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postmaster(1) - postmaster - PostgreSQL multiuser database server - man 1 postmaster

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POSTMASTER(1)           PostgreSQL Server Applications           POSTMASTER(1)



NAME
       postmaster - PostgreSQL multiuser database server


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

DESCRIPTION
       postmaster is the PostgreSQL multiuser database server.  In order for a
       client  application to access(2,5) a database it connects (over a network or
       locally) to a running postmaster. The postmaster then starts a separate
       server process (``postgres(1)'') to handle the connection. The postmas-
       ter also manages the communication among server processes.

       By default the postmaster starts in(1,8) the foreground and prints log  mes-
       sages to the standard error(8,n) stream. In practical applications the post-
       master(5,8) 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(1,n) 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(1,2,n), 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 section called ``Run-time Config-
       uration''  in(1,8) the documentation. You can also save typing most of these
       options by setting up a configuration file.

       -A 0|1 Enables run-time assertion checks, which is a debugging  aid  to
              detect  programming  mistakes.  This is only available if(3,n) 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(5,8) run-time  parameter.  Consult  the  section  called
              ``Run-time  Configuration''  in(1,8) the documentation for a list and
              descriptions. Most of the other command line options are in(1,8) fact
              short forms of such a parameter assignment. -c can appear multi-
              ple times to set(7,n,1 builtins) multiple parameters.

       -d debug-level
              Sets the debug level. The higher this value  is  set(7,n,1 builtins),  the  more
              debugging output is written to the server log. Values are from 1
              to 5.

       -D datadir
              Specifies the file(1,n) system location of the  data  directory.  See
              discussion above.

       -F     Disables fsync calls for performance improvement, at the risk of
              data corruption in(1,8) event of a system crash. This  option  corre-
              sponds  to  setting  fsync=false  in(1,8)  postgresql.conf.  Read the
              detailed documentation before using this!

              --fsync=true has the opposite effect of this option.

       -h hostname
              Specifies the IP host(1,5) name or address on which the postmaster is
              to  listen(1,2,7) 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(2,7,n) con-
              nections  are  accepted.  This  option  corresponds  to  setting
              tcpip_socket=true in(1,8) postgresql.conf.

              --tcpip-socket=false has the opposite effect of this option.

       -k directory
              Specifies  the  directory of the Unix-domain socket(2,7,n) on which the
              postmaster is to listen(1,2,7) 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(7,n,1 builtins)
              as high as your system will support. (Note that -B  is  required
              to  be at least twice -N. See the section called ``Managing Ker-
              nel Resources'' in(1,8) the documentation for a discussion of  system
              resource  requirements for large numbers of client connections.)

       -o extra-options
              The command line-style options specified  in(1,8)  extra-options  are
              passed  to  all server processes started by this postmaster. See
              postgres(1) for possibilities. If the option string(3,n) contains any
              spaces, the entire string(3,n) must be quoted.

       -p port
              Specifies  the  TCP/IP  port  or  local  Unix domain socket(2,7,n) file(1,n)
              extension on which the postmaster is to listen(1,2,7)  for  connections
              from  client  applications.  Defaults to the value of the PGPORT
              environment variable, or if(3,n) PGPORT is not set(7,n,1 builtins), 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(1,8)  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(8,n) to /dev/null.

              Using this switch(1,n) 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(5,8) in(1,8) the background.

              --silent-mode=false has the opposite effect of this option.

       --name=value
              Sets a named(5,8) run-time parameter; a shorter form of -c.


       Two additional command line options are available for  debugging  prob-
       lems that cause a server process to die abnormally. The ordinary strat-
       egy in(1,8) 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(2,7,2 select_tut) alternative
       behaviors of the postmaster  in(1,8)  this  situation.   Neither  option  is
       intended for use in(1,8) ordinary operation.


       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 server processes by sending the
              signal(2,7) SIGSTOP, but will not cause them to terminate. This  per-
              mits  system  programmers  to collect core dumps from all server
              processes by hand.


ENVIRONMENT
       PGCLIENTENCODING
              Default character encoding(3,n) used by  clients.  (The  clients  may
              override  this  individually.) This value can also be set(7,n,1 builtins) in(1,8) the
              configuration file.

       PGDATA Default data direction location

       PGDATESTYLE
              Default value of the DATESTYLE run-time parameter. (The  use  of
              this environment variable is deprecated.)

       PGPORT Default port (preferably set(7,n,1 builtins) in(1,8) the configuration file(1,n))

       TZ     Server time(1,2,n) zone

       others Other environment variables may be used to designate alternative
              data storage locations. See the chapter called ``Managing  Data-
              bases'' in(1,8) the documentation for more information.

DIAGNOSTICS
       A  failure  message  mentioning semget or shmget probably indicates you
       need to configure your kernel to provide  adequate  shared  memory  and
       semaphores.  For more discussion see the section called ``Managing Ker-
       nel Resouces'' in(1,8) the documentation.

              Tip: You may be able to postpone reconfiguring  your  kernel  by
              decreasing  shared_buffers  to reduce the shared memory consump-
              tion of PostgreSQL, and/or by reducing max_connections to reduce
              the semaphore consumption.


       A failure message suggesting that another postmaster is already running
       should be checked carefully, for example by using the command

       $ ps ax | grep postmaster

       or

       $ ps -ef | grep postmaster

       depending on your system. If you are certain that no conflicting  post-
       master(5,8)  is  running, you may remove the lock file(1,n) mentioned in(1,8) the mes-
       sage and try again.

       A failure message indicating inability to bind(2,n,1 builtins) to a port  may  indicate
       that  that  port is already in(1,8) use by some non-PostgreSQL process.  You
       may also get this error(8,n) if(3,n) you terminate the postmaster and immediately
       restart  it  using  the same port; in(1,8) 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(8,n) if(3,n) 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(2,5) them.

NOTES
       If at all possible, do not use SIGKILL to kill(1,2,1 builtins) the postmaster. Doing so
       will prevent postmaster from freeing the system resources (e.g., shared
       memory and semaphores) that it holds before terminating. This may cause
       problems for starting a fresh postmaster run.

       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 proper shutdown(2,8), resulting in(1,8) a
       recovery  run  during restart. The SIGHUP signal(2,7) will reload the server
       configuration files.

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

       The  --  options  will not work on FreeBSD or OpenBSD.  Use -c instead.
       This is a bug in(1,8) the affected operating systems; a  future  release  of
       PostgreSQL will provide a workaround if(3,n) this is not fixed.

EXAMPLES
       To start postmaster in(1,8) 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(7,n,1 builtins) the environment variable PGPORT:

       $ export PGPORT=1234
       $ psql


       Named run-time parameters can be set(7,n,1 builtins) in(1,8) either of these styles:

       $ postmaster -c sort_mem=1234
       $ postmaster --sort-mem=1234

       Either  form  overrides  whatever  setting  might exist for SORT_MEM in(1,8)
       postgresql.conf. Notice that underscores  in(1,8)  parameter  names  can  be
       written as either underscore or dash on the command line.

              Tip:  Except  for  short-term  experiments, it's probably better
              practice to edit the setting in(1,8) postgresql.conf than to rely  on
              a command-line switch(1,n) to set(7,n,1 builtins) a parameter.


SEE ALSO
       initdb(1), pg_ctl(1)



Application                       2003-11-02                     POSTMASTER(1)

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