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>