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><H1
><A
NAME="APP-POSTMASTER"
></A
><SPAN
CLASS="APPLICATION"
>postmaster</SPAN
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN51255"
></A
><H2
>Name</H2
>postmaster -- <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> multiuser database server</DIV
><A
NAME="AEN51259"
></A
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN51261"
></A
><H2
>Synopsis</H2
><P
><TT
CLASS="COMMAND"
>postmaster</TT
> [-A 0 | 1 ] [-B <TT
CLASS="REPLACEABLE"
><I
>nbuffers</I
></TT
>] [-c <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>=<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
>] [-d <TT
CLASS="REPLACEABLE"
><I
>debug-level</I
></TT
>] [-D <TT
CLASS="REPLACEABLE"
><I
>datadir</I
></TT
>] [-F] [-h <TT
CLASS="REPLACEABLE"
><I
>hostname</I
></TT
>] [-i] [-k <TT
CLASS="REPLACEABLE"
><I
>directory</I
></TT
>] [-l] [-N <TT
CLASS="REPLACEABLE"
><I
>max-connections</I
></TT
>] [-o <TT
CLASS="REPLACEABLE"
><I
>extra-options</I
></TT
>] [-p <TT
CLASS="REPLACEABLE"
><I
>port</I
></TT
>] [-S] [--<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>=<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
>] [-n | -s]</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51297"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>postmaster</TT
> is the
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> multiuser database server.
In order for a client application to access a database it connects
(over a network or locally) to a running
<TT
CLASS="COMMAND"
>postmaster</TT
>. The
<TT
CLASS="COMMAND"
>postmaster</TT
> then starts a separate server
process (<SPAN
CLASS="QUOTE"
>"<A
HREF="app-postgres.html"
><SPAN
CLASS="APPLICATION"
>postgres</SPAN
></A
>"</SPAN
>) to handle
the connection. The <TT
CLASS="COMMAND"
>postmaster</TT
> also
manages the communication among server processes.
</P
><P
> By default the <TT
CLASS="COMMAND"
>postmaster</TT
> starts in the
foreground and prints log messages to the standard error stream. In
practical applications the <TT
CLASS="COMMAND"
>postmaster</TT
>
should be started as a background process, perhaps at boot time.
</P
><P
> One <TT
CLASS="COMMAND"
>postmaster</TT
> 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 (the <SPAN
CLASS="QUOTE"
>"data area"</SPAN
>).
More than one <TT
CLASS="COMMAND"
>postmaster</TT
> process can run on a system
at one time, so long as they use different data areas and different
communication ports (see below). A data area is created with <A
HREF="app-initdb.html"
>initdb</A
>.
</P
><P
> When the <TT
CLASS="COMMAND"
>postmaster</TT
> starts it needs
to know the location of the data area.
The location must be specified by the <TT
CLASS="OPTION"
>-D</TT
> option
or the <TT
CLASS="ENVAR"
>PGDATA</TT
> environment variable; there is no default.
Typically, <TT
CLASS="OPTION"
>-D</TT
> or <TT
CLASS="ENVAR"
>PGDATA</TT
> points
directly to the data area directory created by <SPAN
CLASS="APPLICATION"
>initdb</SPAN
>.
Other possible file layouts are discussed in
<A
HREF="runtime-config.html#RUNTIME-CONFIG-FILE-LOCATIONS"
>Section 16.4.1</A
>.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="APP-POSTMASTER-OPTIONS"
></A
><H2
>Options</H2
><P
> <TT
CLASS="COMMAND"
>postmaster</TT
> accepts the following
command line arguments. For a detailed discussion of the options
consult <A
HREF="runtime-config.html"
>Section 16.4</A
>. You can also save typing most of these
options by setting up a configuration file.
