systemd/man/systemd-machine-id-commit.service.xml
Lennart Poettering 4a9b1dd4ad machine-id-commit: merge machine-id-commit functionality into machine-id-setup
And remove machine-id-commit as separate binary.

There's really no point in keeping this separate, as the sources are
pretty much identical, and have pretty identical interfaces. Let's unify
this in one binary.

Given that machine-id-commit was a private binary of systemd (shipped in
/usr/lib/) removing the tool is not an API break.

While we are at it, improve the documentation of the command substantially.
2015-09-29 21:55:51 +02:00

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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">
<!--
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Copyright 2014 Didier Roche
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<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 a transient machine-id to disk</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-machine-id-commit.service</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<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 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 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-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>