<?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" [
-<!ENTITY % entities SYSTEM "custom-entities.ent" >
-%entities;
-]>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
- This file is part of systemd.
+ SPDX-License-Identifier: LGPL-2.1+
- 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.
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- systemd is distributed in the hope that it will be useful, but
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- Lesser General Public License for more details.
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- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
+ Copyright © 2014 Didier Roche
-->
<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>
<refnamediv>
<refname>systemd-machine-id-commit.service</refname>
- <refpurpose>Commit transient machine-id to disk</refpurpose>
+ <refpurpose>Commit a transient machine ID to disk</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-machine-id-commit.service</filename></para>
- <para><filename>&rootlibexecdir;/systemd-machine-id-commit</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para><filename>systemd-machine-id-commit.service</filename> is a
- service responsible for committing any transient
- <filename>/etc/machine-id</filename> file to a writable file
+ <para><filename>systemd-machine-id-commit.service</filename> is an
+ early boot service responsible for committing transient
+ <filename>/etc/machine-id</filename> files to a writable disk 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
+ for more information about machine IDs.</para>
+
+ <para>This service is started after
+ <filename>local-fs.target</filename> in case
+ <filename>/etc/machine-id</filename> is a mount point of its own
+ (usually from a memory file system such as
+ <literal>tmpfs</literal>) and /etc is writable. The service will
+ invoke <command>systemd-machine-id-setup --commit</command>, which
+ writes the current transient machine ID to disk and unmount the
<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>
+ ensure that file is always valid and accessible for other
+ processes. See
+ <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ for details.</para>
+
+ <para>The main use case of this service are systems where
+ <filename>/etc/machine-id</filename> is read-only and initially
+ not initialized. In this case, the system manager will generate a
+ transient machine ID file on a memory file system, and mount it
+ over <filename>/etc/machine-id</filename>, during the early boot
+ phase. This service is then invoked in a later boot phase, as soon
+ as <filename>/etc</filename> has been remounted writable and the
+ ID may thus be committed to disk to make it permanent.</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>
projects / thirdparty / systemd.git / blobdiff