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https://github.com/systemd/systemd-stable.git
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1392 lines
70 KiB
XML
1392 lines
70 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd.special">
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<refentryinfo>
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<title>systemd.special</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd.special</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.special</refname>
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<refpurpose>Special systemd units</refpurpose>
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</refnamediv>
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<refsynopsisdiv><para>
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<!-- sort alphabetically, targets first --><filename>basic.target</filename>,
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<filename>bluetooth.target</filename>,
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<filename>cryptsetup-pre.target</filename>,
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<filename>cryptsetup.target</filename>,
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<filename>veritysetup-pre.target</filename>,
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<filename>veritysetup.target</filename>,
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<filename>ctrl-alt-del.target</filename>,
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<filename>blockdev@.target</filename>,
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<filename>boot-complete.target</filename>,
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<filename>default.target</filename>,
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<filename>emergency.target</filename>,
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<filename>exit.target</filename>,
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<filename>factory-reset.target</filename>,
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<filename>final.target</filename>,
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<filename>first-boot-complete.target</filename>,
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<filename>getty.target</filename>,
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<filename>getty-pre.target</filename>,
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<filename>graphical.target</filename>,
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<filename>halt.target</filename>,
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<filename>hibernate.target</filename>,
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<filename>hybrid-sleep.target</filename>,
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<filename>suspend-then-hibernate.target</filename>,
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<filename>initrd.target</filename>,
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<filename>initrd-fs.target</filename>,
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<filename>initrd-root-device.target</filename>,
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<filename>initrd-root-fs.target</filename>,
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<filename>initrd-usr-fs.target</filename>,
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<filename>integritysetup-pre.target</filename>,
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<filename>integritysetup.target</filename>,
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<filename>kbrequest.target</filename>,
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<filename>kexec.target</filename>,
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<filename>local-fs-pre.target</filename>,
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<filename>local-fs.target</filename>,
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<filename>machines.target</filename>
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<filename>multi-user.target</filename>,
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<filename>network-online.target</filename>,
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<filename>network-pre.target</filename>,
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<filename>network.target</filename>,
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<filename>nss-lookup.target</filename>,
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<filename>nss-user-lookup.target</filename>,
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<filename>paths.target</filename>,
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<filename>poweroff.target</filename>,
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<filename>printer.target</filename>,
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<filename>reboot.target</filename>,
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<filename>remote-cryptsetup.target</filename>,
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<filename>remote-veritysetup.target</filename>,
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<filename>remote-fs-pre.target</filename>,
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<filename>remote-fs.target</filename>,
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<filename>rescue.target</filename>,
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<filename>rpcbind.target</filename>,
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<filename>runlevel2.target</filename>,
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<filename>runlevel3.target</filename>,
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<filename>runlevel4.target</filename>,
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<filename>runlevel5.target</filename>,
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<filename>shutdown.target</filename>,
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<filename>sigpwr.target</filename>,
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<filename>sleep.target</filename>,
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<filename>slices.target</filename>,
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<filename>smartcard.target</filename>,
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<filename>sockets.target</filename>,
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<filename>sound.target</filename>,
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<filename>suspend.target</filename>,
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<filename>swap.target</filename>,
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<filename>sysinit.target</filename>,
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<filename>system-update.target</filename>,
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<filename>system-update-pre.target</filename>,
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<filename>time-set.target</filename>,
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<filename>time-sync.target</filename>,
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<filename>timers.target</filename>,
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<filename>umount.target</filename>,
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<filename>usb-gadget.target</filename>,
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<!-- slices --><filename>-.slice</filename>,
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<filename>system.slice</filename>,
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<filename>user.slice</filename>,
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<filename>machine.slice</filename>,
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<!-- the rest --><filename>-.mount</filename>,
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<filename>dbus.service</filename>,
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<filename>dbus.socket</filename>,
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<filename>display-manager.service</filename>,
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<filename>init.scope</filename>,
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<filename>syslog.socket</filename>,
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<filename>system-update-cleanup.service</filename>
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</para></refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>A few units are treated specially by systemd. Many of them have
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special internal semantics and cannot be renamed, while others simply
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have a standard meaning and should be present on all systems.</para>
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</refsect1>
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<refsect1>
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<title>Units managed by the system service manager</title>
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<refsect2>
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<title>Special System Units</title>
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<variablelist>
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<varlistentry>
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<term><filename>-.mount</filename></term>
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<listitem>
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<para>The root mount point, i.e. the mount unit for the <filename>/</filename>
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path. This unit is unconditionally active, during the entire time the system is up, as
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this mount point is where the basic userspace is running from.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>basic.target</filename></term>
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<listitem>
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<para>A special target unit covering basic boot-up.</para>
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<para>systemd automatically adds dependency of the type
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<varname>After=</varname> for this target unit to all
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services (except for those with
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<varname>DefaultDependencies=no</varname>).</para>
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<para>Usually, this should pull-in all local mount points plus
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<filename>/var/</filename>, <filename>/tmp/</filename> and
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<filename>/var/tmp/</filename>, swap devices, sockets, timers,
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path units and other basic initialization necessary for general
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purpose daemons. The mentioned mount points are special cased
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to allow them to be remote.
