systemd/man/systemd-machine-id-commit.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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<refentry id="systemd-machine-id-commit"
          xmlns:xi="http://www.w3.org/2001/XInclude">

        <refentryinfo>
                <title>systemd-machine-id-commit</title>
                <productname>systemd</productname>

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Didier</firstname>
                                <surname>Roche</surname>
                                <email>didrocks@ubuntu.com</email>
                        </author>
                </authorgroup>
        </refentryinfo>

        <refmeta>
                <refentrytitle>systemd-machine-id-commit</refentrytitle>
                <manvolnum>1</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>systemd-machine-id-commit</refname>
                <refpurpose>Commit transient machine ID to /etc/machine-id</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <cmdsynopsis>
                        <command>systemd-machine-id-commit</command>
                </cmdsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><command>systemd-machine-id-commit</command> may
                be used to write on disk any transient machine ID
                mounted as a temporary file system in
                <filename>/etc/machine-id</filename> at boot time. See
                <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                for more information about this file.</para>

                <para>This tool will execute no operation if
                <filename>/etc/machine-id</filename> doesn't contain any
                valid machine ID, isn't mounted as an independent temporary
			    file system, of <filename>/etc</filename> is read-only. If
                those conditions are met, it will then write current machine ID
                to disk and unmount the transient
                <filename>/etc/machine-id</filename> file in a race-free
                manner to ensure that this file is always valid for other
                processes.</para>

                <para>Note that the traditional way to initialize the machine
                ID in <filename>/etc/machine-id</filename> is to use
                <command>systemd-machine-id-setup</command> by system
                installer tools. You can also use
                <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                to initialize the machine ID on mounted (but not
                booted) system images.</para>
        </refsect1>

        <refsect1>
                <title>Options</title>

                <para>The following options are understood:</para>

                <variablelist>
                        <varlistentry>
                                <term><option>--root=<replaceable>root</replaceable></option></term>
                                <listitem><para>Takes a directory path
                                as an argument. All paths will be
                                prefixed with the given alternate
                                <replaceable>root</replaceable> path,
                                including config search paths.
                                </para></listitem>
                        </varlistentry>
                        <xi:include href="standard-options.xml" xpointer="help" />
                        <xi:include href="standard-options.xml" xpointer="version" />
                </variablelist>

        </refsect1>

        <refsect1>
                <title>Exit status</title>

                <para>On success, 0 is returned, a non-zero failure
                code otherwise.</para>
        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd-machine-id-commit.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>