126 lines
5.7 KiB
XML
126 lines
5.7 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd-halt.service">
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<refentryinfo>
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<title>systemd-halt.service</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-halt.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-halt.service</refname>
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<refname>systemd-poweroff.service</refname>
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<refname>systemd-reboot.service</refname>
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<refname>systemd-kexec.service</refname>
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<refname>systemd-shutdown</refname>
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<refpurpose>System shutdown logic</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-halt.service</filename></para>
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<para><filename>systemd-poweroff.service</filename></para>
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<para><filename>systemd-reboot.service</filename></para>
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<para><filename>systemd-kexec.service</filename></para>
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<para><filename>/usr/lib/systemd/systemd-shutdown</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-halt.service</filename> is a
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system service that is pulled in by
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<filename>halt.target</filename> and is responsible
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for the actual system halt. Similarly,
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<filename>systemd-poweroff.service</filename> is
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pulled in by <filename>poweroff.target</filename>,
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<filename>systemd-reboot.service</filename> by
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<filename>reboot.target</filename> and
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<filename>systemd-kexec.service</filename> by
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<filename>kexec.target</filename> to execute the
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respective actions.</para>
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<para>When these services are run, they ensure that PID
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1 is replaced by the
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<filename>/usr/lib/systemd/systemd-shutdown</filename>
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tool which is then responsible for the actual
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shutdown. Before shutting down, this binary will try to
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unmount all remaining file systems, disable all
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remaining swap devices, detach all remaining storage
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devices and kill all remaining processes.</para>
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<para>It is necessary to have this code in a separate binary
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because otherwise rebooting after an upgrade might be broken —
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the running PID 1 could still depend on libraries which are not
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available any more, thus keeping the file system busy, which
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then cannot be re-mounted read-only.</para>
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<para>Immediately before executing the actual system
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halt/poweroff/reboot/kexec
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<filename>systemd-shutdown</filename> will run all
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executables in
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<filename>/usr/lib/systemd/system-shutdown/</filename>
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and pass one arguments to them: either
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<literal>halt</literal>,
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<literal>poweroff</literal>,
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<literal>reboot</literal> or
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<literal>kexec</literal>, depending on the chosen
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action. All executables in this directory are executed
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in parallel, and execution of the action is not
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continued before all executables finished.</para>
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<para>Note that
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<filename>systemd-halt.service</filename> (and the
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related units) should never be executed
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directly. Instead, trigger system shutdown with a
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command such as <literal>systemctl halt</literal> or
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suchlike.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-suspend.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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