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</para>
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<para>This target usually does not pull in any non-target units
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directly, but rather does so indirectly via other early boot targets.
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It is instead meant as a synchronization point for late boot
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services. Refer to
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<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for details on the targets involved.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>boot-complete.target</filename></term>
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<listitem>
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<para>This target is intended as generic synchronization point for services that shall determine or act on
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whether the boot process completed successfully. Order units that are required to succeed for a boot process
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to be considered successful before this unit, and add a <varname>Requires=</varname> dependency from the
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target unit to them. Order units that shall only run when the boot process is considered successful after the
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target unit and pull in the target from it, also with <varname>Requires=</varname>. Note that by default this
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target unit is not part of the initial boot transaction, but is supposed to be pulled in only if required by
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units that want to run only on successful boots.</para>
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<para>See
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<citerefentry><refentrytitle>systemd-boot-check-no-failures.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for a service that implements a generic system health check and orders itself before
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<filename>boot-complete.target</filename>.</para>
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<para>See
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<citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for a service that propagates boot success information to the boot loader, and orders itself after
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<filename>boot-complete.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>ctrl-alt-del.target</filename></term>
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<listitem>
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<para>systemd starts this target whenever Control+Alt+Del is
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pressed on the console. Usually, this should be aliased
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(symlinked) to <filename>reboot.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>cryptsetup.target</filename></term>
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<listitem>
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<para>A target that pulls in setup services for all
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encrypted block devices.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>veritysetup.target</filename></term>
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<listitem>
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<para>A target that pulls in setup services for all
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verity integrity protected block devices.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>dbus.service</filename></term>
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<listitem>
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<para>A special unit for the D-Bus bus daemon. As soon as
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this service is fully started up systemd will connect to it
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and register its service.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>dbus.socket</filename></term>
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<listitem>
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<para>A special unit for the D-Bus system bus socket. All
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units with <varname>Type=dbus</varname> automatically gain a
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dependency on this unit.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>default.target</filename></term>
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<listitem>
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<para>The default unit systemd starts at bootup. Usually, this should be aliased (symlinked) to
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<filename>multi-user.target</filename> or <filename>graphical.target</filename>. See
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<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
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more discussion.</para>
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<para>The default unit systemd starts at bootup can be overridden with the
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<varname>systemd.unit=</varname> kernel command line option, or more conveniently, with the short
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names like <varname>single</varname>, <varname>rescue</varname>, <varname>1</varname>,
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<varname>3</varname>, <varname>5</varname>, …; see
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>display-manager.service</filename></term>
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<listitem>
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<para>The display manager service. Usually, this should be
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aliased (symlinked) to <filename>gdm.service</filename> or a
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similar display manager service.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>emergency.target</filename></term>
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<listitem>
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<para>A special target unit that starts an emergency shell on the main console. This
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target does not pull in other services or mounts. It is the most minimal version of
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starting the system in order to acquire an interactive shell; the only processes running
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are usually just the system manager (PID 1) and the shell process. This unit may be used
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by specifying <varname>emergency</varname> on the kernel command line; it is
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also used when a file system check on a required file system fails and boot-up cannot
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continue. Compare with <filename>rescue.target</filename>, which serves a similar
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purpose, but also starts the most basic services and mounts all file systems.</para>
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<para>In many ways booting into <filename>emergency.target</filename> is similar to the
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effect of booting with <literal>init=/bin/sh</literal> on the kernel command line,
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except that emergency mode provides you with the full system and service manager, and
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allows starting individual units in order to continue the boot process in steps.</para>
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<para>Note that depending on how <filename>emergency.target</filename> is reached, the root file
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system might be mounted read-only or read-write (no remounting is done specially for this
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target). For example, the system may boot with root mounted read-only when <varname>ro</varname>
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is used on the kernel command line and remain this way for <filename>emergency.target</filename>,
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or the system may transition to <filename>emergency.target</filename> after the system has been
