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<chapter id="maintenance">

</para>

<para>

If you simply direct the <systemitem>stderr</> of the <command>postmaster</command> into a

file, the only way to truncate the log file is to stop and restart

If you simply direct the <systemitem>stderr</> of the

<command>postmaster</command> into a

file, you will have log output, but

the only way to truncate the log file is to stop and restart

the <command>postmaster</command>. This may be OK if you are using

<productname>PostgreSQL</productname> in a development environment,

but few production servers would find this behavior acceptable.

</para>

<para>

The simplest production-grade approach to managing log output is to

A better approach is to send the <command>postmaster</>'s

<systemitem>stderr</> output to some type of log rotation program.

There is a built-in log rotation program, which you can use by

setting the configuration parameter <literal>redirect_stderr</> to

<literal>true</> in <filename>postgresql.conf</>. The control

parameters for this program are described in <xref

linkend="runtime-config-logging-where">.

</para>

<para>

Alternatively, you might prefer to use an external log rotation

program, if you have one that you are already using with other

server software. For example, the <application>rotatelogs</application>

tool included in the <productname>Apache</productname> distribution

can be used with <productname>PostgreSQL</productname>. To do this,

just pipe the <command>postmaster</>'s

<systemitem>stderr</> output to the desired program.

If you start the server with

<command>pg_ctl</>, then <systemitem>stderr</>

is already redirected to <systemitem>stdout</>, so you just need a

pipe command:

<programlisting>

pg_ctl start | rotatelogs /var/log/pgsql_log 86400

</programlisting>

</para>

<para>

Another production-grade approach to managing log output is to

send it all to <application>syslog</> and let

<application>syslog</> deal with file rotation. To do this, set the

configuration parameter <literal>log_destination</> to'syslog' (to log to

<application>syslog</> only) in <filename>postgresql.conf</>. Then

you can send a <literal>SIGHUP</literal> signal to the

<application>syslog</> daemon whenever you want to force it to

start writing a new log file. If you want to automate log

configuration parameter <literal>log_destination</> to<literal>syslog</>

(to log to<application>syslog</> only) in

<filename>postgresql.conf</>. Thenyou can send a <literal>SIGHUP</literal>

signal to the<application>syslog</> daemon whenever you want to force it

tostart writing a new log file. If you want to automate log

rotation, the <application>logrotate</application> program can be

configured to work with log files from

<application>syslog</application>.

particularly with large log messages; it may truncate or drop messages

just when you need them the most. Also, on <productname>linux</>,

<application>syslog</> will sync each message to disk, yielding poor

performance.Use a <literal>-</> at the start of the file name

in the <application>syslog</> config file to disable this behavior.

performance.(You can use a <literal>-</> at the start of the file name

in the <application>syslog</> config file to disable this behavior.)

</para>

<para>

You may find it more useful to pipe the

<systemitem>stderr</> of the <command>postmaster</> to some type of

log rotation program. If you start the server with

<command>pg_ctl</>, then the <systemitem>stderr</> of the <command>postmaster</command>

is already redirected to <systemitem>stdout</>, so you just need a

pipe command:

<programlisting>

pg_ctl start | rotatelogs /var/log/pgsql_log 86400

</programlisting>

The <productname>PostgreSQL</> distribution doesn't include a

suitable log rotation program, but there are many available on the

Internet. For example, the <application>rotatelogs</application>

tool included in the <productname>Apache</productname> distribution

can be used with <productname>PostgreSQL</productname>.

Note that all the solutions described above take care of starting new

log files at configurable intervals, but they do not handle deletion

of old, no-longer-interesting log files. You will also want to set

up a batch job to periodically delete old log files.

</para>

</sect1>

</chapter>

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<Chapter Id="runtime">

option to a list of desired log destinations separated by

commas. The default is to log to <systemitem>stderr</systemitem>

only.

This option can only be set at server start or in the

<filename>postgresql.conf</filename> configuration file.

