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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>18.5. Shutting Down the Server</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="kernel-resources.html" title="18.4. Managing Kernel Resources" /><link rel="next" href="upgrading.html" title="18.6. Upgrading a PostgreSQL Cluster" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">18.5. Shutting Down the Server</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="kernel-resources.html" title="18.4. Managing Kernel Resources">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="runtime.html" title="Chapter 18. Server Setup and Operation">Up</a></td><th width="60%" align="center">Chapter 18. Server Setup and Operation</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="upgrading.html" title="18.6. Upgrading a PostgreSQL Cluster">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="SERVER-SHUTDOWN"><div class="titlepage"><div><div><h2 class="title" style="clear: both">18.5. Shutting Down the Server</h2></div></div></div><a id="id-1.6.5.7.2" class="indexterm"></a><p>
There are several ways to shut down the database server. You control
the type of shutdown by sending different signals to the master
<code class="command">postgres</code> process.
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="systemitem">SIGTERM</span><a id="id-1.6.5.7.3.2.1.1.2" class="indexterm"></a></span></dt><dd><p>
This is the <em class="firstterm">Smart Shutdown</em> mode.
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.
If the server is in online backup mode, it additionally waits
until online backup mode is no longer active. While backup mode is
active, new connections will still be allowed, but only to superusers
(this exception allows a superuser to connect to terminate
online backup mode). If the server is in recovery when a smart
shutdown is requested, recovery and streaming replication will be
stopped only after all regular sessions have terminated.
</p></dd><dt><span class="term"><span class="systemitem">SIGINT</span><a id="id-1.6.5.7.3.2.2.1.2" class="indexterm"></a></span></dt><dd><p>
This is the <em class="firstterm">Fast Shutdown</em> mode.
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 all server processes to exit and finally shuts down.
If the server is in online backup mode, backup mode will be
terminated, rendering the backup useless.
</p></dd><dt><span class="term"><span class="systemitem">SIGQUIT</span><a id="id-1.6.5.7.3.2.3.1.2" class="indexterm"></a></span></dt><dd><p>
This is the <em class="firstterm">Immediate Shutdown</em> mode.
The server will send <span class="systemitem">SIGQUIT</span> to all child
processes and wait for them to terminate. If any do not terminate
within 5 seconds, they will be sent <span class="systemitem">SIGKILL</span>.
The master server process exits as soon as all child processes have
exited, without doing normal database shutdown processing.
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 class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a> program provides a convenient
interface for sending these signals to shut down the server.
Alternatively, you can send the signal directly using <code class="command">kill</code>
on non-Windows systems.
The <acronym class="acronym">PID</acronym> of the <code class="command">postgres</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"><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 might then have to be done
manually before a new server can be started. Furthermore,
<span class="systemitem">SIGKILL</span> kills the <code class="command">postgres</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></div><p>
To terminate an individual session while allowing other sessions to
continue, use <code class="function">pg_terminate_backend()</code> (see <a class="xref" href="functions-admin.html#FUNCTIONS-ADMIN-SIGNAL-TABLE" title="Table 9.78. Server Signaling Functions">Table 9.78</a>) or send a
<span class="systemitem">SIGTERM</span> signal to the child process associated with
the session.
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