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partially booted and disks have already been remounted read-write.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>exit.target</filename></term>
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<listitem>
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<para>A special service unit for shutting down the system or
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user service manager. It is equivalent to
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<filename>poweroff.target</filename> on non-container
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systems, and also works in containers.</para>
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<para>systemd will start this unit when it receives the
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<constant>SIGTERM</constant> or <constant>SIGINT</constant>
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signal when running as user service daemon.</para>
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<para>Normally, this (indirectly) pulls in
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<filename>shutdown.target</filename>, which in turn should be
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conflicted by all units that want to be scheduled for
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shutdown when the service manager starts to exit.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>factory-reset.target</filename></term>
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<listitem>
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<para>A special target to trigger a factory reset.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>final.target</filename></term>
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<listitem>
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<para>A special target unit that is used during the shutdown
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logic and may be used to pull in late services after all
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normal services are already terminated and all mounts
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unmounted.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>getty.target</filename></term>
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<listitem>
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<para>A special target unit that pulls in statically
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configured local TTY <filename>getty</filename> instances.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>graphical.target</filename></term>
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<listitem>
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<para>A special target unit for setting up a graphical login
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screen. This pulls in
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<filename>multi-user.target</filename>.</para>
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<para>Units that are needed for graphical logins shall add
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<varname>Wants=</varname> dependencies for their unit to
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this unit (or <filename>multi-user.target</filename>) during
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installation. This is best configured via
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<varname>WantedBy=graphical.target</varname> in the unit's
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[Install] section.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>hibernate.target</filename></term>
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<listitem>
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<para>A special target unit for hibernating the system. This
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pulls in <filename>sleep.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>hybrid-sleep.target</filename></term>
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<listitem>
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<para>A special target unit for hibernating and suspending
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the system at the same time. This pulls in
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<filename>sleep.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>suspend-then-hibernate.target</filename></term>
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<listitem>
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<para>A special target unit for suspending the system for a period
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of time, waking it and putting it into hibernate. This pulls in
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<filename>sleep.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>halt.target</filename></term>
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<listitem>
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<para>A special target unit for shutting down and halting
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the system. Note that this target is distinct from
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<filename>poweroff.target</filename> in that it generally
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really just halts the system rather than powering it
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down.</para>
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<para>Applications wanting to halt the system should not start this unit
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directly, but should instead execute <command>systemctl halt</command>
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(possibly with the <option>--no-block</option> option) or call
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>org.freedesktop.systemd1.Manager.Halt</command> D-Bus method
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directly.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>init.scope</filename></term>
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<listitem>
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<para>This scope unit is where the system and service manager (PID 1) itself resides. It
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is active as long as the system is running.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>initrd.target</filename></term>
|
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<listitem>
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<para>This is the default target in the initramfs, similar to <filename>default.target</filename>
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in the main system. It is used to mount the real root and transition to it. See
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<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
|
|
more discussion.</para>
|
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</listitem>
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</varlistentry>
|
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<varlistentry>
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<term><filename>initrd-fs.target</filename></term>
|
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<listitem>
|
|
<para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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automatically adds dependencies of type <varname>Before=</varname> to
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<filename>sysroot-usr.mount</filename> and all mount points found in
|
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<filename>/etc/fstab</filename> that have the <option>x-initrd.mount</option> mount option set
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|
and do not have the <option>noauto</option> mount option set. It is also indirectly ordered after
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<filename>sysroot.mount</filename>. Thus, once this target is reached the
|
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<filename>/sysroot/</filename> hierarchy is fully set up, in preparation for the transition to
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the host OS.</para>
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</listitem>
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</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>initrd-root-device.target</filename></term>
|
|
<listitem>
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<para>A special initrd target unit that is reached when the root filesystem device is available, but before
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it has been mounted.
