postmaster is the PostgreSQL multiuser 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 separate server process
("postgres") to handle the
connection. The postmaster also manages
the communication among server processes.
[root@usha data]# ls -l total 92 drwx------. 5 postgres postgres 4096 Feb 19 13:00 base drwx------. 2 postgres postgres 4096 Feb 19 21:14 global drwx------. 2 postgres postgres 4096 Feb 19 13:00 pg_clog -rw-------. 1 postgres postgres 4232 Feb 19 13:00 pg_hba.conf -rw-------. 1 postgres postgres 1636 Feb 19 13:00 pg_ident.conf drwx------. 2 postgres postgres 4096 Feb 19 13:30 pg_log drwx------. 4 postgres postgres 4096 Feb 19 13:00 pg_multixact drwx------. 2 postgres postgres 4096 Feb 19 13:30 pg_notify drwx------. 2 postgres postgres 4096 Feb 19 13:00 pg_serial drwx------. 2 postgres postgres 4096 Feb 19 21:33 pg_stat_tmp drwx------. 2 postgres postgres 4096 Feb 19 13:00 pg_subtrans drwx------. 2 postgres postgres 4096 Feb 19 13:00 pg_tblspc drwx------. 2 postgres postgres 4096 Feb 19 13:00 pg_twophase -rw-------. 1 postgres postgres 4 Feb 19 13:00 PG_VERSION drwx------. 3 postgres postgres 4096 Feb 19 13:00 pg_xlog -rw-------. 1 postgres postgres 19146 Feb 19 13:00 postgresql.conf -rw-------. 1 postgres postgres 71 Feb 19 13:30 postmaster.opts -rw-------. 1 postgres postgres 81 Feb 19 13:30 postmaster.pid [root@usha data]# cat postmaster.pid 11987 /var/lib/pgsql/9.1/data 1329676222 5432 /tmp localhost 5432001 48234497 [root@usha data]# 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] By default the postmaster starts in the foreground and prints log messages to the standard error stream. 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 cluster. A database cluster is a collection of databases that is stored at a common file system location (the "data area"). More than one postmaster 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 initdb. When the postmaster 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. Options |