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<listitem>

<para>

Default datadirection location

Default datadirectory location

</para>

</listitem>

</varlistentry>

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One <command>postmaster</command> always manages the data

from exactly one database cluster. A database cluster is a

collection of databases that is stored at a common file system

location. When the <command>postmaster</command> starts it needs

to know the location of the database cluster files (<quote>data

area</quote>).

location (the <quote>data area</quote>).

More than one <command>postmaster</command> process can run on a system

at one time as long as they use different data areas and different

at one time, so long as they use different data areas and different

communication ports (see below). A data area is created with <xref

linkend="app-initdb">.

</para>

<para>

The <quote>data area</> is specified by the <option>-D</option> option

When the <command>postmaster</command> starts it needs

to know the location of the data area.

The location must be specified by the <option>-D</option> option

or the <envar>PGDATA</envar> environment variable; there is no default.

Typically, it points to a directory created by <application>

initdb</>. However, for administrative flexibility, you can

point to a directory containing only configuration files:

<filename>postgresql.conf</>, <filename>pg_hba.conf</>, and

<filename>pg_ident.conf</>. You can then set

<filename>postgresql.conf</>'s <varname>pgdata</> variable to point to the

data directory. You can also point just to the server configuration file

like <filename>postgresql.conf</> and set its variables to point to the

other configuration files and the data directory.

Typically, <option>-D</option> or <envar>PGDATA</envar> points

directly to the data area directory created by <application>initdb</>.

Other possible file layouts are discussed in

<xref linkend="runtime-config-file-locations">.

</para>

</refsect1>

<term><option>-D <replaceable class="parameter">datadir</replaceable></option></term>

<listitem>

<para>

Specifies the file system location of the data directory. See

discussion above.

Specifies the file system location of the data directory or

configuration file(s). See

<xref linkend="runtime-config-file-locations"> for details.

</para>

</listitem>

</varlistentry>

<listitem>

<para>

Default datadirection location

Default datadirectory location

</para>

</listitem>

</varlistentry>

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<Chapter Id="runtime">

any desired selection condition.

</para>

<sect2 id="runtime-config-configuration-files">

<title>Configuration Files</title>

<sect2 id="runtime-config-file-locations">

<title>File Locations</title>

<variablelist>

<varlistentry id="guc-pgdata" xreflabel="pgdata">

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

<listitem>

<para>

Specifies the directory to use for data storage (everything except

configuration files).

Specifies the directory to use for data storage.

This option can only be set at server start.

</para>

</listitem>

</varlistentry>

<para>

Specifies the file name to use for configuration of host-based

authentication (HBA).

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

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

</para>

</listitem>

</varlistentry>

<para>

Specifies the file name to use for configuration of

<application>ident</> authentication.

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

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

</para>

</listitem>

</varlistentry>

<para>

Specifies the location of an additional <application>postmaster</>

process-id (PID) file for use by server administration programs.

This option can only be set at server start.

</para>

</listitem>

</varlistentry>

</variablelist>

<para>

In a default installation, none of the above options is set explicitly

in the <filename>postgresql.conf</filename> file. In this case, the

data directory is specified by the <option>-D</option> command-line

option or the <envar>PGDATA</envar> environment variable; there is no

default for it. The configuration files are all placed within the

data directory.

</para>

<para>

It is also possible to separate the configuration files from the data

directory, which can ease administration. (In particular it is often

easier to ensure that the configuration files are properly backed-up

when they are kept separate.) To do this, the <option>-D</option>

command-line option or <envar>PGDATA</envar> environment variable

must point to the directory containing the configuration files,

and the <varname>pgdata</> option is set in

<filename>postgresql.conf</filename> (or on the command line) to show

where the data directory is actually located.

</para>

<para>

If you wish, you can also make the <option>-D</option>

command-line option or <envar>PGDATA</envar> environment variable

point directly to the master configuration file (which then need not be

named <filename>postgresql.conf</filename>). The <varname>pgdata</>

option must be set to determine the data directory location.

The other configuration files will by default be sought

in the data directory.

</para>

<para>

With any of these approaches, you can specify the locations of the

secondary configuration files (<filename>pg_hba.conf</> and

<filename>pg_ident.conf</>) by setting <varname>hba_conf</> and/or

<varname>ident_conf</> in the master configuration file. These options

override the normal locations and names of the secondary files.

</para>

</sect2>

<sect2 id="runtime-config-connection">

char*dbname;

intflag;

intxlogop=BS_XLOG_NOP;

char*userPGDATA=NULL;

char*userDoption=NULL;

dbname=NULL;

if (!IsUnderPostmaster)

{

InitializeGUCOptions();

userPGDATA=getenv("PGDATA");/* Null if no PGDATA variable */

}

if (argc>1&&strcmp(argv[1],"-boot")==0)

switch (flag)

{

case'D':

userPGDATA=optarg;

userDoption=optarg;

break;

case'd':

{

if (!dbname||argc!=optind)

usage();

if (!IsUnderPostmaster)

{

if (!userPGDATA)

{

write_stderr("%s does not know where to find the database system data.\n"

"PGDATA environment variable.\n",

argv[0]);

proc_exit(1);

}

SetDataDir(userPGDATA);

}

Assert(DataDir);

ValidatePgVersion(DataDir);

if (!IsUnderPostmaster)

{

ProcessConfigFile(PGC_POSTMASTER);

pg_timezone_initialize();

if (!SelectConfigFiles(userDoption,argv[0]))

proc_exit(1);

}

Assert(DataDir);

ValidatePgVersion(DataDir);

if (!IsUnderPostmaster)

CreateDataDirLockFile(DataDir, false);

if (hba_lines||hba_line_nums)

free_lines(&hba_lines,&hba_line_nums);

if (guc_hbafile)

{

conf_file=pstrdup(guc_hbafile);

}

{

char*confloc= (user_pgconfig_is_dir) ?user_pgconfig :DataDir;

conf_file=palloc(strlen(confloc)+strlen(CONF_FILE)+2);

sprintf(conf_file,"%s/%s",confloc,CONF_FILE);

conf_file=palloc(strlen(ConfigDir)+strlen(CONF_FILE)+2);

sprintf(conf_file,"%s/%s",ConfigDir,CONF_FILE);

}

file=AllocateFile(conf_file,"r");

if (ident_lines||ident_line_nums)

free_lines(&ident_lines,&ident_line_nums);

if (guc_identfile)

{

map_file=pstrdup(guc_identfile);

}

{

char*confloc= (user_pgconfig_is_dir) ?user_pgconfig :DataDir;

map_file= (char*)palloc(strlen(confloc)+strlen(USERMAP_FILE)+2);

sprintf(map_file,"%s/%s",confloc,USERMAP_FILE);

map_file=palloc(strlen(ConfigDir)+strlen(USERMAP_FILE)+2);

sprintf(map_file,"%s/%s",ConfigDir,USERMAP_FILE);

}

file=AllocateFile(map_file,"r");