|
|
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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|
and
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|
<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
automatically setup the appropriate dependencies to make this happen.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>initrd-root-fs.target</filename></term>
|
|
<listitem>
|
|
<para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
automatically adds dependencies of type <varname>Before=</varname> to the
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<filename>sysroot.mount</filename> unit, which is generated from the kernel command line's
|
|
<varname>root=</varname> setting (or equivalent).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>initrd-usr-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
|
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<filename>sysusr-usr.mount</filename> unit, which is generated from the kernel command line's
|
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<varname>usr=</varname> switch. Services may order themselves after this target unit in order to
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|
run once the <filename>/sysusr/</filename> hierarchy becomes available, on systems that come up
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|
initially without a root file system, but with an initialized <filename>/usr/</filename> and need
|
|
to access that before setting up the root file system to ultimately switch to. On systems where
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<varname>usr=</varname> is not used this target is ordered after
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|
<filename>sysroot.mount</filename> and thus mostly equivalent to
|
|
<filename>initrd-root-fs.target</filename>. In effect on any system once this target is reached
|
|
the file system backing <filename>/usr/</filename> is mounted, though possibly at two different
|
|
locations, either below the <filename>/sysusr/</filename> or the <filename>/sysroot/</filename>
|
|
hierarchies.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>kbrequest.target</filename></term>
|
|
<listitem>
|
|
<para>systemd starts this target whenever Alt+ArrowUp is
|
|
pressed on the console. Note that any user with physical access
|
|
to the machine will be able to do this, without authentication,
|
|
so this should be used carefully.</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 should not start this unit
|
|
directly, but should instead execute <command>systemctl kexec</command>
|
|
(possibly with the <option>--no-block</option> option) or call
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
|
|
<command>org.freedesktop.systemd1.Manager.KExec</command> D-Bus method
|
|
directly.</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>machines.target</filename></term>
|
|
<listitem>
|
|
<para>A standard target unit for starting all the containers
|
|
and other virtual machines. See <filename>systemd-nspawn@.service</filename>
|
|
for an example.</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
|
|
[Install] 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="https://systemd.io/NETWORK_ONLINE">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 <emphasis>provide</emphasis>
|
|
functionality to other hosts (as opposed to <emphasis>consume</emphasis> functionality of other
|
|
hosts) generally do not need to pull this in.</para>
|
|
|
|
<para>systemd automatically adds dependencies of type <varname>Wants=</varname> and
|
|
<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>
|
|
|
|
<para>Note that this unit is only useful during the original system start-up
|
|
logic. After the system has completed booting up, it will not track the online state of
|
|
the system anymore. Due to this it cannot be used as a network connection monitor
|
|
concept, it is purely a one-time system start-up concept.</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
|
|
[Install] 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 not start this unit
|
|
directly, but should instead execute <command>systemctl poweroff</command>
|
|
(possibly with the <option>--no-block</option> option) or call
|
|
<citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
|
|
<command>org.freedesktop.login1.Manager.PowerOff</command> D-Bus method
|
|
directly.</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 not start this unit
|
|
directly, but should instead execute <command>systemctl reboot</command>
|
|
(possibly with the <option>--no-block</option> option) or call
|
|
<citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
|
|
<command>org.freedesktop.login1.Manager.Reboot</command> D-Bus method
|
|
directly.</para>
|
|
|
|
<para><filename>runlevel6.target</filename> is an alias for
|
|
this target unit, for compatibility with SysV.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-cryptsetup.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>cryptsetup.target</filename>, but for encrypted
|
|
devices which are accessed over the network. It is used for
|
|
<citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
entries marked with <option>_netdev</option>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-veritysetup.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>veritysetup.target</filename>, but for verity
|
|
integrity protected devices which are accessed over the network. It is used for
|
|
<citerefentry><refentrytitle>veritytab</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
entries marked with <option>_netdev</option>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-fs.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>local-fs.target</filename>, but
|
|
for remote mount points.</para>
|
|
|
|
<para>systemd automatically adds dependencies of type
|
|
<varname>After=</varname> for this target unit to all SysV
