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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<refentry id="systemd-halt.service">

<refentryinfo>

<title>systemd-halt.service</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>Developer</contrib>

<firstname>Lennart</firstname>

<surname>Poettering</surname>

<email>lennart@poettering.net</email>

</author>

</authorgroup>

</refentryinfo>

<refmeta>

<refentrytitle>systemd-halt.service</refentrytitle>

<manvolnum>8</manvolnum>

</refmeta>

<refnamediv>

<refname>systemd-halt.service</refname>

<refname>systemd-poweroff.service</refname>

<refname>systemd-reboot.service</refname>

<refname>systemd-kexec.service</refname>

<refname>systemd-shutdown</refname>

<refpurpose>System shutdown logic</refpurpose>

</refnamediv>

<refsynopsisdiv>

<para><filename>systemd-halt.service</filename></para>

<para><filename>systemd-poweroff.service</filename></para>

<para><filename>systemd-reboot.service</filename></para>

<para><filename>systemd-kexec.service</filename></para>

<para><filename>/usr/lib/systemd/systemd-shutdown</filename></para>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><filename>systemd-halt.service</filename> is a system

service that is pulled in by <filename>halt.target</filename> and

is responsible for the actual system halt. Similarly,

<filename>systemd-poweroff.service</filename> is pulled in by

<filename>poweroff.target</filename>,

<filename>systemd-reboot.service</filename> by

<filename>reboot.target</filename> and

<filename>systemd-kexec.service</filename> by

<filename>kexec.target</filename> to execute the respective

actions.</para>

<para>When these services are run, they ensure that PID 1 is

replaced by the

<filename>/usr/lib/systemd/systemd-shutdown</filename> tool which

is then responsible for the actual shutdown. Before shutting down,

this binary will try to unmount all remaining file systems,

disable all remaining swap devices, detach all remaining storage

devices and kill all remaining processes.</para>

<para>It is necessary to have this code in a separate binary

because otherwise rebooting after an upgrade might be broken — the

running PID 1 could still depend on libraries which are not

available any more, thus keeping the file system busy, which then

cannot be re-mounted read-only.</para>

<para>Immediately before executing the actual system

halt/poweroff/reboot/kexec <filename>systemd-shutdown</filename>

will run all executables in

<filename>/usr/lib/systemd/system-shutdown/</filename> and pass

one arguments to them: either <literal>halt</literal>,

<literal>poweroff</literal>, <literal>reboot</literal> or

<literal>kexec</literal>, depending on the chosen action. All

executables in this directory are executed in parallel, and

execution of the action is not continued before all executables

finished.</para>

<para>Note that <filename>systemd-halt.service</filename> (and the

related units) should never be executed directly. Instead, trigger

system shutdown with a command such as <literal>systemctl

halt</literal> or suchlike.</para>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,

<citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd-suspend.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>