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nspawn,man: use a common vocabulary when referring to selinux security contexts
[elogind.git] / man / systemd-halt.service.xml
1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4
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8   Copyright 2012 Lennart Poettering
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23
24 <refentry id="systemd-halt.service">
25
26         <refentryinfo>
27                 <title>systemd-halt.service</title>
28                 <productname>systemd</productname>
29
30                 <authorgroup>
31                         <author>
32                                 <contrib>Developer</contrib>
33                                 <firstname>Lennart</firstname>
34                                 <surname>Poettering</surname>
35                                 <email>lennart@poettering.net</email>
36                         </author>
37                 </authorgroup>
38         </refentryinfo>
39
40         <refmeta>
41                 <refentrytitle>systemd-halt.service</refentrytitle>
42                 <manvolnum>8</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>systemd-halt.service</refname>
47                 <refname>systemd-poweroff.service</refname>
48                 <refname>systemd-reboot.service</refname>
49                 <refname>systemd-kexec.service</refname>
50                 <refname>systemd-shutdown</refname>
51                 <refpurpose>System shutdown logic</refpurpose>
52         </refnamediv>
53
54         <refsynopsisdiv>
55                 <para><filename>systemd-halt.service</filename></para>
56                 <para><filename>systemd-poweroff.service</filename></para>
57                 <para><filename>systemd-reboot.service</filename></para>
58                 <para><filename>systemd-kexec.service</filename></para>
59                 <para><filename>/usr/lib/systemd/systemd-shutdown</filename></para>
60         </refsynopsisdiv>
61
62         <refsect1>
63                 <title>Description</title>
64
65                 <para><filename>systemd-halt.service</filename> is a
66                 system service that is pulled in by
67                 <filename>halt.target</filename> and is responsible
68                 for the actual system halt. Similarly,
69                 <filename>systemd-poweroff.service</filename> is
70                 pulled in by <filename>poweroff.target</filename>,
71                 <filename>systemd-reboot.service</filename> by
72                 <filename>reboot.target</filename> and
73                 <filename>systemd-kexec.service</filename> by
74                 <filename>kexec.target</filename> to execute the
75                 respective actions.</para>
76
77                 <para>When these services are run, they ensure that PID
78                 1 is replaced by the
79                 <filename>/usr/lib/systemd/systemd-shutdown</filename>
80                 tool which is then responsible for the actual
81                 shutdown. Before shutting down, this binary will try to
82                 unmount all remaining file systems, disable all
83                 remaining swap devices, detach all remaining storage
84                 devices and kill all remaining processes.</para>
85
86                 <para>It is necessary to have this code in a separate binary
87                 because otherwise rebooting after an upgrade might be broken —
88                 the running PID 1 could still depend on libraries which are not
89                 available any more, thus keeping the file system busy, which
90                 then cannot be re-mounted read-only.</para>
91
92                 <para>Immediately before executing the actual system
93                 halt/poweroff/reboot/kexec
94                 <filename>systemd-shutdown</filename> will run all
95                 executables in
96                 <filename>/usr/lib/systemd/system-shutdown/</filename>
97                 and pass one arguments to them: either
98                 <literal>halt</literal>,
99                 <literal>poweroff</literal>,
100                 <literal>reboot</literal> or
101                 <literal>kexec</literal>, depending on the chosen
102                 action. All executables in this directory are executed
103                 in parallel, and execution of the action is not
104                 continued before all executables finished.</para>
105
106                 <para>Note that
107                 <filename>systemd-halt.service</filename> (and the
108                 related units) should never be executed
109                 directly. Instead, trigger system shutdown with a
110                 command such as <literal>systemctl halt</literal> or
111                 suchlike.</para>
112         </refsect1>
113
114         <refsect1>
115                 <title>See Also</title>
116                 <para>
117                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
118                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
119                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
120                         <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
121                         <citerefentry><refentrytitle>systemd-suspend.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
122                 </para>
123         </refsect1>
124
125 </refentry>