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NAME

       postgres - PostgreSQL database server

SYNOPSIS

       postgres [ option... ]

DESCRIPTION

       postgres  is  the  PostgreSQL  database  server.  In order for a client
       application to access  a  database  it  connects  (over  a  network  or
       locally)  to  a  running postgres instance.  The postgres instance then
       starts a separate server process to handle the connection.

       One postgres instance always manages the data of exactly  one  database
       cluster. A database cluster is a collection of databases that is stored
       at a common file system location (the ‘‘data  area’’).  More  than  one
       postgres  instance can run on a system at one time, so long as they use
       different data areas and different  communication  ports  (see  below).
       When  postgres  starts  it needs to know the location of the data area.
       The location  must  be  specified  by  the  -D  option  or  the  PGDATA
       environment  variable;  there  is  no  default. Typically, -D or PGDATA
       points directly to the data area directory created by initdb(1).  Other
       possible file layouts are discussed in in the documentation.

       By default postgres starts in the foreground and prints log messages to
       the standard error stream. In practical applications postgres should be
       started as a background process, perhaps at boot time.

       The  postgres  command  can  also  be  called  in single-user mode. The
       primary use  for  this  mode  is  during  bootstrapping  by  initdb(1).
       Sometimes  it is used for debugging or disaster recovery (but note that
       running a single-user server is not truly suitable  for  debugging  the
       server,  since no realistic interprocess communication and locking will
       happen).  When invoked in single-user mode from the shell, the user can
       enter  queries  and the results will be printed to the screen, but in a
       form that is more useful for developers than end users. In the  single-
       user  mode,  the  session  user  will be set to the user with ID 1, and
       implicit superuser powers are granted to this user.  This user does not
       actually have to exist, so the single-user mode can be used to manually
       recover from certain kinds of accidental damage to the system catalogs.

OPTIONS

       postgres  accepts  the following command-line arguments. For a detailed
       discussion of the options consult in the documentation.  You  can  save
       typing  most  of these options by setting up a configuration file. Some
       (safe) options can also  be  set  from  the  connecting  client  in  an
       application-dependent  way to apply only for that session. For example,
       if the environment variable PGOPTIONS is set, then libpq-based  clients
       will  pass  that  string  to  the  server,  which  will interpret it as
       postgres command-line options.

   GENERAL PURPOSE
       -A 0|1 Enables run-time assertion checks, which is a debugging  aid  to
              detect  programming  mistakes.  This option is only available if
              assertions were enabled when PostgreSQL was compiled. If so, the
              default is on.

       -B nbuffers
              Sets  the  number  of  shared  buffers  for  use  by  the server
              processes.  The  default  value  of  this  parameter  is  chosen
              automatically  by  initdb.  Specifying this option is equivalent
              to setting the shared_buffers configuration parameter.

       -c name=value
              Sets a named run-time parameter.  The  configuration  parameters
              supported  by  PostgreSQL are described in in the documentation.
              Most of the other command line options are in fact  short  forms
              of  such a parameter assignment. -c can appear multiple times to
              set multiple parameters.

       -d debug-level
              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. It is also possible to pass -d 0 for a  specific  session,
              which  will  prevent the server log level of the parent postgres
              process from being propagated to this session.

       -D datadir
              Specifies the file system location  of  the  data  directory  or
              configuration file(s). See in the documentation for details.

       -e     Sets  the  default  date  style  to  ‘‘European’’,  that  is DMY
              ordering of input date fields. This also causes the  day  to  be
              printed before the month in certain date output formats.  See in
              the documentation for more information.

       -F     Disables fsync 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  fsync  configuration
              parameter. Read the detailed documentation before using this!

       -h hostname
              Specifies  the  IP  host name or address on which postgres is to
              listen for TCP/IP  connections  from  client  applications.  The
              value  can  also be a comma-separated list of addresses, or * 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  server.
              Defaults to listening only on localhost.  Specifying this option
              is equivalent  to  setting  the  listen_addresses  configuration
              parameter.