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="OPTION"
>-A 0|1</TT
></DT
><DD
><P
> Enables run-time assertion checks, which is a debugging aid to
detect programming mistakes. This option is only available if
assertions were enabled when <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> was
compiled. If so, the default is on.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-B <TT
CLASS="REPLACEABLE"
><I
>nbuffers</I
></TT
></TT
></DT
><DD
><P
> Sets the number of shared buffers for use by the server
processes. The default value of this parameter is chosen
automatically by <SPAN
CLASS="APPLICATION"
>initdb</SPAN
>; refer to <A
HREF="runtime-config.html#RUNTIME-CONFIG-RESOURCE-MEMORY"
>Section 16.4.3.1</A
> for more information.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-c <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>=<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
></TT
></DT
><DD
><P
> Sets a named run-time parameter. The configuration parameters
supported by <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> are
described in <A
HREF="runtime-config.html"
>Section 16.4</A
>. Most of the
other command line options are in fact short forms of such a
parameter assignment. <TT
CLASS="OPTION"
>-c</TT
> can appear multiple times
to set multiple parameters.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-d <TT
CLASS="REPLACEABLE"
><I
>debug-level</I
></TT
></TT
></DT
><DD
><P
> Sets the debug level. The higher this value is set, the more
debugging output is written to the server log. Values are from
1 to 5.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-D <TT
CLASS="REPLACEABLE"
><I
>datadir</I
></TT
></TT
></DT
><DD
><P
> Specifies the file system location of the data directory or
configuration file(s). See
<A
HREF="runtime-config.html#RUNTIME-CONFIG-FILE-LOCATIONS"
>Section 16.4.1</A
> for details.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-F</TT
></DT
><DD
><P
> Disables <CODE
CLASS="FUNCTION"
>fsync</CODE
> calls for improved
performance, at the risk of data corruption in the event of a
system crash. Specifying this option is equivalent to
disabling the <A
HREF="runtime-config.html#GUC-FSYNC"
>fsync</A
> configuration
parameter. Read the detailed documentation before using this!
</P
><P
> <TT
CLASS="OPTION"
>--fsync=true</TT
> has the opposite effect
of this option.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-h <TT
CLASS="REPLACEABLE"
><I
>hostname</I
></TT
></TT
></DT
><DD
><P
> Specifies the IP host name or address on which the
<TT
CLASS="COMMAND"
>postmaster</TT
> is to listen for TCP/IP
connections from client applications. The value can also be a
comma-separated list of addresses, or <TT
CLASS="LITERAL"
>*</TT
> to specify
listening on all available interfaces. An empty value
specifies not listening on any IP addresses, in which case
only Unix-domain sockets can be used to connect to the
<TT
CLASS="COMMAND"
>postmaster</TT
>. Defaults to listening only on
<SPAN
CLASS="SYSTEMITEM"
>localhost</SPAN
>.
Specifying this option is equivalent to setting the <A
HREF="runtime-config.html#GUC-LISTEN-ADDRESSES"
>listen_addresses</A
> configuration parameter.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-i</TT
></DT
><DD
><P
> Allows remote clients to connect via TCP/IP (Internet domain)
connections. Without this option, only local connections are
accepted. This option is equivalent to setting
<TT
CLASS="VARNAME"
>listen_addresses</TT
> to <TT
CLASS="LITERAL"
>*</TT
> in
<TT
CLASS="FILENAME"
>postgresql.conf</TT
> or via <TT
CLASS="OPTION"
>-h</TT
>.
</P
><P
> This option is deprecated since it does not allow access to the
full functionality of <A
HREF="runtime-config.html#GUC-LISTEN-ADDRESSES"
>listen_addresses</A
>.
It's usually better to set <TT
CLASS="VARNAME"
>listen_addresses</TT
> directly.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-k <TT
CLASS="REPLACEABLE"
><I
>directory</I
></TT
></TT
></DT
><DD
><P
> Specifies the directory of the Unix-domain socket on which the
<TT
CLASS="COMMAND"
>postmaster</TT
> is to listen for
connections from client applications. The default is normally
<TT
CLASS="FILENAME"
>/tmp</TT
>, but can be changed at build time.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-l</TT
></DT
><DD
><P
> Enables secure connections using <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
>.
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> must have been compiled with
support for <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> for this option to be
available. For more information on using <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
>,
refer to <A
HREF="ssl-tcp.html"
>Section 16.8</A
>.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-N <TT
CLASS="REPLACEABLE"
><I
>max-connections</I
></TT
></TT
></DT
><DD
><P
> Sets the maximum number of client connections that this
<TT
CLASS="COMMAND"
>postmaster</TT
> will accept. By
default, this value is 32, but it can be set as high as your
system will support. (Note that
<TT
CLASS="OPTION"
>-B</TT
> is required to be at least twice
<TT
CLASS="OPTION"
>-N</TT
>. See <A
HREF="kernel-resources.html"
>Section 16.5</A
> for a discussion of
system resource requirements for large numbers of client
connections.) Specifying this option is equivalent to setting the
<A
HREF="runtime-config.html#GUC-MAX-CONNECTIONS"
>max_connections</A
> configuration parameter.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-o <TT
CLASS="REPLACEABLE"
><I
>extra-options</I
></TT
></TT
></DT
><DD
><P
> The command line-style options specified in <TT
CLASS="REPLACEABLE"
><I
>extra-options</I
></TT
> are passed to
all server processes started by this
<TT
CLASS="COMMAND"
>postmaster</TT
>. See <A
HREF="app-postgres.html"
><SPAN
CLASS="APPLICATION"
>postgres</SPAN
></A
> for possibilities. If the option
string contains any spaces, the entire string must be quoted.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-p <TT
CLASS="REPLACEABLE"
><I
>port</I
></TT
></TT
></DT
><DD
><P
> Specifies the TCP/IP port or local Unix domain socket file
extension on which the <TT
CLASS="COMMAND"
>postmaster</TT
>
is to listen for connections from client applications.
