<?xml version='1.0'?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2012 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <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>