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2 <!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 Vsnapshot" /><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 id="docContent" class="container-fluid col-10"><div 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 18.0 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 /></div><div class="sect1" id="SERVER-START"><div class="titlepage"><div><div><h2 class="title" style="clear: both">18.3. Starting the Database Server <a href="#SERVER-START" class="id_link">#</a></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>
3 Before anyone can access the database, you must start the database
4 server. The database server program is called
5 <code class="command">postgres</code>.<a id="id-1.6.5.6.2.2" class="indexterm"></a>
7 If you are using a pre-packaged version
8 of <span class="productname">PostgreSQL</span>, it almost certainly includes
9 provisions for running the server as a background task according to the
10 conventions of your operating system. Using the package's
11 infrastructure to start the server will be much less work than figuring
12 out how to do this yourself. Consult the package-level documentation
15 The bare-bones way to start the server manually is just to invoke
16 <code class="command">postgres</code> directly, specifying the location of the
17 data directory with the <code class="option">-D</code> option, for example:
18 </p><pre class="screen">
19 $ <strong class="userinput"><code>postgres -D /usr/local/pgsql/data</code></strong>
21 which will leave the server running in the foreground. This must be
22 done while logged into the <span class="productname">PostgreSQL</span> user
23 account. Without <code class="option">-D</code>, the server will try to use
24 the data directory named by the environment variable <code class="envar">PGDATA</code>.
25 If that variable is not provided either, it will fail.
27 Normally it is better to start <code class="command">postgres</code> in the
28 background. For this, use the usual Unix shell syntax:
29 </p><pre class="screen">
30 $ <strong class="userinput"><code>postgres -D /usr/local/pgsql/data >logfile 2>&1 &</code></strong>
32 It is important to store the server's <span class="systemitem">stdout</span> and
33 <span class="systemitem">stderr</span> output somewhere, as shown above. It will help
34 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
37 The <code class="command">postgres</code> program also takes a number of other
38 command-line options. For more information, see the
39 <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a> reference page
40 and <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a> below.
42 This shell syntax can get tedious quickly. Therefore the wrapper
44 <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-1.6.5.6.7.2" class="indexterm"></a>
45 is provided to simplify some tasks. For example:
46 </p><pre class="programlisting">
47 pg_ctl start -l logfile
49 will start the server in the background and put the output into the
50 named log file. The <code class="option">-D</code> option has the same meaning
51 here as for <code class="command">postgres</code>. <code class="command">pg_ctl</code>
52 is also capable of stopping the server.
54 Normally, you will want to start the database server when the
55 computer boots.<a id="id-1.6.5.6.8.1" class="indexterm"></a>
56 Autostart scripts are operating-system-specific.
57 There are a few example scripts distributed with
58 <span class="productname">PostgreSQL</span> in the
59 <code class="filename">contrib/start-scripts</code> directory. Installing one will require
62 Different systems have different conventions for starting up daemons
63 at boot time. Many systems have a file
64 <code class="filename">/etc/rc.local</code> or
65 <code class="filename">/etc/rc.d/rc.local</code>. Others use <code class="filename">init.d</code> or
66 <code class="filename">rc.d</code> directories. Whatever you do, the server must be
67 run by the <span class="productname">PostgreSQL</span> user account
68 <span class="emphasis"><em>and not by root</em></span> or any other user. Therefore you
69 probably should form your commands using
70 <code class="literal">su postgres -c '...'</code>. For example:
71 </p><pre class="programlisting">
72 su postgres -c 'pg_ctl start -D /usr/local/pgsql/data -l serverlog'
75 Here are a few more operating-system-specific suggestions. (In each
76 case be sure to use the proper installation directory and user
77 name where we show generic values.)
79 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
80 For <span class="productname">FreeBSD</span>, look at the file
81 <code class="filename">contrib/start-scripts/freebsd</code> in the
82 <span class="productname">PostgreSQL</span> source distribution.