|
|
init script service units with an LSB header referring to
|
|
the <literal>$remote_fs</literal> facility.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>rescue.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that pulls in the base system (including system mounts) and
|
|
spawns a rescue shell. Isolate to this target in order to administer the system in
|
|
single-user mode with all file systems mounted but with no services running, except for
|
|
the most basic. Compare with <filename>emergency.target</filename>, which is much more
|
|
reduced and does not provide the file systems or most basic services. Compare with
|
|
<filename>multi-user.target</filename>, this target could be seen as
|
|
<filename>single-user.target</filename>.</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>runlevel2.target</filename></term>
|
|
<term><filename>runlevel3.target</filename></term>
|
|
<term><filename>runlevel4.target</filename></term>
|
|
<term><filename>runlevel5.target</filename></term>
|
|
<listitem>
|
|
<para>These are targets that are called whenever the SysV
|
|
compatibility code asks for runlevel 2, 3, 4, 5,
|
|
respectively. It is a good idea to make this an alias for
|
|
(i.e. symlink to) <filename>graphical.target</filename>
|
|
(for runlevel 5) or <filename>multi-user.target</filename>
|
|
(the others).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>shutdown.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that terminates the services on
|
|
system shutdown.</para>
|
|
|
|
<para>Services that shall be terminated on system shutdown
|
|
shall add <varname>Conflicts=</varname> and
|
|
<varname>Before=</varname> dependencies to this unit for
|
|
their service unit, which is implicitly done when
|
|
<varname>DefaultDependencies=yes</varname> is set (the
|
|
default).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sigpwr.target</filename></term>
|
|
<listitem>
|
|
<para>A special target that is started when systemd receives
|
|
the SIGPWR process signal, which is normally sent by the
|
|
kernel or UPS daemons when power fails.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sleep.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that is pulled in by
|
|
<filename>suspend.target</filename>,
|
|
<filename>hibernate.target</filename> and
|
|
<filename>hybrid-sleep.target</filename> and may be used to
|
|
hook units into the sleep state logic.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>slices.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that sets up all slice units (see
|
|
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
for details) that shall always be active after boot. By default the generic
|
|
<filename>system.slice</filename> slice unit as well as the root slice unit
|
|
<filename>-.slice</filename> are pulled in and ordered before this unit (see
|
|
below).</para>
|
|
|
|
<para>Adding slice units to <filename>slices.target</filename> is generally not
|
|
necessary. Instead, when some unit that uses <varname>Slice=</varname> is started, the
|
|
specified slice will be started automatically. Adding
|
|
<varname>WantedBy=slices.target</varname> lines to the [Install]
|
|
section should only be done for units that need to be always active. In that case care
|
|
needs to be taken to avoid creating a loop through the automatic dependencies on
|
|
"parent" slices.</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 [Install]
|
|
section.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>suspend.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit for suspending the system. This
|
|
pulls in <filename>sleep.target</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>swap.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>local-fs.target</filename>, but
|
|
for swap partitions and swap files.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sysinit.target</filename></term>
|
|
<listitem>
|
|
<para>systemd automatically adds dependencies of the types
|
|
<varname>Requires=</varname> and <varname>After=</varname>
|
|
for this target unit to all services (except for those with
|
|
<varname>DefaultDependencies=no</varname>).</para>
|
|
|
|
<para>This target pulls in the services required for system
|
|
initialization. System services pulled in by this target should
|
|
declare <varname>DefaultDependencies=no</varname> and specify
|
|
all their dependencies manually, including access to anything
|
|
more than a read only root filesystem. For details on the
|
|
dependencies of this target, refer to
|
|
<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>syslog.socket</filename></term>
|
|
<listitem>
|
|
<para>The socket unit syslog implementations should listen
|
|
on. All userspace log messages will be made available on
|
|
this socket. For more information about syslog integration,
|
|
please consult the <ulink
|
|
url="https://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
|
|
Interface</ulink> document.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>system-update.target</filename></term>
|
|
<term><filename>system-update-pre.target</filename></term>
|
|
<term><filename>system-update-cleanup.service</filename></term>
|
|
<listitem>
|
|
<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
|
|
<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. The
|
|
main units executing the update should order themselves after
|
|
<filename>system-update-pre.target</filename> but not pull it in. Services which want to
|
|
run during system updates only, but before the actual system update is executed should
|
|
order themselves before this unit and pull it in. As a safety measure, if this does not
|
|
happen, and <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>
|
|
<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 [Install] section.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>umount.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that unmounts all mount and
