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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>18.3. Starting the Database 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 V1.79.1" /><link rel="prev" href="creating-cluster.html" title="18.2. Creating a Database Cluster" /><link rel="next" href="kernel-resources.html" title="18.4. Managing Kernel Resources" /></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">18.3. Starting the Database Server</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="creating-cluster.html" title="18.2. Creating a Database Cluster">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 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="kernel-resources.html" title="18.4. Managing Kernel Resources">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="SERVER-START"><div class="titlepage"><div><div><h2 class="title" style="clear: both">18.3. Starting the Database Server</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="server-start.html#SERVER-START-FAILURES">18.3.1. Server Start-up Failures</a></span></dt><dt><span class="sect2"><a href="server-start.html#CLIENT-CONNECTION-PROBLEMS">18.3.2. Client Connection Problems</a></span></dt></dl></div><p>
   Before anyone can access the database, you must start the database
   server. The database server program is called
   <code class="command">postgres</code>.<a id="id-1.6.5.5.2.2" class="indexterm"></a>
   The <code class="command">postgres</code> program must know where to
   find the data it is supposed to use. This is done with the
   <code class="option">-D</code> option. Thus, the simplest way to start the
   server is:
</p><pre class="screen">
$ <strong class="userinput"><code>postgres -D /usr/local/pgsql/data</code></strong>
</pre><p>
   which will leave the server running in the foreground. This must be
   done while logged into the <span class="productname">PostgreSQL</span> user
   account. Without <code class="option">-D</code>, the server will try to use
   the data directory named by the environment variable <code class="envar">PGDATA</code>.
   If that variable is not provided either, it will fail.
  </p><p>
   Normally it is better to start <code class="command">postgres</code> in the
   background.  For this, use the usual Unix shell syntax:
</p><pre class="screen">
$ <strong class="userinput"><code>postgres -D /usr/local/pgsql/data &gt;logfile 2&gt;&amp;1 &amp;</code></strong>
</pre><p>
   It is important to store the server's <span class="systemitem">stdout</span> and
   <span class="systemitem">stderr</span> output somewhere, as shown above. It will help
   for auditing purposes and to diagnose problems. (See <a class="xref" href="logfile-maintenance.html" title="24.3. Log File Maintenance">Section 24.3</a> for a more thorough discussion of log
   file handling.)
  </p><p>
   The <code class="command">postgres</code> program also takes a number of other
   command-line options. For more information, see the
   <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a> reference page
   and <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a> below.
  </p><p>
   This shell syntax can get tedious quickly.  Therefore the wrapper
   program
   <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a><a id="id-1.6.5.5.5.2" class="indexterm"></a>
   is provided to simplify some tasks.  For example:
</p><pre class="programlisting">
pg_ctl start -l logfile
</pre><p>
   will start the server in the background and put the output into the
   named log file. The <code class="option">-D</code> option has the same meaning
   here as for <code class="command">postgres</code>. <code class="command">pg_ctl</code>
   is also capable of stopping the server.
  </p><p>
   Normally, you will want to start the database server when the
   computer boots.<a id="id-1.6.5.5.6.1" class="indexterm"></a>
   Autostart scripts are operating-system-specific.
   There are a few distributed with
   <span class="productname">PostgreSQL</span> in the
   <code class="filename">contrib/start-scripts</code> directory. Installing one will require
   root privileges.
  </p><p>
   Different systems have different conventions for starting up daemons
   at boot time. Many systems have a file
   <code class="filename">/etc/rc.local</code> or
   <code class="filename">/etc/rc.d/rc.local</code>. Others use <code class="filename">init.d</code> or
   <code class="filename">rc.d</code> directories. Whatever you do, the server must be
   run by the <span class="productname">PostgreSQL</span> user account
   <span class="emphasis"><em>and not by root</em></span> or any other user. Therefore you
   probably should form your commands using
   <code class="literal">su postgres -c '...'</code>.  For example:
</p><pre class="programlisting">
su postgres -c 'pg_ctl start -D /usr/local/pgsql/data -l serverlog'
</pre><p>
  </p><p>
   Here are a few more operating-system-specific suggestions. (In each
   case be sure to use the proper installation directory and user
   name where we show generic values.)

   </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
      For <span class="productname">FreeBSD</span>, look at the file
      <code class="filename">contrib/start-scripts/freebsd</code> in the
      <span class="productname">PostgreSQL</span> source distribution.