83 <a id="id-1.6.5.6.10.1.1.1.4" class="indexterm"></a>
84 </p></li><li class="listitem"><p>
85 On <span class="productname">OpenBSD</span>, add the following lines
86 to the file <code class="filename">/etc/rc.local</code>:
87 <a id="id-1.6.5.6.10.1.2.1.3" class="indexterm"></a>
88 </p><pre class="programlisting">
89 if [ -x /usr/local/pgsql/bin/pg_ctl -a -x /usr/local/pgsql/bin/postgres ]; then
90 su -l postgres -c '/usr/local/pgsql/bin/pg_ctl start -s -l /var/postgresql/log -D /usr/local/pgsql/data'
94 </p></li><li class="listitem"><p>
95 On <span class="productname">Linux</span> systems either add
96 <a id="id-1.6.5.6.10.1.3.1.2" class="indexterm"></a>
97 </p><pre class="programlisting">
98 /usr/local/pgsql/bin/pg_ctl start -l logfile -D /usr/local/pgsql/data
100 to <code class="filename">/etc/rc.d/rc.local</code>
101 or <code class="filename">/etc/rc.local</code> or look at the file
102 <code class="filename">contrib/start-scripts/linux</code> in the
103 <span class="productname">PostgreSQL</span> source distribution.
105 When using <span class="application">systemd</span>, you can use the following
106 service unit file (e.g.,
107 at <code class="filename">/etc/systemd/system/postgresql.service</code>):<a id="id-1.6.5.6.10.1.3.2.3" class="indexterm"></a>
108 </p><pre class="programlisting">
110 Description=PostgreSQL database server
111 Documentation=man:postgres(1)
112 After=network-online.target
113 Wants=network-online.target
118 ExecStart=/usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data
119 ExecReload=/bin/kill -HUP $MAINPID
125 WantedBy=multi-user.target
127 Using <code class="literal">Type=notify</code> requires that the server binary was
128 built with <code class="literal">configure --with-systemd</code>.
130 Consider carefully the timeout
131 setting. <span class="application">systemd</span> has a default timeout of 90
132 seconds as of this writing and will kill a process that does not report
133 readiness within that time. But a <span class="productname">PostgreSQL</span>
134 server that might have to perform crash recovery at startup could take
135 much longer to become ready. The suggested value
136 of <code class="literal">infinity</code> disables the timeout logic.
137 </p></li><li class="listitem"><p>
138 On <span class="productname">NetBSD</span>, use either the
139 <span class="productname">FreeBSD</span> or
140 <span class="productname">Linux</span> start scripts, depending on
142 <a id="id-1.6.5.6.10.1.4.1.4" class="indexterm"></a>
143 </p></li><li class="listitem"><p>
144 On <span class="productname">Solaris</span>, create a file called
145 <code class="filename">/etc/init.d/postgresql</code> that contains
147 <a id="id-1.6.5.6.10.1.5.1.3" class="indexterm"></a>
148 </p><pre class="programlisting">
149 su - postgres -c "/usr/local/pgsql/bin/pg_ctl start -l logfile -D /usr/local/pgsql/data"
151 Then, create a symbolic link to it in <code class="filename">/etc/rc3.d</code> as
152 <code class="filename">S99postgresql</code>.
153 </p></li></ul></div><p>
156 While the server is running, its
157 <acronym class="acronym">PID</acronym> is stored in the file
158 <code class="filename">postmaster.pid</code> in the data directory. This is
159 used to prevent multiple server instances from
160 running in the same data directory and can also be used for
161 shutting down the server.
162 </p><div class="sect2" id="SERVER-START-FAILURES"><div class="titlepage"><div><div><h3 class="title">18.3.1. Server Start-up Failures <a href="#SERVER-START-FAILURES" class="id_link">#</a></h3></div></div></div><p>
163 There are several common reasons the server might fail to
164 start. Check the server's log file, or start it by hand (without
165 redirecting standard output or standard error) and see what error
166 messages appear. Below we explain some of the most common error
167 messages in more detail.
169 </p><pre class="screen">
170 LOG: could not bind IPv4 address "127.0.0.1": Address already in use
171 HINT: Is another postmaster already running on port 5432? If not, wait a few seconds and retry.
172 FATAL: could not create any TCP/IP sockets
174 This usually means just what it suggests: you tried to start
175 another server on the same port where one is already running.
