Server Start-up and Shutdown

The POSTGRESQL server uses two distinct programs: postmaster and postgres. The postmaster process accepts all requests for database access. It does authentication and starts a postgres process to handle the connection. The postgres process executes user queries and returns results. Figure  illustrates this relationship.

POSTGRESQL sites normally have many postgres processes, but only one postmaster process. One postgres process exists for every open database session.

Once administrators start the postmaster, the postmaster will start postgres backends as connection requests arrive. The postmaster can be started from either the command line or a script. The operating system start-up scripts can even be modified to start the postmaster automatically.

A third way to start the postmaster is using pg_ctl . This utility allows easy starting and stopping of the postmaster. See the pg_ctl manual page for more information.

To stop the postmaster, you can send the process a signal using kill , or use pg_ctl .