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75 lines
2.9 KiB
XML
75 lines
2.9 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1-or-later
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Copyright © 2014 Didier Roche
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-->
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<refentry id="systemd-machine-id-commit.service">
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<refentryinfo>
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<title>systemd-machine-id-commit.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-machine-id-commit.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-machine-id-commit.service</refname>
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<refpurpose>Commit a transient machine ID to disk</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-machine-id-commit.service</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-machine-id-commit.service</filename> is an
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early boot service responsible for committing transient
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<filename>/etc/machine-id</filename> files to a writable disk file
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system. See
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more information about machine IDs.</para>
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<para>This service is started after
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<filename>local-fs.target</filename> in case
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<filename>/etc/machine-id</filename> is a mount point of its own
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(usually from a memory file system such as
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<literal>tmpfs</literal>) and /etc is writable. The service will
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invoke <command>systemd-machine-id-setup --commit</command>, which
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writes the current transient machine ID to disk and unmount the
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<filename>/etc/machine-id</filename> file in a race-free manner to
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ensure that file is always valid and accessible for other
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processes. See
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<citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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for details.</para>
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<para>The main use case of this service are systems where
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<filename>/etc/machine-id</filename> is read-only and initially
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not initialized. In this case, the system manager will generate a
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transient machine ID file on a memory file system, and mount it
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over <filename>/etc/machine-id</filename>, during the early boot
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phase. This service is then invoked in a later boot phase, as soon
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as <filename>/etc/</filename> has been remounted writable and the
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ID may thus be committed to disk to make it permanent.</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>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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