      <a id="id-1.6.5.5.8.1.1.1.4" class="indexterm"></a>
     </p></li><li class="listitem"><p>
      On <span class="productname">OpenBSD</span>, add the following lines
      to the file <code class="filename">/etc/rc.local</code>:
      <a id="id-1.6.5.5.8.1.2.1.3" class="indexterm"></a>
</p><pre class="programlisting">
if [ -x /usr/local/pgsql/bin/pg_ctl -a -x /usr/local/pgsql/bin/postgres ]; then
    su -l postgres -c '/usr/local/pgsql/bin/pg_ctl start -s -l /var/postgresql/log -D /usr/local/pgsql/data'
    echo -n ' postgresql'
fi
</pre><p>
     </p></li><li class="listitem"><p>
      On <span class="productname">Linux</span> systems either add
      <a id="id-1.6.5.5.8.1.3.1.2" class="indexterm"></a>
</p><pre class="programlisting">
/usr/local/pgsql/bin/pg_ctl start -l logfile -D /usr/local/pgsql/data
</pre><p>
      to <code class="filename">/etc/rc.d/rc.local</code>
      or <code class="filename">/etc/rc.local</code> or look at the file
      <code class="filename">contrib/start-scripts/linux</code> in the
      <span class="productname">PostgreSQL</span> source distribution.
     </p><p>
      When using <span class="application">systemd</span>, you can use the following
      service unit file (e.g.,
      at <code class="filename">/etc/systemd/system/postgresql.service</code>):<a id="id-1.6.5.5.8.1.3.2.3" class="indexterm"></a>
</p><pre class="programlisting">
[Unit]
Description=PostgreSQL database server
Documentation=man:postgres(1)

[Service]
Type=notify
User=postgres
ExecStart=/usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data
ExecReload=/bin/kill -HUP $MAINPID
KillMode=mixed
KillSignal=SIGINT
TimeoutSec=0

[Install]
WantedBy=multi-user.target
</pre><p>
      Using <code class="literal">Type=notify</code> requires that the server binary was
      built with <code class="literal">configure --with-systemd</code>.
     </p><p>
      Consider carefully the timeout
      setting.  <span class="application">systemd</span> has a default timeout of 90
      seconds as of this writing and will kill a process that does not notify
      readiness within that time.  But a <span class="productname">PostgreSQL</span>
      server that might have to perform crash recovery at startup could take
      much longer to become ready.  The suggested value of 0 disables the
      timeout logic.
     </p></li><li class="listitem"><p>
      On <span class="productname">NetBSD</span>, use either the
      <span class="productname">FreeBSD</span> or
      <span class="productname">Linux</span> start scripts, depending on
      preference.
      <a id="id-1.6.5.5.8.1.4.1.4" class="indexterm"></a>
     </p></li><li class="listitem"><p>
      On <span class="productname">Solaris</span>, create a file called
      <code class="filename">/etc/init.d/postgresql</code> that contains
      the following line:
      <a id="id-1.6.5.5.8.1.5.1.3" class="indexterm"></a>
</p><pre class="programlisting">
su - postgres -c "/usr/local/pgsql/bin/pg_ctl start -l logfile -D /usr/local/pgsql/data"
</pre><p>
      Then, create a symbolic link to it in <code class="filename">/etc/rc3.d</code> as
      <code class="filename">S99postgresql</code>.
     </p></li></ul></div><p>

  </p><p>
    While the server is running, its
    <acronym class="acronym">PID</acronym> is stored in the file
    <code class="filename">postmaster.pid</code> in the data directory. This is
    used to prevent multiple server instances from
    running in the same data directory and can also be used for
    shutting down the server.
   </p><div class="sect2" id="SERVER-START-FAILURES"><div class="titlepage"><div><div><h3 class="title">18.3.1. Server Start-up Failures</h3></div></div></div><p>
     There are several common reasons the server might fail to
     start. Check the server's log file, or start it by hand (without
     redirecting standard output or standard error) and see what error
     messages appear. Below we explain some of the most common error
     messages in more detail.
    </p><p>
</p><pre class="screen">
LOG:  could not bind IPv4 address "127.0.0.1": Address already in use
HINT:  Is another postmaster already running on port 5432? If not, wait a few seconds and retry.
FATAL:  could not create any TCP/IP sockets
</pre><p>
     This usually means just what it suggests: you tried to start
     another server on the same port where one is already running.
