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><H1
><A
NAME="APP-POSTMASTER"
><SPAN
CLASS="APPLICATION"
>postmaster</SPAN
></A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN51540"
></A
><H2
>Name</H2
>postmaster -- <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> multiuser database server</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN51544"
></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="AEN51580"
></A
><H2
>Description</H2
><P
> <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> 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
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>. The
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> 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 <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> also
manages the communication among server processes.
</P
><P
> By default the <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> starts in the
foreground and prints log messages to the standard output. In
practical applications the <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
should be started as a background process, perhaps at boot time.
</P
><P
> One <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> 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 postmaster starts it needs to know the location
of the database cluster files (<SPAN
CLASS="QUOTE"
>"data area"</SPAN
>). This is
done with the <TT
CLASS="OPTION"
>-D</TT
> invocation option or the
<TT
CLASS="ENVAR"
>PGDATA</TT
> environment variable; there is no default.
More than one postmaster process can run on a system at one time,
as 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
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="APP-POSTMASTER-OPTIONS"
></A
><H2
>Options</H2
><P
> <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> accepts the following
command line arguments. For a detailed discussion of the options
consult the <I
CLASS="CITETITLE"
>Administrator's Guide</I
>. You can
also save typing most of these options by setting up a
configuration file.
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
>-A 0|1</DT
><DD
><P
> Enables run-time assert checks, which is a debugging aid to
detect programming mistakes. This is only available if it was
enabled during compilation. If so, the default is on.
</P
></DD
><DT
>-B <TT
CLASS="REPLACEABLE"
><I
>nbuffers</I
></TT
></DT
><DD
><P
> Sets the number of shared buffers for use by the server
processes. This value defaults to 64 buffers, where each
buffer is 8 kB.
</P
></DD
><DT
>-c <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>=<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
></DT
><DD
><P
> Sets a named run-time parameter. Consult the
<I
CLASS="CITETITLE"
>Administrator's Guide</I
> for a list and
descriptions. 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
>-d <TT
CLASS="REPLACEABLE"
><I
>debug-level</I
></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
>-D <TT
CLASS="REPLACEABLE"
><I
>datadir</I
></TT
></DT
><DD
><P
> Specifies the file system location of the data directory. See
discussion above.
</P
></DD
><DT
>-F</DT
><DD
><P
> Disables <TT
CLASS="FUNCTION"
>fsync</TT
> calls for performance
improvement, at the risk of data corruption in event of a
system crash. This parameter corresponds to setting
<TT
CLASS="LITERAL"
>fsync=false</TT
> in <TT
CLASS="FILENAME"
>postgresql.conf</TT
>. 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
>-h <TT
CLASS="REPLACEABLE"
><I
>hostname</I
></TT
></DT
><DD
><P
> Specifies the TCP/IP host name or address on which the
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> is to listen for
connections from client applications. Defaults to
listening on all configured addresses (including
<SPAN
CLASS="SYSTEMITEM"
>localhost</SPAN
>).
</P
></DD
><DT
>-i</DT
><DD
><P
> Allows clients to connect via TCP/IP (Internet domain)
connections. Without this option, only local Unix domain
socket connections are accepted. This option corresponds
to setting <TT
CLASS="LITERAL"
>tcpip_socket=true</TT
> in <TT
CLASS="FILENAME"
>postgresql.conf</TT
>.
</P
><P
> <TT
CLASS="OPTION"
>--tcpip_socket=false</TT
> has the opposite
effect of this option.
</P
></DD
><DT
>-k <TT
CLASS="REPLACEABLE"
><I
>directory</I
></TT
></DT
><DD
><P
> Specifies the directory of the Unix-domain socket on which the
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> 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
>-l</DT
><DD
><P
> Enables secure connections using SSL. The <TT
CLASS="OPTION"
>-i</TT
>
option is also required. You must have compiled with SSL
enabled to use this option.
</P
></DD
><DT
>-N <TT
CLASS="REPLACEABLE"
><I
>max-connections</I
></TT
></DT
><DD
><P
> Sets the maximum number of client connections that this
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> 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 the <I
CLASS="CITETITLE"
>Administrator's
Guide</I
> for a discussion of system resource requirements
for large numbers of client connections.)
</P
></DD
><DT
>-o <TT
CLASS="REPLACEABLE"
><I
>extra-options</I
></TT
></DT
><DD
><P
> The command line-style options specified in <TT
CLASS="REPLACEABLE"
><I
>extra-options</I
></TT
> are passed to
all backend server processes started by this
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>. 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
>-p <TT
CLASS="REPLACEABLE"
><I
>port</I
></TT
></DT
><DD
><P
> Specifies the TCP/IP port or local Unix domain socket file
extension on which the <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
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
>-S</DT
><DD
><P
> Specifies that the <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
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 <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> in the background.