176 However, if the kernel error message is not <code class="computeroutput">Address
177 already in use</code> or some variant of that, there might
178 be a different problem. For example, trying to start a server
179 on a reserved port number might draw something like:
180 </p><pre class="screen">
181 $ <strong class="userinput"><code>postgres -p 666</code></strong>
182 LOG: could not bind IPv4 address "127.0.0.1": Permission denied
183 HINT: Is another postmaster already running on port 666? If not, wait a few seconds and retry.
184 FATAL: could not create any TCP/IP sockets
188 </p><pre class="screen">
189 FATAL: could not create shared memory segment: Invalid argument
190 DETAIL: Failed system call was shmget(key=5440001, size=4011376640, 03600).
192 probably means your kernel's limit on the size of shared memory is
193 smaller than the work area <span class="productname">PostgreSQL</span>
194 is trying to create (4011376640 bytes in this example).
195 This is only likely to happen if you have set <code class="literal">shared_memory_type</code>
196 to <code class="literal">sysv</code>. In that case, you
197 can try starting the server with a smaller-than-normal number of
198 buffers (<a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a>), or
199 reconfigure your kernel to increase the allowed shared memory
200 size. You might also see this message when trying to start multiple
201 servers on the same machine, if their total space requested
202 exceeds the kernel limit.
205 </p><pre class="screen">
206 FATAL: could not create semaphores: No space left on device
207 DETAIL: Failed system call was semget(5440126, 17, 03600).
209 does <span class="emphasis"><em>not</em></span> mean you've run out of disk
210 space. It means your kernel's limit on the number of <span class="systemitem">System V</span> semaphores is smaller than the number
211 <span class="productname">PostgreSQL</span> wants to create. As above,
212 you might be able to work around the problem by starting the
213 server with a reduced number of allowed connections
214 (<a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a>), but you'll eventually want to
215 increase the kernel limit.
217 Details about configuring <span class="systemitem">System V</span>
218 <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>.
219 </p></div><div class="sect2" id="CLIENT-CONNECTION-PROBLEMS"><div class="titlepage"><div><div><h3 class="title">18.3.2. Client Connection Problems <a href="#CLIENT-CONNECTION-PROBLEMS" class="id_link">#</a></h3></div></div></div><p>
220 Although the error conditions possible on the client side are quite
221 varied and application-dependent, a few of them might be directly
222 related to how the server was started. Conditions other than
223 those shown below should be documented with the respective client
226 </p><pre class="screen">
227 psql: error: connection to server at "server.joe.com" (123.123.123.123), port 5432 failed: Connection refused
228 Is the server running on that host and accepting TCP/IP connections?
230 This is the generic <span class="quote">“<span class="quote">I couldn't find a server to talk
231 to</span>”</span> failure. It looks like the above when TCP/IP
232 communication is attempted. A common mistake is to forget to
233 configure <a class="xref" href="runtime-config-connection.html#GUC-LISTEN-ADDRESSES">listen_addresses</a> so that the server
234 accepts remote TCP connections.
236 Alternatively, you might get this when attempting Unix-domain socket
237 communication to a local server:
238 </p><pre class="screen">
239 psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such file or directory
240 Is the server running locally and accepting connections on that socket?
242 If the server is indeed running, check that the client's idea of the
243 socket path (here <code class="literal">/tmp</code>) agrees with the server's
244 <a class="xref" href="runtime-config-connection.html#GUC-UNIX-SOCKET-DIRECTORIES">unix_socket_directories</a> setting.
246 A connection failure message always shows the server address or socket
247 path name, which is useful in verifying that the client is trying to
248 connect to the right place. If there is in fact no server
249 listening there, the kernel error message will typically be either
250 <code class="computeroutput">Connection refused</code> or
251 <code class="computeroutput">No such file or directory</code>, as
252 illustrated. (It is important to realize that
253 <code class="computeroutput">Connection refused</code> in this context
254 does <span class="emphasis"><em>not</em></span> mean that the server got your
255 connection request and rejected it. That case will produce a
256 different message, as shown in <a class="xref" href="client-authentication-problems.html" title="20.16. Authentication Problems">Section 20.16</a>.) Other error messages
257 such as <code class="computeroutput">Connection timed out</code> might
258 indicate more fundamental problems, like lack of network
259 connectivity, or a firewall blocking the connection.
260 </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" title="18.2. Creating a Database Cluster">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime.html" title="Chapter 18. Server Setup and Operation">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="kernel-resources.html" title="18.4. Managing Kernel Resources">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" title="PostgreSQL 18.0 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 18.4. Managing Kernel Resources</td></tr></table></div></body></html>
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