     However, if the kernel error message is not <code class="computeroutput">Address
     already in use</code> or some variant of that, there might
     be a different problem. For example, trying to start a server
     on a reserved port number might draw something like:
</p><pre class="screen">
$ <strong class="userinput"><code>postgres -p 666</code></strong>
LOG:  could not bind IPv4 address "127.0.0.1": Permission denied
HINT:  Is another postmaster already running on port 666? If not, wait a few seconds and retry.
FATAL:  could not create any TCP/IP sockets
</pre><p>
    </p><p>
     A message like:
</p><pre class="screen">
FATAL:  could not create shared memory segment: Invalid argument
DETAIL:  Failed system call was shmget(key=5440001, size=4011376640, 03600).
</pre><p>
     probably means your kernel's limit on the size of shared memory is
     smaller than the work area <span class="productname">PostgreSQL</span>
     is trying to create (4011376640 bytes in this example). Or it could
     mean that you do not have System-V-style shared memory support
     configured into your kernel at all. As a temporary workaround, you
     can try starting the server with a smaller-than-normal number of
     buffers (<a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a>). You will eventually want
     to reconfigure your kernel to increase the allowed shared memory
     size. You might also see this message when trying to start multiple
     servers on the same machine, if their total space requested
     exceeds the kernel limit.
    </p><p>
     An error like:
</p><pre class="screen">
FATAL:  could not create semaphores: No space left on device
DETAIL:  Failed system call was semget(5440126, 17, 03600).
</pre><p>
     does <span class="emphasis"><em>not</em></span> mean you've run out of disk
     space. It means your kernel's limit on the number of <span class="systemitem">System V</span> semaphores is smaller than the number
     <span class="productname">PostgreSQL</span> wants to create. As above,
     you might be able to work around the problem by starting the
     server with a reduced number of allowed connections
     (<a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a>), but you'll eventually want to
     increase the kernel limit.
    </p><p>
     If you get an <span class="quote">“<span class="quote">illegal system call</span>”</span> error, it is likely that
     shared memory or semaphores are not supported in your kernel at
     all. In that case your only option is to reconfigure the kernel to
     enable these features.
    </p><p>
     Details about configuring <span class="systemitem">System V</span>
     <acronym class="acronym">IPC</acronym> facilities are given in <a class="xref" href="kernel-resources.html#SYSVIPC" title="18.4.1. Shared Memory and Semaphores">Section 18.4.1</a>.
    </p></div><div class="sect2" id="CLIENT-CONNECTION-PROBLEMS"><div class="titlepage"><div><div><h3 class="title">18.3.2. Client Connection Problems</h3></div></div></div><p>
     Although the error conditions possible on the client side are quite
     varied and application-dependent, a few of them might be directly
     related to how the server was started. Conditions other than
     those shown below should be documented with the respective client
     application.
    </p><p>
</p><pre class="screen">
psql: could not connect to server: Connection refused
        Is the server running on host "server.joe.com" and accepting
        TCP/IP connections on port 5432?
</pre><p>
     This is the generic <span class="quote">“<span class="quote">I couldn't find a server to talk
     to</span>”</span> failure. It looks like the above when TCP/IP
     communication is attempted. A common mistake is to forget to
     configure the server to allow TCP/IP connections.
    </p><p>
     Alternatively, you'll get this when attempting Unix-domain socket
     communication to a local server:
</p><pre class="screen">
psql: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
</pre><p>
    </p><p>
     The last line is useful in verifying that the client is trying to
     connect to the right place. If there is in fact no server
     running there, the kernel error message will typically be either
     <code class="computeroutput">Connection refused</code> or
     <code class="computeroutput">No such file or directory</code>, as
     illustrated. (It is important to realize that
     <code class="computeroutput">Connection refused</code> in this context
     does <span class="emphasis"><em>not</em></span> mean that the server got your
     connection request and rejected it. That case will produce a
     different message, as shown in <a class="xref" href="client-authentication-problems.html" title="20.15. Authentication Problems">Section 20.15</a>.) Other error messages
     such as <code class="computeroutput">Connection timed out</code> might
     indicate more fundamental problems, like lack of network
     connectivity.
    </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="creating-cluster.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="kernel-resources.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">18.2. Creating a Database Cluster </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 18.4. Managing Kernel Resources</td></tr></table></div></body></html>