</P
><P
> <TT
CLASS="OPTION"
>--silent_mode=false</TT
> has the opposite effect
of this option.
</P
></DD
><DT
>--<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>=<TT
CLASS="REPLACEABLE"
><I
>value</I
></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 backend to die abnormally. These options
control the behavior of the <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
in this situation, and <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>neither option is intended for
use in ordinary operation</I
></SPAN
>.
</P
><P
> The ordinary strategy for this situation is to notify all other
backends that they must terminate and then reinitialize the shared
memory and semaphores. This is because an errant backend could
have corrupted some shared state before terminating.
</P
><P
> These special-case options are:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
>-n</DT
><DD
><P
> <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
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
>-s</DT
><DD
><P
> <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
will stop all other backend 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 backend processes by hand.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51728"
></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 direction location
</P
></DD
><DT
><TT
CLASS="ENVAR"
>PGDATASTYLE</TT
></DT
><DD
><P
> Default value of the <TT
CLASS="LITERAL"
>datestyle</TT
> 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
><DT
>others</DT
><DD
><P
> Other environment variables may be used to designate alternative
data storage locations. See the <I
CLASS="CITETITLE"
>Administrator's
Guide</I
> for more information.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51762"
></A
><H2
>Diagnostics</H2
><P
> <P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="COMPUTEROUTPUT"
>semget: No space left on device
</TT
></DT
><DD
><P
> If you see this message, you should run the
<SPAN
CLASS="APPLICATION"
>ipcclean</SPAN
>
command. After doing so, try starting
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
again. If this still doesn't work, you probably need to configure
your kernel for shared memory and semaphores as described in the
installation notes. If you run multiple instances of
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
on a single host, or have a kernel with particularly small shared memory
and/or semaphore limits, you may have to reconfigure your kernel to increase
its shared memory or semaphore parameters.
<DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> You may be able to postpone
reconfiguring your kernel by decreasing <TT
CLASS="OPTION"
>-B</TT
> to reduce
the shared memory consumption of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>,
and/or by reducing <TT
CLASS="OPTION"
>-N</TT
> to reduce the semaphore
consumption.
</P
></BLOCKQUOTE
></DIV
>
</P
></DD
><DT
><TT
CLASS="COMPUTEROUTPUT"
>StreamServerPort: cannot bind to port
</TT
></DT
><DD
><P
> If you see this message, you should make certain that there is no
other <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
process already running on the same port number. The easiest way to
determine this is by using the command
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>ps ax | grep postmaster</B
></TT
></PRE
><P>
or
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>ps -e | grep postmaster</B
></TT
></PRE
><P>
depending on your system.
</P
><P
> If you
are sure that no other
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
processes are running and you still get this error, try specifying a
different port using the
<TT
CLASS="LITERAL"
>-p</TT
>
option. You may also get this error if you terminate the
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
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 <I
CLASS="FIRSTTERM"
>trusted</I
>
and only permit the Unix superuser to access them.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51796"
></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
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>. This will prevent
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> from freeing the system
resources (e.g., shared memory and semaphores) that it holds before
terminating.
</P
><P
> To terminate the <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> 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.
</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 <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
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 <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> in the background
using default values, type:
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>nohup postmaster >logfile 2>&1 </dev/null &</B
></TT
></PRE
><P>
</P
><P
> To start <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> with a specific
port:
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>postmaster -p 1234</B
></TT
></PRE
><P>
This command will start up <SPAN
CLASS="APPLICATION"
>postmaster</SPAN
>
communicating through the port 1234. In order to connect to this
<SPAN
CLASS="APPLICATION"
>postmaster</SPAN
> using <SPAN
CLASS="APPLICATION"
>psql</SPAN
>, you would need to
run it as
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>psql -p 1234</B
></TT
></PRE
><P>
or set the environment variable <TT
CLASS="ENVAR"
>PGPORT</TT
>:
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>export PGPORT=1234</B
></TT
>
<TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>psql</B
></TT
></PRE
><P>
</P
><P
> Named run-time parameters can be set in either of these styles:
</P><PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>postmaster -c sort_mem=1234</B
></TT
>
<TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>postmaster --sort-mem=1234</B
></TT
></PRE
><P>
Either form overrides whatever setting might exist for <TT
CLASS="LITERAL"
>sort_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
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN51852"
></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
>
</P
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