       -i     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 listen_addresses
              to * in postgresql.conf or via -h.

              This option is deprecated since it does not allow access to  the
              full  functionality of listen_addresses.  It’s usually better to
              set listen_addresses directly.

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

       -l     Enables secure connections using SSL.  PostgreSQL must have been
              compiled with support for SSL for this option to  be  available.
              For   more   information   on   using   SSL,  refer  to  in  the
              documentation.

       -N max-connections
              Sets the maximum number of client connections that  this  server
              will  accept.  The  default  value  of  this parameter is chosen
              automatically by initdb.  Specifying this option  is  equivalent
              to setting the max_connections configuration parameter.

       -o extra-options
              The  command-line-style  options  specified in extra-options are
              passed to all server processes started by this postgres process.
              If the option string contains any spaces, the entire string must
              be quoted.

              The use of this option is obsolete; all command-line options for
              server  processes  can  be  specified  directly  on the postgres
              command line.

       -p port
              Specifies the TCP/IP port  or  local  Unix  domain  socket  file
              extension  on  which  postgres 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     Print  time  information and other statistics at the end of each
              command.  This is useful for benchmarking or for use  in  tuning
              the number of buffers.

       -S work-mem
              Specifies  the amount of memory to be used by internal sorts and
              hashes  before  resorting  to  temporary  disk  files.  See  the
              description  of  the  work_mem configuration parameter in in the
              documentation.

       --name=value
              Sets a named run-time parameter; a shorter form of -c.

       --describe-config
              This  option  dumps  out  the  server’s  internal  configuration
              variables,  descriptions,  and  defaults  in  tab-delimited COPY
              format.  It is designed  primarily  for  use  by  administration
              tools.

   SEMI-INTERNAL OPTIONS
       The  options described here are used mainly for debugging purposes, and
       in some cases to assist with recovery of  severely  damaged  databases.
       There  should  be no reason to use them in a production database setup.
       They are listed here only for  use  by  PostgreSQL  system  developers.
       Furthermore,  these  options  might  change  or  be removed in a future
       release without notice.

       -f { s | i | m | n | h }
              Forbids the use of particular scan and join  methods:  s  and  i
              disable sequential and index scans respectively, while n, m, and
              h disable nested-loop, merge and hash joins respectively.

              Neither sequential scans nor nested-loop joins can  be  disabled
              completely;  the  -fs  and  -fn  options  simply  discourage the
              optimizer from using those  plan  types  if  it  has  any  other
              alternative.

       -n     This  option  is  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.  This  option
              specifies  that  postgres  will  not  reinitialize  shared  data
              structures. A knowledgeable system programmer  can  then  use  a
              debugger to examine shared memory and semaphore state.

       -O     Allows  the  structure  of system tables to be modified. This is
              used by initdb.

       -P     Ignore system indexes when  reading  system  tables  (but  still
              update  the  indexes  when modifying the tables). This is useful
              when recovering from damaged system indexes.

       -t pa[rser] | pl[anner] | e[xecutor]
              Print timing statistics for each query relating to each  of  the
              major  system  modules. This option cannot be used together with
              the -s option.

       -T     This option is  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. This option
              specifies that postgres will stop all other server processes  by
              sending   the  signal  SIGSTOP,  but  will  not  cause  them  to
              terminate. This permits system programmers to collect core dumps
              from all server processes by hand.

       -v protocol
              Specifies the version number of the frontend/backend protocol to
              be used for a particular session. This option  is  for  internal
              use only.

       -W seconds
              A delay of this many seconds occurs when a new server process is
              started, after it conducts the authentication  procedure.   This
              is  intended  to  give  an  opportunity  to attach to the server
              process with a debugger.

   OPTIONS FOR SINGLE-USER MODE
       The following options only apply to the single-user mode.

