man/systemd-shutdown.html

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  22   <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 218</span><hr><div class="refentry"><a name="systemd-halt.service"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd-halt.service, systemd-poweroff.service, systemd-reboot.service, systemd-kexec.service, systemd-shutdown — System shutdown logic</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename">systemd-halt.service</code></p><p><code class="filename">systemd-poweroff.service</code></p><p><code class="filename">systemd-reboot.service</code></p><p><code class="filename">systemd-kexec.service</code></p><p><code class="filename">/usr/lib/systemd/systemd-shutdown</code></p></div><div class="refsect1"><a name="idm139801696152736"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="filename">systemd-halt.service</code> is a
  23                 system service that is pulled in by
  24                 <code class="filename">halt.target</code> and is responsible
  25                 for the actual system halt. Similarly,
  26                 <code class="filename">systemd-poweroff.service</code> is
  27                 pulled in by <code class="filename">poweroff.target</code>,
  28                 <code class="filename">systemd-reboot.service</code> by
  29                 <code class="filename">reboot.target</code> and
  30                 <code class="filename">systemd-kexec.service</code> by
  31                 <code class="filename">kexec.target</code> to execute the
  32                 respective actions.</p><p>When these services are run, they ensure that PID
  33                 1 is replaced by the
  34                 <code class="filename">/usr/lib/systemd/systemd-shutdown</code>
  35                 tool which is then responsible for the actual
  36                 shutdown. Before shutting down, this binary will try to
  37                 unmount all remaining file systems, disable all
  38                 remaining swap devices, detach all remaining storage
  39                 devices and kill all remaining processes.</p><p>It is necessary to have this code in a separate binary
  40                 because otherwise rebooting after an upgrade might be broken —
  41                 the running PID 1 could still depend on libraries which are not
  42                 available any more, thus keeping the file system busy, which
  43                 then cannot be re-mounted read-only.</p><p>Immediately before executing the actual system
  44                 halt/poweroff/reboot/kexec
  45                 <code class="filename">systemd-shutdown</code> will run all
  46                 executables in
  47                 <code class="filename">/usr/lib/systemd/system-shutdown/</code>
  48                 and pass one arguments to them: either
  49                 "<code class="literal">halt</code>",
  50                 "<code class="literal">poweroff</code>",
  51                 "<code class="literal">reboot</code>" or
  52                 "<code class="literal">kexec</code>", depending on the chosen
  53                 action. All executables in this directory are executed
  54                 in parallel, and execution of the action is not
  55                 continued before all executables finished.</p><p>Note that
  56                 <code class="filename">systemd-halt.service</code> (and the
  57                 related units) should never be executed
  58                 directly. Instead, trigger system shutdown with a
  59                 command such as "<code class="literal">systemctl halt</code>" or
  60                 suchlike.</p></div><div class="refsect1"><a name="idm139801700089120"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
  61                         <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
  62                         <a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>,
  63                         <a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a>,
  64                         <a href="http://man7.org/linux/man-pages/man2/reboot.2.html"><span class="citerefentry"><span class="refentrytitle">reboot</span>(2)</span></a>,
  65                         <a href="systemd-suspend.service.html"><span class="citerefentry"><span class="refentrytitle">systemd-suspend.service</span>(8)</span></a>
  66                 </p></div></div></body></html>