migration of obsolete d-conf keys after an OS upgrade (which needs to
+ happen before starting any process that might use them). This target must
+ be started before starting a graphical session
+ like <filename>gnome-session.target</filename>.</para>
+ </refsect2>
+
+ </refsect1>
+
<refsect1>
<title>Special Slice Units</title>
projects / thirdparty / systemd.git / blobdiff