Defaults to the value of the <TT
CLASS="ENVAR"
>PGPORT</TT
> environment
variable, or if <TT
CLASS="ENVAR"
>PGPORT</TT
> is not set, then
defaults to the value established during compilation (normally
5432). If you specify a port other than the default port,
then all client applications must specify the same port using
either command-line options or <TT
CLASS="ENVAR"
>PGPORT</TT
>.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-S</TT
></DT
><DD
><P
> Specifies that the <TT
CLASS="COMMAND"
>postmaster</TT
>
process should start up in silent mode. That is, it will
disassociate from the user's (controlling) terminal, start its
own process group, and redirect its standard output and
standard error to <TT
CLASS="FILENAME"
>/dev/null</TT
>.
</P
><P
> Using this switch discards all logging output, which is
probably not what you want, since it makes it very difficult
to troubleshoot problems. See below for a better way to start
the <TT
CLASS="COMMAND"
>postmaster</TT
> in the background.
</P
><P
> <TT
CLASS="OPTION"
>--silent-mode=false</TT
> has the opposite effect
of this option.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>=<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
></TT
></DT
><DD
><P
> Sets a named run-time parameter; a shorter form of
<TT
CLASS="OPTION"
>-c</TT
>.
</P
></DD
></DL
></DIV
><P>
</P
><P
> Two additional command line options are available for debugging
problems that cause a server process to die abnormally. The
ordinary strategy in this situation is to notify all other server
processes that they must terminate and then reinitialize the
shared memory and semaphores. This is because an errant server
process could have corrupted some shared state before terminating.
These options select alternative behaviors of the
<TT
CLASS="COMMAND"
>postmaster</TT
> in this situation.
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Neither option is intended for use in ordinary
operation.</I
></SPAN
>
</P
><P
> </P
><P
> These special-case options are:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="OPTION"
>-n</TT
></DT
><DD
><P
> <TT
CLASS="COMMAND"
>postmaster</TT
>
will not reinitialize shared data structures. A knowledgeable system
programmer can then use a debugger
to examine shared memory and semaphore state.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-s</TT
></DT
><DD
><P
> <TT
CLASS="COMMAND"
>postmaster</TT
>
will stop all other server processes by sending the signal
<TT
CLASS="LITERAL"
>SIGSTOP</TT
>,
but will not cause them to terminate. This permits system programmers
to collect core dumps from all server processes by hand.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51484"
></A
><H2
>Environment</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="ENVAR"
>PGCLIENTENCODING</TT
></DT
><DD
><P
> Default character encoding used by clients. (The clients may
override this individually.) This value can also be set in the
configuration file.
</P
></DD
><DT
><TT
CLASS="ENVAR"
>PGDATA</TT
></DT
><DD
><P
> Default data directory location
</P
></DD
><DT
><TT
CLASS="ENVAR"
>PGDATESTYLE</TT
></DT
><DD
><P
> Default value of the <A
HREF="runtime-config.html#GUC-DATESTYLE"
>DateStyle</A
> run-time
parameter. (The use of this environment variable is deprecated.)
</P
></DD
><DT
><TT
CLASS="ENVAR"
>PGPORT</TT
></DT
><DD
><P
> Default port (preferably set in the configuration file)
</P
></DD
><DT
><TT
CLASS="ENVAR"
>TZ</TT
></DT
><DD
><P
> Server time zone
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51513"
></A
><H2
>Diagnostics</H2
><P
> A failure message mentioning <TT
CLASS="LITERAL"
>semget</TT
> or <TT
CLASS="LITERAL"
>shmget</TT
>
probably indicates you need to configure your kernel to provide adequate
shared memory and semaphores. For more discussion see <A
HREF="kernel-resources.html"
>Section 16.5</A
>.
</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> You may be able to postpone reconfiguring your kernel by
decreasing <A
HREF="runtime-config.html#GUC-SHARED-BUFFERS"
>shared_buffers</A
> to reduce the
shared memory consumption of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>, and/or
by reducing <A
HREF="runtime-config.html#GUC-MAX-CONNECTIONS"
>max_connections</A
> to reduce the
semaphore consumption.
