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+<?xml version="1.0"?>
+<!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!--
+ This file is part of systemd.
+
+ Copyright 2014 Didier Roche
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+<refentry id="systemd-machine-id-commit.service">
+
+ <refentryinfo>
+ <title>systemd-machine-id-commit.service</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.service</refentrytitle>
+ <manvolnum>8</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd-machine-id-commit.service</refname>
+ <refpurpose>Commit transient machine-id to disk</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename>systemd-machine-id-commit.service</filename></para>
+ <para><filename>/usr/lib/systemd/systemd-machine-id-commit</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><filename>systemd-machine-id-commit.service</filename> is
+ a service responsible for commiting any transient
+ <filename>/etc/machine-id</filename> file to a writable file
+ system. See
+ <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for more information about this file.</para>
+
+ <para>This service is started shortly after
+ <filename>local-fs.target</filename> if
+ <filename>/etc/machine-id</filename> is an independent mount
+ point (probably a tmpfs one) and /etc is writable.
+ <command>systemd-machine-id-commit</command> 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 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. The main use case for that service is
+ <filename>/etc/machine-id</filename> being an empty file at
+ boot and initrd chaining to systemd giving it a read only file
+ system that will be turned read-write later during the boot
+ process.</para>
+
+ <para>There is no consequence if that service fails other than
+ a newer machine-id will be generated during next system boot.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-machine-id-commit</refentrytitle><manvolnum>1</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>