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<title>16.5.Shutting Down the Server</title>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="postmaster-shutdown"></a>16.5.Shutting Down the Server</h2></div></div></div>
<a name="id644027"></a><p> There are several ways to shut down the database server. You control
the type of shutdown by sending different signals to the
<code class="command">postmaster</code> process.
</p>
<div class="variablelist"><dl>
<dt><span class="term"><span class="systemitem">SIGTERM</span><a name="id644059"></a></span></dt>
<dd><p> After receiving <span class="systemitem">SIGTERM</span>, the server
disallows new connections, but lets existing sessions end their
work normally. It shuts down only after all of the sessions
terminate normally. This is the <em class="firstterm">Smart
Shutdown</em>.
</p></dd>
<dt><span class="term"><span class="systemitem">SIGINT</span><a name="id644090"></a></span></dt>
<dd><p> The server disallows new connections and sends all existing
server processes <span class="systemitem">SIGTERM</span>, which will cause them
to abort their current transactions and exit promptly. It then
waits for the server processes to exit and finally shuts down. This is the
<em class="firstterm">Fast Shutdown</em>.
</p></dd>
<dt><span class="term"><span class="systemitem">SIGQUIT</span><a name="id644123"></a></span></dt>
<dd><p> This is the <em class="firstterm">Immediate Shutdown</em>, which
will cause the <code class="command">postmaster</code> process to send a
<span class="systemitem">SIGQUIT</span> to all child processes and exit
immediately, without properly shutting itself down. The child processes
likewise exit immediately upon receiving
<span class="systemitem">SIGQUIT</span>. This will lead to recovery (by
replaying the WAL log) upon next start-up. This is recommended
only in emergencies.
</p></dd>
</dl></div>
<p>
</p>
<p> The <a href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><a name="app-pg-ctl-title"></a><span class="application">pg_ctl</span></span></a> program provides a convenient
interface for sending these signals to shut down the server.
</p>
<p> Alternatively, you can send the signal directly using <code class="command">kill</code>.
The <acronym class="acronym">PID</acronym> of the <code class="command">postmaster</code> process can be
found using the <code class="command">ps</code> program, or from the file
<code class="filename">postmaster.pid</code> in the data directory. For
example, to do a fast shutdown:
</p>
<pre class="screen">$ <strong class="userinput"><code>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</code></strong></pre>
<p>
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Important</h3>
<p> It is best not to use <span class="systemitem">SIGKILL</span> to shut down
the server. Doing so will prevent the server from releasing
shared memory and semaphores, which may then have to be done
manually before a new server can be started. Furthermore,
<span class="systemitem">SIGKILL</span> kills the <code class="command">postmaster</code>
process without letting it relay the signal to its subprocesses,
so it will be necessary to kill the individual subprocesses by hand as
well.
</p>
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