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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="systemd-halt.service">
+
+ <refentryinfo>
+ <title>systemd-halt.service</title>
+ <productname>systemd</productname>
+ </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>
+ <para><filename>/usr/lib/systemd/system-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>,
+ <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>