</P
></BLOCKQUOTE
></DIV
><P
> A failure message suggesting that another postmaster is already running
should be checked carefully, for example by using the command
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>ps ax | grep postmaster</KBD
></PRE
><P>
or
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>ps -ef | grep postmaster</KBD
></PRE
><P>
depending on your system. If you are certain that no conflicting
postmaster is running, you may remove the lock file mentioned in the
message and try again.
</P
><P
> A failure message indicating inability to bind to a port may
indicate that that port is already in use by some
non-<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> process. You may also
get this error if you terminate the <TT
CLASS="COMMAND"
>postmaster</TT
>
and immediately restart it using the same port; in this case, you
must simply wait a few seconds until the operating system closes
the port before trying again. Finally, you may get this error if
you specify a port number that your operating system considers to
be reserved. For example, many versions of Unix consider port
numbers under 1024 to be <SPAN
CLASS="QUOTE"
>"trusted"</SPAN
> and only permit
the Unix superuser to access them.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51535"
></A
><H2
>Notes</H2
><P
> If at all possible, <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>do not</I
></SPAN
> use
<TT
CLASS="LITERAL"
>SIGKILL</TT
> to kill the
<TT
CLASS="COMMAND"
>postmaster</TT
>. Doing so will prevent
<TT
CLASS="COMMAND"
>postmaster</TT
> from freeing the system
resources (e.g., shared memory and semaphores) that it holds before
terminating. This may cause problems for starting a fresh
<TT
CLASS="COMMAND"
>postmaster</TT
> run.
</P
><P
> To terminate the <TT
CLASS="COMMAND"
>postmaster</TT
> normally,
the signals <TT
CLASS="LITERAL"
>SIGTERM</TT
>, <TT
CLASS="LITERAL"
>SIGINT</TT
>,
or <TT
CLASS="LITERAL"
>SIGQUIT</TT
> can be used. The first will wait for
all clients to terminate before quitting, the second will
forcefully disconnect all clients, and the third will quit
immediately without proper shutdown, resulting in a recovery run
during restart. The <TT
CLASS="LITERAL"
>SIGHUP</TT
> signal will
reload the server configuration files.
</P
><P
> The utility command <A
HREF="app-pg-ctl.html"
><SPAN
CLASS="APPLICATION"
>pg_ctl</SPAN
></A
> can be used to
start and shut down the <TT
CLASS="COMMAND"
>postmaster</TT
>
safely and comfortably.
</P
><P
> The <TT
CLASS="OPTION"
>--</TT
> options will not work on <SPAN
CLASS="SYSTEMITEM"
>FreeBSD</SPAN
> or <SPAN
CLASS="SYSTEMITEM"
>OpenBSD</SPAN
>.
Use <TT
CLASS="OPTION"
>-c</TT
> instead. This is a bug in the affected operating
systems; a future release of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
will provide a workaround if this is not fixed.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="APP-POSTMASTER-EXAMPLES"
></A
><H2
>Examples</H2
><P
> To start <TT
CLASS="COMMAND"
>postmaster</TT
> in the background
using default values, type:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>nohup postmaster >logfile 2>&1 </dev/null &</KBD
></PRE
><P>
</P
><P
> To start <TT
CLASS="COMMAND"
>postmaster</TT
> with a specific
port:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>postmaster -p 1234</KBD
></PRE
><P>
This command will start up <TT
CLASS="COMMAND"
>postmaster</TT
>
communicating through the port 1234. In order to connect to this
<TT
CLASS="COMMAND"
>postmaster</TT
> using <SPAN
CLASS="APPLICATION"
>psql</SPAN
>, you would need to
run it as
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>psql -p 1234</KBD
></PRE
><P>
or set the environment variable <TT
CLASS="ENVAR"
>PGPORT</TT
>:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>export PGPORT=1234</KBD
>
<SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>psql</KBD
></PRE
><P>
</P
><P
> Named run-time parameters can be set in either of these styles:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>postmaster -c work_mem=1234</KBD
>
<SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>postmaster --work-mem=1234</KBD
></PRE
><P>
Either form overrides whatever setting might exist for <TT
CLASS="VARNAME"
>work_mem</TT
>
in <TT
CLASS="FILENAME"
>postgresql.conf</TT
>. Notice that underscores in parameter
names can be written as either underscore or dash on the command line.
</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> Except for short-term experiments,
it's probably better practice to edit the setting in
<TT
CLASS="FILENAME"
>postgresql.conf</TT
> than to rely on a command-line switch
to set a parameter.
</P
></BLOCKQUOTE
></DIV
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></A
><H2
>See Also</H2
><P
> <A
HREF="app-initdb.html"
>initdb</A
>,
<A
HREF="app-pg-ctl.html"
><SPAN
CLASS="APPLICATION"
>pg_ctl</SPAN
></A
>
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