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><H1
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><A
NAME="SERVER-START"
>17.3. Starting the Database Server</A
></H1
><P
> Before anyone can access the database, you must start the database
server. The database server program is called
<TT
CLASS="COMMAND"
>postgres</TT
>.
The <TT
CLASS="COMMAND"
>postgres</TT
> program must know where to
find the data it is supposed to use. This is done with the
<TT
CLASS="OPTION"
>-D</TT
> option. Thus, the simplest way to start the
server is:
</P><PRE
CLASS="SCREEN"
>$ <KBD
CLASS="USERINPUT"
>postgres -D /usr/local/pgsql/data</KBD
></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 <TT
CLASS="OPTION"
>-D</TT
>, the server will try to use
the data directory named by the environment variable <TT
CLASS="ENVAR"
>PGDATA</TT
>.
If that variable is not provided either, it will fail.
</P
><P
> Normally it is better to start <TT
CLASS="COMMAND"
>postgres</TT
> in the
background. For this, use the usual Unix shell syntax:
</P><PRE
CLASS="SCREEN"
>$ <KBD
CLASS="USERINPUT"
>postgres -D /usr/local/pgsql/data >logfile 2>&1 &</KBD
></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
HREF="logfile-maintenance.html"
>Section 23.3</A
> for a more thorough discussion of log
file handling.)
</P
><P
> The <TT
CLASS="COMMAND"
>postgres</TT
> program also takes a number of other
command-line options. For more information, see the
<A
HREF="app-postgres.html"
><SPAN
CLASS="APPLICATION"
>postgres</SPAN
></A
> reference page
and <A
HREF="runtime-config.html"
>Chapter 18</A
> below.
</P
><P
> This shell syntax can get tedious quickly. Therefore the wrapper
program
<A
HREF="app-pg-ctl.html"
><SPAN
CLASS="APPLICATION"
>pg_ctl</SPAN
></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 <TT
CLASS="OPTION"
>-D</TT
> option has the same meaning
here as for <TT
CLASS="COMMAND"
>postgres</TT
>. <TT
CLASS="COMMAND"
>pg_ctl</TT
>
is also capable of stopping the server.
</P
><P
> Normally, you will want to start the database server when the
computer boots.
Autostart scripts are operating-system-specific.
There are a few distributed with
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> in the
<TT
CLASS="FILENAME"
>contrib/start-scripts</TT
> 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
<TT
CLASS="FILENAME"
>/etc/rc.local</TT
> or
<TT
CLASS="FILENAME"
>/etc/rc.d/rc.local</TT
>. Others use <TT
CLASS="FILENAME"
>init.d</TT
> or
<TT
CLASS="FILENAME"
>rc.d</TT
> directories. Whatever you do, the server must be
run by the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user account
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>and not by root</I
></SPAN
> or any other user. Therefore you
probably should form your commands using
<TT
CLASS="LITERAL"
>su postgres -c '...'</TT
>. 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
></P
></P><UL
><LI
><P
> For <SPAN
CLASS="PRODUCTNAME"
>FreeBSD</SPAN
>, look at the file
<TT
CLASS="FILENAME"
>contrib/start-scripts/freebsd</TT
> in the
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> source distribution.
</P
></LI
><LI
><P
> On <SPAN
CLASS="PRODUCTNAME"
>OpenBSD</SPAN
>, add the following lines
to the file <TT
CLASS="FILENAME"
>/etc/rc.local</TT
>:
</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
><P
> On <SPAN
CLASS="PRODUCTNAME"
>Linux</SPAN
> systems either add
</P><PRE
CLASS="PROGRAMLISTING"
>/usr/local/pgsql/bin/pg_ctl start -l logfile -D /usr/local/pgsql/data</PRE
><P>
to <TT
CLASS="FILENAME"
>/etc/rc.d/rc.local</TT
>
or <TT
CLASS="FILENAME"
>/etc/rc.local</TT
> or look at the file
<TT
CLASS="FILENAME"
>contrib/start-scripts/linux</TT
> in the
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> source distribution.
</P
></LI
><LI
><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.
</P
></LI
><LI
><P
> On <SPAN
CLASS="PRODUCTNAME"
>Solaris</SPAN
>, create a file called
<TT
CLASS="FILENAME"
>/etc/init.d/postgresql</TT
> that contains
the following line:
</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 <TT
CLASS="FILENAME"
>/etc/rc3.d</TT
> as
<TT
CLASS="FILENAME"
>S99postgresql</TT
>.
</P
></LI
></UL
><P>
</P
><P
> While the server is running, its
<ACRONYM
CLASS="ACRONYM"
>PID</ACRONYM
> is stored in the file
<TT
CLASS="FILENAME"
>postmaster.pid</TT
> 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"
><H2
CLASS="SECT2"
><A
NAME="SERVER-START-FAILURES"
>17.3.1. Server Start-up Failures</A
></H2
><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 socket: 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 TCP/IP listen socket</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 <SAMP
CLASS="COMPUTEROUTPUT"
>Address
already in use</SAMP
> 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"
>$ <KBD
CLASS="USERINPUT"
>postgres -p 666</KBD
>
LOG: could not bind IPv4 socket: Permission denied
HINT: Is another postmaster already running on port 666? If not, wait a few seconds and retry.
FATAL: could not create TCP/IP listen socket</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
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"
><I
CLASS="EMPHASIS"
>not</I
></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
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"
>"illegal system call"</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
HREF="kernel-resources.html#SYSVIPC"
>Section 17.4.1</A
>.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="CLIENT-CONNECTION-PROBLEMS"
>17.3.2. Client Connection Problems</A
></H2
><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"
>"I couldn't find a server to talk
to"</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
<SAMP
CLASS="COMPUTEROUTPUT"
>Connection refused</SAMP
> or
<SAMP
CLASS="COMPUTEROUTPUT"
>No such file or directory</SAMP
>, as
illustrated. (It is important to realize that
<SAMP
CLASS="COMPUTEROUTPUT"
>Connection refused</SAMP
> in this context
does <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>not</I
></SPAN
> mean that the server got your
connection request and rejected it. That case will produce a
different message, as shown in <A
HREF="client-authentication-problems.html"
>Section 19.4</A
>.) Other error messages
such as <SAMP
CLASS="COMPUTEROUTPUT"
>Connection timed out</SAMP
> might
indicate more fundamental problems, like lack of network
connectivity.
</P
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