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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | <!-- | |
5 | This file is part of systemd. | |
6 | ||
7 | Copyright 2014 Didier Roche | |
8 | ||
9 | systemd is free software; you can redistribute it and/or modify it | |
10 | under the terms of the GNU Lesser General Public License as published by | |
11 | the Free Software Foundation; either version 2.1 of the License, or | |
12 | (at your option) any later version. | |
13 | ||
14 | systemd is distributed in the hope that it will be useful, but | |
15 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | Lesser General Public License for more details. | |
18 | ||
19 | You should have received a copy of the GNU Lesser General Public License | |
20 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
21 | --> | |
22 | <refentry id="systemd-machine-id-commit.service"> | |
23 | ||
e735f4d4 MP |
24 | <refentryinfo> |
25 | <title>systemd-machine-id-commit.service</title> | |
26 | <productname>systemd</productname> | |
27 | ||
28 | <authorgroup> | |
29 | <author> | |
30 | <contrib>Developer</contrib> | |
31 | <firstname>Didier</firstname> | |
32 | <surname>Roche</surname> | |
33 | <email>didrocks@ubuntu.com</email> | |
34 | </author> | |
35 | </authorgroup> | |
36 | </refentryinfo> | |
37 | ||
38 | <refmeta> | |
39 | <refentrytitle>systemd-machine-id-commit.service</refentrytitle> | |
40 | <manvolnum>8</manvolnum> | |
41 | </refmeta> | |
42 | ||
43 | <refnamediv> | |
44 | <refname>systemd-machine-id-commit.service</refname> | |
45 | <refpurpose>Commit transient machine-id to disk</refpurpose> | |
46 | </refnamediv> | |
47 | ||
48 | <refsynopsisdiv> | |
49 | <para><filename>systemd-machine-id-commit.service</filename></para> | |
50 | <para><filename>/usr/lib/systemd/systemd-machine-id-commit</filename></para> | |
51 | </refsynopsisdiv> | |
52 | ||
53 | <refsect1> | |
54 | <title>Description</title> | |
55 | ||
56 | <para><filename>systemd-machine-id-commit.service</filename> is a | |
57 | service responsible for committing any transient | |
58 | <filename>/etc/machine-id</filename> file to a writable file | |
59 | system. See | |
60 | <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
61 | for more information about this file.</para> | |
62 | ||
63 | <para>This service is started shortly after | |
64 | <filename>local-fs.target</filename> if | |
65 | <filename>/etc/machine-id</filename> is an independent mount point | |
66 | (probably a tmpfs one) and /etc is writable. | |
67 | <command>systemd-machine-id-commit</command> will then write | |
68 | current machine ID to disk and unmount the transient | |
69 | <filename>/etc/machine-id</filename> file in a race-free manner to | |
70 | ensure that file is always valid for other processes.</para> | |
71 | ||
72 | <para>Note that the traditional way to initialize the machine ID | |
73 | in <filename>/etc/machine-id</filename> is to use | |
74 | <command>systemd-machine-id-setup</command> by system installer | |
75 | tools. You can also use | |
76 | <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
77 | to initialize the machine ID on mounted (but not booted) system | |
78 | images. The main use case for that service is | |
79 | <filename>/etc/machine-id</filename> being an empty file at boot | |
80 | and initrd chaining to systemd giving it a read only file system | |
81 | that will be turned read-write later during the boot | |
82 | process.</para> | |
83 | ||
84 | <para>There is no consequence if that service fails other than a | |
85 | newer machine-id will be generated during next system boot. | |
86 | </para> | |
87 | </refsect1> | |
88 | ||
89 | <refsect1> | |
90 | <title>See Also</title> | |
91 | <para> | |
92 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
93 | <citerefentry><refentrytitle>systemd-machine-id-commit</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
94 | <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
95 | <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
96 | <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
97 | </para> | |
98 | </refsect1> | |
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99 | |
100 | </refentry> |