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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
9 | <refentry id="systemd-halt.service"> | |
10 | ||
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11 | <refentryinfo> |
12 | <title>systemd-halt.service</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>systemd-halt.service</refentrytitle> | |
18 | <manvolnum>8</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>systemd-halt.service</refname> | |
23 | <refname>systemd-poweroff.service</refname> | |
24 | <refname>systemd-reboot.service</refname> | |
25 | <refname>systemd-kexec.service</refname> | |
26 | <refname>systemd-shutdown</refname> | |
27 | <refpurpose>System shutdown logic</refpurpose> | |
28 | </refnamediv> | |
29 | ||
30 | <refsynopsisdiv> | |
31 | <para><filename>systemd-halt.service</filename></para> | |
32 | <para><filename>systemd-poweroff.service</filename></para> | |
33 | <para><filename>systemd-reboot.service</filename></para> | |
34 | <para><filename>systemd-kexec.service</filename></para> | |
12b42c76 | 35 | <para><filename>/usr/lib/systemd/systemd-shutdown</filename></para> |
7fbbf283 | 36 | <para><filename>/usr/lib/systemd/system-shutdown/</filename></para> |
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37 | </refsynopsisdiv> |
38 | ||
39 | <refsect1> | |
40 | <title>Description</title> | |
41 | ||
42 | <para><filename>systemd-halt.service</filename> is a system | |
43 | service that is pulled in by <filename>halt.target</filename> and | |
44 | is responsible for the actual system halt. Similarly, | |
45 | <filename>systemd-poweroff.service</filename> is pulled in by | |
46 | <filename>poweroff.target</filename>, | |
47 | <filename>systemd-reboot.service</filename> by | |
48 | <filename>reboot.target</filename> and | |
49 | <filename>systemd-kexec.service</filename> by | |
50 | <filename>kexec.target</filename> to execute the respective | |
51 | actions.</para> | |
52 | ||
53 | <para>When these services are run, they ensure that PID 1 is | |
54 | replaced by the | |
12b42c76 | 55 | <filename>/usr/lib/systemd/systemd-shutdown</filename> tool which |
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56 | is then responsible for the actual shutdown. Before shutting down, |
57 | this binary will try to unmount all remaining file systems, | |
58 | disable all remaining swap devices, detach all remaining storage | |
59 | devices and kill all remaining processes.</para> | |
60 | ||
61 | <para>It is necessary to have this code in a separate binary | |
62 | because otherwise rebooting after an upgrade might be broken — the | |
63 | running PID 1 could still depend on libraries which are not | |
64 | available any more, thus keeping the file system busy, which then | |
65 | cannot be re-mounted read-only.</para> | |
66 | ||
67 | <para>Immediately before executing the actual system | |
68 | halt/poweroff/reboot/kexec <filename>systemd-shutdown</filename> | |
69 | will run all executables in | |
12b42c76 | 70 | <filename>/usr/lib/systemd/system-shutdown/</filename> and pass |
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71 | one arguments to them: either <literal>halt</literal>, |
72 | <literal>poweroff</literal>, <literal>reboot</literal> or | |
73 | <literal>kexec</literal>, depending on the chosen action. All | |
74 | executables in this directory are executed in parallel, and | |
75 | execution of the action is not continued before all executables | |
76 | finished.</para> | |
77 | ||
78 | <para>Note that <filename>systemd-halt.service</filename> (and the | |
79 | related units) should never be executed directly. Instead, trigger | |
80 | system shutdown with a command such as <literal>systemctl | |
81 | halt</literal> or suchlike.</para> | |
82 | </refsect1> | |
83 | ||
84 | <refsect1> | |
85 | <title>See Also</title> | |
86 | <para> | |
87 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
88 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
89 | <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
90 | <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
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91 | <citerefentry><refentrytitle>systemd-suspend.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
92 | <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
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93 | </para> |
94 | </refsect1> | |
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95 | |
96 | </refentry> |