identifiers or numbers must be single-quoted. To embed a single

quote in a parameter value, write either two quotes (preferred)

or backslash-quote.

If the file contains multiple entries for the same parameter,

all but the last one are ignored.

</para>

<para>

In addition to <filename>postgresql.conf</filename>,

a <productname>PostgreSQL</productname> data directory contains a file

<filename>postgresql.auto.conf</filename><indexterm><primary>postgresql.auto.conf</primary></indexterm>,

which has the same format as <filename>postgresql.conf</filename> but should

never be edited manually. This file holds settings provided through

the <xref linkend="sql-altersystem"/> command. This file is automatically

read whenever <filename>postgresql.conf</filename> is, and its settings take

effect in the same way. Settings in <filename>postgresql.auto.conf</filename>

override those in <filename>postgresql.conf</filename>.

which has the same format as <filename>postgresql.conf</filename> but

is intended to be edited automatically not manually. This file holds

settings provided through the <xref linkend="sql-altersystem"/> command.

This file is read whenever <filename>postgresql.conf</filename> is,

and its settings take effect in the same way. Settings

in <filename>postgresql.auto.conf</filename> override those

in <filename>postgresql.conf</filename>.

</para>

<para>

External tools may also

modify <filename>postgresql.auto.conf</filename>. It is not

recommended to do this while the server is running, since a

concurrent <command>ALTER SYSTEM</command> command could overwrite

such changes. Such tools might simply append new settings to the end,

or they might choose to remove duplicate settings and/or comments

(as <command>ALTER SYSTEM</command> will).

</para>

<para>

The system view

<link linkend="view-pg-file-settings"><structname>pg_file_settings</structname></link>

can be helpful for pre-testing changes to the configurationfile, or for

can be helpful for pre-testing changes to the configurationfiles, or for

diagnosing problems if a <systemitem>SIGHUP</systemitem> signal did not have the

desired effects.

</para>