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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
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3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
4 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
f47781d8 | 5 | <!-- |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
b012e921 | 8 | Copyright © 2014 Didier Roche |
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9 | --> |
10 | <refentry id="systemd-machine-id-commit.service"> | |
11 | ||
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12 | <refentryinfo> |
13 | <title>systemd-machine-id-commit.service</title> | |
14 | <productname>systemd</productname> | |
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15 | </refentryinfo> |
16 | ||
17 | <refmeta> | |
18 | <refentrytitle>systemd-machine-id-commit.service</refentrytitle> | |
19 | <manvolnum>8</manvolnum> | |
20 | </refmeta> | |
21 | ||
22 | <refnamediv> | |
23 | <refname>systemd-machine-id-commit.service</refname> | |
db2df898 | 24 | <refpurpose>Commit a transient machine ID to disk</refpurpose> |
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25 | </refnamediv> |
26 | ||
27 | <refsynopsisdiv> | |
28 | <para><filename>systemd-machine-id-commit.service</filename></para> | |
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29 | </refsynopsisdiv> |
30 | ||
31 | <refsect1> | |
32 | <title>Description</title> | |
33 | ||
6300502b | 34 | <para><filename>systemd-machine-id-commit.service</filename> is an |
db2df898 | 35 | early boot service responsible for committing transient |
6300502b | 36 | <filename>/etc/machine-id</filename> files to a writable disk file |
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37 | system. See |
38 | <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
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39 | for more information about machine IDs.</para> |
40 | ||
41 | <para>This service is started after | |
42 | <filename>local-fs.target</filename> in case | |
43 | <filename>/etc/machine-id</filename> is a mount point of its own | |
44 | (usually from a memory file system such as | |
45 | <literal>tmpfs</literal>) and /etc is writable. The service will | |
46 | invoke <command>systemd-machine-id-setup --commit</command>, which | |
47 | writes the current transient machine ID to disk and unmount the | |
e735f4d4 | 48 | <filename>/etc/machine-id</filename> file in a race-free manner to |
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49 | ensure that file is always valid and accessible for other |
50 | processes. See | |
51 | <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
52 | for details.</para> | |
53 | ||
54 | <para>The main use case of this service are systems where | |
55 | <filename>/etc/machine-id</filename> is read-only and initially | |
db2df898 | 56 | not initialized. In this case, the system manager will generate a |
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57 | transient machine ID file on a memory file system, and mount it |
58 | over <filename>/etc/machine-id</filename>, during the early boot | |
59 | phase. This service is then invoked in a later boot phase, as soon | |
60 | as <filename>/etc</filename> has been remounted writable and the | |
61 | ID may thus be committed to disk to make it permanent.</para> | |
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62 | </refsect1> |
63 | ||
64 | <refsect1> | |
65 | <title>See Also</title> | |
66 | <para> | |
67 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
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68 | <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
69 | <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
70 | <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
71 | </para> | |
72 | </refsect1> | |
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73 | |
74 | </refentry> |