|
|
automount points on system shutdown.</para>
|
|
|
|
<para>Mounts that shall be unmounted on system shutdown
|
|
shall add Conflicts dependencies to this unit for their
|
|
mount unit, which is implicitly done when
|
|
<varname>DefaultDependencies=yes</varname> is set (the
|
|
default).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<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>
|
|
<varlistentry>
|
|
<term><filename>usb-gadget.target</filename></term>
|
|
<listitem>
|
|
<para>This target is started automatically as soon as a
|
|
USB Device Controller becomes available at boot.</para>
|
|
|
|
<para>This may be used to pull in usb gadget
|
|
dynamically when UDC hardware is found.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<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>blockdev@.target</filename></term>
|
|
<listitem><para>This template unit is used to order mount units and other consumers of block
|
|
devices after services that synthesize these block devices. In particular, this is intended to be
|
|
used with storage services (such as
|
|
<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>/
|
|
<citerefentry><refentrytitle>systemd-veritysetup@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
|
|
that allocate and manage a virtual block device. Storage services are ordered before an instance of
|
|
<filename>blockdev@.target</filename>, and the consumer units after it. The ordering is
|
|
particularly relevant during shutdown, as it ensures that the mount is deactivated first and the
|
|
service backing the mount later. The <filename>blockdev@.target</filename> instance should be
|
|
pulled in via a <option>Wants=</option> dependency of the storage daemon and thus generally not be
|
|
part of any transaction unless a storage daemon is used. The instance name for instances of this
|
|
template unit must be a properly escaped block device node path, e.g.
|
|
<filename index="false">blockdev@dev-mapper-foobar.target</filename> for the storage device
|
|
<filename index="false">/dev/mapper/foobar</filename>.</para></listitem>
|
|
</varlistentry>
|
|
<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>veritysetup-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This passive target unit may be pulled in by services
|
|
that want to run before any verity integrity protected block
|
|
device is set up. All verity integrity protected 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 verity integrity
|
|
protected block devices are fully stopped.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>first-boot-complete.target</filename></term>
|
|
<listitem>
|
|
<para>This passive target is intended as a synchronization point for units that need to run once
|
|
during the first boot. Only after all units ordered before this target have finished, will the
|
|
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
be committed to disk, marking the first boot as completed. If the boot is aborted at any time
|
|
before that, the next boot will re-run any units with <varname>ConditionFirstBoot=yes</varname>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>getty-pre.target</filename></term>
|
|
<listitem>
|
|
<para>A special passive target unit. Users of this target
|
|
are expected to pull it in the boot transaction via
|
|
a dependency (e.g. <varname>Wants=</varname>). Order your
|
|
unit before this unit if you want to make use of the console
|
|
just before <filename>getty</filename> is started.
|
|
</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. However, the following should apply at
|
|
minimum:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem><para>At start-up, any configured synthetic network devices (i.e. not physical ones
|
|
that require hardware to show up and be probed, but virtual ones like bridge devices and
|
|
similar which are created programmatically) that do not depend on any underlying hardware
|
|
should be allocated by the time this target is reached. It is not necessary for these
|
|
interfaces to also have completed IP level configuration by the time
|
|
<filename>network.target</filename> is reached.</para></listitem>
|
|
|
|
<listitem><para>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 by 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="https://systemd.io/NETWORK_ONLINE">Running Services After the Network Is Up</ulink> for
|
|
more information.</para></listitem>
|
|
</itemizedlist>
|
|
|
|
<para>It must emphasized that at start-up there's no guarantee that hardware-based devices have
|
|
shown up by the time this target is reached, or even acquired complete IP configuration. For that
|
|
purpose use <filename>network-online.target</filename> as described above.</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. Also see <ulink
|
|
url="https://systemd.io/NETWORK_ONLINE">Running Services After the Network Is Up</ulink> for more
|
|
information.</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 UNIX 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 regular UNIX
|
|
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. All services which provide parts of the
|
|
user/group database should be ordered before this target, and pull it in. Note that this
|
|
unit is only relevant for regular users and groups — system users and groups are
|
|
required to be resolvable during earliest boot already, and hence do not need any
|
|
special ordering against this target.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-fs-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This target unit is automatically ordered before all
|
|
mount point units (see above) and cryptsetup/veritysetup devices
|
|
marked with the <option>_netdev</option>. It can be used to run
|
|
certain units before remote encrypted devices and mounts are established.