       --single
              Selects the single-user mode. This must be the first argument on
              the command line.

       database
              Specifies  the name of the database to be accessed. This must be
              the last argument on the command  line.  If  it  is  omitted  it
              defaults to the user name.

       -E     Echo all commands.

       -j     Disables use of newline as a statement delimiter.

       -r filename
              Send  all  server  log  output  to filename. In normal multiuser
              mode, this  option  is  ignored,  and  stderr  is  used  by  all
              processes.

ENVIRONMENT

       PGCLIENTENCODING
              Default  character  encoding  used  by clients. (The clients can
              override this individually.) This value can also be set  in  the
              configuration file.

       PGDATA Default data directory location

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

       PGPORT Default port (preferably set in the configuration file)

       TZ     Server time zone

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 in the documentation. You might  be
       able to postpone reconfiguring your kernel by decreasing shared_buffers
       to reduce the  shared  memory  consumption  of  PostgreSQL,  and/or  by
       reducing max_connections to reduce the semaphore consumption.

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

       $ ps ax | grep postgres

       or

       $ ps -ef | grep postgres

       depending on your system. If you are certain that no conflicting server
       is  running,  you can remove the lock file mentioned in the message and
       try again.

       A failure message indicating inability to bind to a port might indicate
       that  that  port  is already in use by some non-PostgreSQL process. You
       might also get this error if you  terminate  postgres  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 might 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

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

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

       To terminate the postgres server 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,
       resulting in a recovery run during restart.

       The  SIGHUP  signal  will  reload the server configuration files. It is
       also possible to send SIGHUP to an individual server process, but  that
       is usually not sensible.

       To  cancel  a  running  query,  send  the  SIGINT signal to the process
       running that command.

       The postgres server uses SIGTERM to tell subordinate  server  processes
       to  quit  normally and SIGQUIT to terminate without the normal cleanup.
       These signals should not be used by users. It is also  unwise  to  send
       SIGKILL  to a server process — the main postgres process will interpret
       this as a crash and will force all the sibling  processes  to  quit  as
       part of its standard crash-recovery procedure.

BUGS

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

USAGE

       To start a single-user mode server, use a command like

       postgres --single -D /usr/local/pgsql/data other-options my_database

       Provide  the  correct  path  to the database directory with -D, or make
       sure that the environment variable PGDATA is  set.   Also  specify  the
       name of the particular database you want to work in.

       Normally,  the  single-user  mode  server treats newline as the command
       entry terminator; there is no intelligence about semicolons,  as  there
       is  in psql. To continue a command across multiple lines, you must type
       backslash just before each newline except the last one.

       But if you use the -j  command  line  switch,  then  newline  does  not
       terminate  command  entry.  In  this  case,  the  server  will read the
       standard input until the end-of-file (EOF)  marker,  then  process  the
       input  as  a  single  command  string. Backslash-newline is not treated
       specially in this case.

       To quit the session, type EOF (Control+D, usually).  If you’ve used -j,
       two consecutive EOFs are needed to exit.

       Note  that  the  single-user mode server does not provide sophisticated
       line-editing features (no command history, for example).

EXAMPLES

       To start postgres in the background using default values, type:

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

       To start postgres with a specific port:

       $ postgres -p 1234

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

       $ psql -p 1234

       or set the environment variable PGPORT:

       $ export PGPORT=1234
       $ psql

       Named run-time parameters can be set in either of these styles:

       $ postgres -c work_mem=1234
       $ postgres --work-mem=1234

       Either form overrides whatever setting  might  exist  for  work_mem  in
       postgresql.conf.  Notice  that  underscores  in  parameter names can be
       written as either underscore or dash on the command  line.  Except  for
       short-term  experiments,  it’s  probably  better  practice  to edit the
       setting in postgresql.conf than to rely on a command-line switch to set
       a parameter.

SEE ALSO

       initdb(1), pg_ctl(1)