</para>

</listitem>

</varlistentry>

<varlistentry id="guc-redirect-stderr" xreflabel="redirect_stderr">

<term><varname>redirect_stderr</varname> (<type>boolean</type>)</term>

<listitem>

<para>

This option allows messages sent to <application>stderr</> to be

captured and redirected into log files.

This option, in combination with logging to <application>stderr</>,

is often more useful than

logging to <application>syslog</>, since some types of messages

may not appear in <application>syslog</> output (a common example

is dynamic-linker failure messages).

This option can only be set at server start.

</para>

</listitem>

</varlistentry>

<varlistentry id="guc-log-directory" xreflabel="log_directory">

<term><varname>log_directory</varname> (<type>string</type>)</term>

<listitem>

<para>

When <varname>redirect_stderr</> is enabled, this option

determines the directory in which log files will be created.

It may be specified as an absolute path, or relative to the

cluster data directory.

This option can only be set at server start or in the

<filename>postgresql.conf</filename> configuration file.

</para>

</listitem>

</varlistentry>

<varlistentry id="guc-log-filename-prefix" xreflabel="log_filename_prefix">

<term><varname>log_filename_prefix</varname> (<type>string</type>)</term>

<listitem>

<para>

When <varname>redirect_stderr</> is enabled, this option

sets the prefix of the file names of the created log files.

The postmaster PID and the current time are appended to this

prefix to form an exact log file name.

This option can only be set at server start or in the

<filename>postgresql.conf</filename> configuration file.

</para>

</listitem>

</varlistentry>

<varlistentry id="guc-log-rotation-age" xreflabel="log_rotation_age">

<term><varname>log_rotation_age</varname> (<type>integer</type>)</term>

<listitem>

<para>

When <varname>redirect_stderr</> is enabled, this option

determines the maximum lifetime of an individual log file.

After this many minutes have elapsed, a new log file will

be created. Set to zero to disable time-based creation of

new log files.

This option can only be set at server start or in the

<filename>postgresql.conf</filename> configuration file.

</para>

</listitem>

</varlistentry>

<varlistentry id="guc-log-rotation-size" xreflabel="log_rotation_size">

<term><varname>log_rotation_size</varname> (<type>integer</type>)</term>

<listitem>

<para>

When <varname>redirect_stderr</> is enabled, this option

determines the maximum size of an individual log file.

After this many kilobytes have been emitted into a log file,

a new log file will be created. Set to zero to disable size-based

creation of new log files.

This option can only be set at server start or in the

<filename>postgresql.conf</filename> configuration file.

</para>

</listitem>

</varlistentry>

<varlistentry id="guc-syslog-facility" xreflabel="syslog_facility">

<term><varname>syslog_facility</varname> (<type>string</type>)</term>

<listitem>

<para>

If logging to <application>syslog</> is enabled, this option

When logging to <application>syslog</> is enabled, this option

determines the <application>syslog</application>

<quote>facility</quote> to be used. You may choose

from <literal>LOCAL0</>, <literal>LOCAL1</>,

<term><varname>syslog_ident</varname> (<type>string</type>)</term>

<listitem>

<para>

If logging to <application>syslog</> is enabled, this option

When logging to <application>syslog</> is enabled, this option

determines the program name used to identify

<productname>PostgreSQL</productname> messages in

<application>syslog</application> logs. The default is

subdir = src/backend/postmaster

top_builddir = ../../..

include$(top_builddir)/src/Makefile.global

OBJS = postmaster.o bgwriter.o pgstat.o pgarch.o

OBJS = postmaster.o bgwriter.o pgstat.o pgarch.o syslogger.o

all: SUBSYS.o

beos_backend_startup();

ClosePostmasterPorts();

ClosePostmasterPorts(false);

PGSharedMemoryDetach();

beos_backend_startup();

ClosePostmasterPorts();

ClosePostmasterPorts(false);

PGSharedMemoryDetach();