|
|
Note that this unit is generally not part of the initial
|
|
transaction, unless the unit that wants to be ordered before
|
|
all remote mounts pulls it in via a
|
|
<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-set.target</filename></term>
|
|
<listitem>
|
|
<para>Services responsible for setting the system clock (<constant>CLOCK_REALTIME</constant>)
|
|
from a local source (such as a maintained timestamp file or imprecise real-time clock) should
|
|
pull in this target and order themselves before it. Services where approximate, roughly monotonic
|
|
time is desired should be ordered after this unit, but not pull it in.</para>
|
|
|
|
<para>This target does not provide the accuracy guarantees of
|
|
<filename>time-sync.target</filename> (see below), however does not depend on remote clock
|
|
sources to be reachable, i.e. the target is typically not delayed by network problems and
|
|
similar. Use of this target is recommended for services where approximate clock accuracy and
|
|
rough monotonicity is desired but activation shall not be delayed for possibly unreliable network
|
|
communication.</para>
|
|
|
|
<para>The service manager automatically adds dependencies of type <varname>After=</varname> for
|
|
this target unit to all timer units with at least one <varname>OnCalendar=</varname>
|
|
directive.</para>
|
|
|
|
<para>The
|
|
<citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
service is a simple daemon that pulls in this target and orders itself before it. Besides
|
|
implementing the SNTP network protocol it maintains a timestamp file on disk whose modification
|
|
time is regularlary updated. At service start-up the local system clock is set from that modification time,
|
|
ensuring it increases roughly monotonically.</para>
|
|
|
|
<para>Note that ordering a unit after <filename>time-set.target</filename> only has effect if
|
|
there's actually a service ordered before it that delays it until the clock is adjusted for rough
|
|
monotonicity. Otherwise, this target might get reached before the clock is adjusted to be roughly
|
|
monotonic. Enable
|
|
<citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
|
or an alternative NTP implementation to delay the target.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>time-sync.target</filename></term>
|
|
<listitem>
|
|
<para>Services indicating completed synchronization of the system clock
|
|
(<constant>CLOCK_REALTIME</constant>) to a remote source should pull in this target and order
|
|
themselves before it. Services where accurate time is essential should be ordered after this
|
|
unit, but not pull it in.</para>
|
|
|
|
<para>The service manager 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, as well to all timer units with at least one
|
|
<varname>OnCalendar=</varname> directive.</para>
|
|
|
|
<para>This target provides stricter clock accuracy guarantees than
|
|
<filename>time-set.target</filename> (see above), but likely requires
|
|
network communication and thus introduces unpredictable delays.
|
|
Services that require clock accuracy and where network
|
|
communication delays are acceptable should use this target. Services that require a less accurate
|
|
clock, and only approximate and roughly monotonic clock behaviour should use
|
|
<filename>time-set.target</filename> instead.</para>
|
|
|
|
<para>Note that ordering a unit after <filename>time-sync.target</filename> only has effect if
|
|
there's actually a service ordered before it that delays it until clock synchronization is
|
|
reached. Otherwise, this target might get reached before the clock is synchronized to any remote
|
|
accurate reference clock. When using
|
|
<citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
|
enable
|
|
<citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
to delay the target; or use an equivalent service for other NTP implementations.</para>
|
|
|
|
<table>
|
|
<title>Comparison</title>
|
|
<tgroup cols='2' align='left' colsep='1' rowsep='1'>
|
|
<colspec colname="time-set" />
|
|
<colspec colname="time-sync" />
|
|
<thead>
|
|
<row>
|
|
<entry><filename>time-set.target</filename></entry>
|
|
<entry><filename>time-sync.target</filename></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>"quick" to reach</entry>
|
|
<entry>"slow" to reach</entry>
|
|
</row>
|
|
<row>
|
|
<entry>typically uses local clock sources, boot process not affected by availability of external resources</entry>
|
|
<entry>typically uses remote clock sources, inserts dependencies on remote resources into boot process</entry>
|
|
</row>
|
|
<row>
|
|
<entry>reliable, because local</entry>
|
|
<entry>unreliable, because typically network involved</entry>
|
|
</row>
|
|
<row>
|
|
<entry>typically guarantees an approximate and roughly monotonic clock only</entry>
|
|
<entry>typically guarantees an accurate clock</entry>
|
|
</row>
|
|
<row>
|
|
<entry>implemented by <filename>systemd-timesyncd.service</filename></entry>
|
|
<entry>implemented by <filename>systemd-time-wait-sync.service</filename></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<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. See
|
|
