systemd/man/systemd-machine-id-commit.service.html
2015-02-17 11:22:16 +01:00

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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="systemd-machine-id-commit.service"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd-machine-id-commit.service — Commit transient machine-id to disk</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename">systemd-machine-id-commit.service</code></p><p><code class="filename">/usr/lib/systemd/systemd-machine-id-commit</code></p></div><div class="refsect1"><a name="idm140406049307488"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description"></a></h2><p><code class="filename">systemd-machine-id-commit.service</code> is a
service responsible for committing any transient
<code class="filename">/etc/machine-id</code> file to a writable file
system. See
<a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>
for more information about this file.</p><p>This service is started shortly after
<code class="filename">local-fs.target</code> if
<code class="filename">/etc/machine-id</code> is an independent mount point
(probably a tmpfs one) and /etc is writable.
<span class="command"><strong>systemd-machine-id-commit</strong></span> will then write
current machine ID to disk and unmount the transient
<code class="filename">/etc/machine-id</code> file in a race-free manner to
ensure that file is always valid for other processes.</p><p>Note that the traditional way to initialize the machine ID
in <code class="filename">/etc/machine-id</code> is to use
<span class="command"><strong>systemd-machine-id-setup</strong></span> by system installer
tools. You can also use
<a href="systemd-firstboot.html"><span class="citerefentry"><span class="refentrytitle">systemd-firstboot</span>(1)</span></a>
to initialize the machine ID on mounted (but not booted) system
images. The main use case for that service is
<code class="filename">/etc/machine-id</code> 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.</p><p>There is no consequence if that service fails other than a
newer machine-id will be generated during next system boot.
</p></div><div class="refsect1"><a name="idm140406049296752"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also"></a></h2><p>
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
<a href="systemd-machine-id-commit.html"><span class="citerefentry"><span class="refentrytitle">systemd-machine-id-commit</span>(1)</span></a>,
<a href="systemd-machine-id-setup.html"><span class="citerefentry"><span class="refentrytitle">systemd-machine-id-setup</span>(1)</span></a>,
<a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>,
<a href="systemd-firstboot.html"><span class="citerefentry"><span class="refentrytitle">systemd-firstboot</span>(1)</span></a>
</p></div></div></body></html>