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POSTMASTER(1)		PostgreSQL Server Applications		 POSTMASTER(1)

NAME
       postmaster - PostgreSQL multi-user database server

SYNOPSIS
       postmaster  [  -A   {  0 | 1 } ] [ -B nbuffers ] [ -c name=value ] [ -d
       debug-level ] [ -D datadir ] [ -F ] [ -h hostname ] [ -i ] [ -k	direc‐
       tory ] [ -l ] [ -N max-connections ] [ -o extra-options ] [ -p port ] [
       -S ] [ -n | -s ]

DESCRIPTION
       postmaster is the PostgreSQL multi-user database server.	 In order  for
       a  client  application to access a database it connects (over a network
       or locally) to a running postmaster. The postmaster then starts a sepa‐
       rate  server  process  (``postgres(1)'')	 to handle the connection. The
       postmaster also manages the communication among server processes.

       By default the postmaster starts in the foreground and prints log  mes‐
       sages  to the standard output. In practical applications the postmaster
       should be started as a background process, perhaps at boot time.

       One postmaster always manages the data from exactly one database	 clus‐
       ter.  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 (``data area''). This
       is done with the -D invocation option or the PGDATA  environment	 vari‐
       able; 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 dif‐
       ferent  communication  ports  (see  below). A data area is created with
       initdb(1).

   OPTIONS
       postmaster accepts the following command line arguments. For a detailed
       discussion  of  the  options consult the Administrator's Guide. You can
       also save typing most of these options by setting  up  a	 configuration
       file.

       -A 0|1 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.

       -B nbuffers
	      Sets  the	 number	 of  shared buffers for use by the server pro‐
	      cesses. This value defaults to 64 buffers, where each buffer  is
	      8 kB.

       -c name=value
	      Sets  a  named  run-time	parameter. Consult the Administrator's
	      Guide for a list and descriptions. Most  of  the	other  command
	      line options are in fact short forms of such a parameter assign‐
	      ment.

	      On some systems it is also possible  to  equivalently  use  GNU-
	      style long options in the form --name=value.

       -d debug-level
	      Sets  the	 debug	level.	The higher this value is set, the more
	      debugging output is written to the server log. The default is 0,
	      which means no debugging. Values up to 4 make sense.

       -D datadir
	      Specifies	 the  file  system location of the data directory. See
	      discussion above.

       -F     Disables fsync calls for performance improvement at the risk  of
	      data  corruption.	 Read  the detailed documentation before using
	      this!

       -h hostname
	      Specifies the TCP/IP hostname or address on which the postmaster
	      is  to listen for connections from client applications. Defaults
	      to listening on all configured addresses (including localhost).

       -i     Allows clients to connect via TCP/IP (Internet  domain)  connec‐
	      tions.  Without  this option, only local Unix domain socket con‐
	      nections are accepted.

       -k directory
	      Specifies the directory of the Unix-domain socket on  which  the
	      postmaster  is  to  listen  for connections from client applica‐
	      tions. The default is normally /tmp, but can be changed at build
	      time.

       -l     Enables  secure  connections  using  SSL.	 The -i option is also
	      required. You must have compiled with SSL enabled	 to  use  this
	      option.

       -N max-connections
	      Sets the maximum number of client connections that this postmas‐
	      ter will accept. By default, this value is 32, but it can be set
	      as high as 1024 if your system will support that many processes.
	      (Note that -B is required to be at least twice -N.)

       -o extra-options
	      The command line-style options specified	in  extra-options  are
	      passed  to all backend server processes started by this postmas‐
	      ter. See postgres(1) for possibilities.  If  the	option	string
	      contains any spaces, the entire string must be quoted.

       -p port
	      Specifies	 the  TCP/IP  port  or	local  Unix domain socket file
	      extension on which the postmaster is to listen  for  connections
	      from  client  applications.  Defaults to the value of the PGPORT
	      environment variable, or if PGPORT 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 PGPORT.

       -S     Specifies that the postmaster process should start up in	silent
	      mode.  That  is,	it will disassociate from the user's (control‐
	      ling) terminal, start its own process group,  and	 redirect  its
	      standard output and standard error to /dev/null.

	      Using this switch discards all logging output, which is probably
	      not what you want, since it makes it  very  difficult  to	 trou‐
	      bleshoot problems. See below for a better way to start the post‐
	      master in the background.

       Two additional command line options are available for  debugging	 prob‐
       lems  that cause a backend to die abnormally. These options control the
       behavior of the postmaster in this situation,  and  neither  option  is
       intended for use in ordinary operation.

       The  ordinary  strategy for this situation is to notify all other back‐
       ends 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.

       These special-case options are:

       -n     postmaster will  not  reinitialize  shared  data	structures.  A
	      knowledgeable system programmer can then use a debugger to exam‐
	      ine shared memory and semaphore state.

       -s     postmaster will stop all other backend processes by sending  the
	      signal  SIGSTOP, but will not cause them to terminate. This per‐
	      mits system programmers to collect core dumps from  all  backend
	      processes by hand.

   OUTPUTS
       semget: No space left on device
	      If  you  see  this message, you should run the ipcclean command.
	      After doing so, try starting postmaster  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 postmaster 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.

	      Tip: You may be able to postpone reconfiguring  your  kernel  by
	      decreasing  -B  to  reduce  Postgres' shared memory consumption,
	      and/or by reducing -N to reduce Postgres' semaphore consumption.

       StreamServerPort: cannot bind to port
	      If you see this message, you should make certain that  there  is
	      no  other	 postmaster  process  already running on the same port
	      number. The easiest way to determine this is by using  the  com‐
	      mand

	      $ ps ax | grep postmaster

	      or

	      $ ps -e | grep postmaster

	      depending on your system.

	      If  you  are sure that no other postmaster processes are running
	      and you still get this error, try specifying  a  different  port
	      using  the  -p option. You may also get this error if you termi‐
	      nate the postmaster 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 trusted
	      and only permit the Unix superuser to access them.

NOTES
       If at all possible, do not use SIGKILL to  kill	the  postmaster.  This
       will prevent postmaster from freeing the system resources (e.g., shared
       memory and semaphores) that it holds before terminating.

       To terminate the postmaster normally, the signals SIGTERM,  SIGINT,  or
       SIGQUIT	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 lengthy shutdown, resulting in
       a recovery run during restart.

       The utility command pg_ctl(1) can be used to start and  shut  down  the
       postmaster safely and comfortably.

USAGE
       To start postmaster in the background using default values, type:

       $ nohup postmaster >logfile 2>&1 </dev/null &

       To start postmaster with a specific port:

       $ postmaster -p 1234

       This  command  will  start up postmaster communicating through the port
       1234. In order to connect to this postmaster using psql, you would need
       to run it as

       $ psql -p 1234

       or set the environment variable PGPORT:

       $ export PGPORT=1234
       $ psql

Application			  2000-12-25			 POSTMASTER(1)
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