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
|
for details about slice units.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>-.slice</filename></term>
|
|
<listitem>
|
|
<para>The root slice is the root of the slice hierarchy. It usually does not contain
|
|
units directly, but may be used to set defaults for the whole tree.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>system.slice</filename></term>
|
|
<listitem>
|
|
<para>By default, all system services started by
|
|
<command>systemd</command> are found in this slice.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>user.slice</filename></term>
|
|
<listitem>
|
|
<para>By default, all user processes and services started on
|
|
behalf of the user, including the per-user systemd instance
|
|
are found in this slice. This is pulled in by
|
|
<filename>systemd-logind.service</filename>.</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. This is pulled in by
|
|
<filename>systemd-machined.service</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Units managed by the user service manager</title>
|
|
|
|
<refsect2>
|
|
<title>Special User Units</title>
|
|
|
|
<para>When systemd runs as a user instance, the following special
|
|
units are available:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>default.target</filename></term>
|
|
<listitem>
|
|
<para>This is the main target of the user session, started by default. Various services that
|
|
compose the normal user session should be pulled into this target. In this regard,
|
|
<filename>default.target</filename> is similar to <filename>multi-user.target</filename> in the
|
|
system instance, but it is a real unit, not an alias.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>In addition, the following units are available which have definitions similar to their
|
|
system counterparts:
|
|
<filename>exit.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>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<title>Special Passive User Units</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>graphical-session.target</filename></term>
|
|
<listitem>
|
|
<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 [Unit]
|
|
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>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>graphical-session-pre.target</filename></term>
|
|
<listitem>
|
|
<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>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>xdg-desktop-autostart.target</filename></term>
|
|
<listitem>
|
|
<para>The XDG specification defines a way to autostart applications using XDG desktop files.
|
|
systemd ships
|
|
<citerefentry><refentrytitle>systemd-xdg-autostart-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
for the XDG desktop files in autostart directories. Desktop Environments can opt-in to use this
|
|
service by adding a <varname>Wants=</varname> dependency on
|
|
<filename>xdg-desktop-autostart.target</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<title>Special User Slice Units</title>
|
|
|
|
<para>There are four <literal>.slice</literal> units which form the basis of the user hierarchy for
|
|
assignment of resources for user applications and services. See
|
|
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
|
for details about slice units and the documentation about
|
|
<ulink url="https://systemd.io/DESKTOP_ENVIRONMENTS">Desktop Environments</ulink>
|
|
for further information.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>-.slice</filename></term>
|
|
<listitem>
|
|
<para>The root slice is the root of the user's slice 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>app.slice</filename></term>
|
|
<listitem>
|
|
<para>By default, all user services and applications managed by
|
|
<command>systemd</command> are found in this slice.
|
|
All interactively launched applications like web browsers and text editors
|
|
as well as non-critical services should be placed into this slice.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>session.slice</filename></term>
|
|
<listitem>
|
|
<para>All essential services and applications required for the
|
|
session should use this slice.
|
|
These are services that either cannot be restarted easily
|
|
or where latency issues may affect the interactivity of the system and applications.
|
|
This includes the display server, screen readers and other services such as DBus or XDG portals.
|
|
Such services should be configured to be part of this slice by
|
|
adding <varname>Slice=session.slice</varname> to their unit files.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>background.slice</filename></term>
|
|
<listitem>
|
|
<para>All services running low-priority background tasks should use this slice.
|
|
This permits resources to be preferentially assigned to the other slices.
|
|
Examples include non-interactive tasks like file indexing or backup operations
|
|
where latency is not important.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</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><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>user@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|