There are several ways to shut down the database server. You control
the type of shutdown by sending different signals to the
edb-postmaster process.
- SIGTERM
After receiving SIGTERM, the server
disallows new connections, but lets existing sessions end their
work normally. It shuts down only after all of the sessions
terminate normally. This is the Smart
Shutdown.
- SIGINT
The server disallows new connections and sends all existing
server processes SIGTERM, which will cause them
to abort their current transactions and exit promptly. It then
waits for the server processes to exit and finally shuts down. This is the
Fast Shutdown.
- SIGQUIT
This is the Immediate Shutdown, which
will cause the edb-postmaster process to send a
SIGQUIT to all child processes and exit
immediately (without properly shutting itself down). The child processes
likewise exit immediately upon receiving
SIGQUIT. This will lead to recovery (by
replaying the WAL log) upon next start-up. This is recommended
only in emergencies.
Important: It is best not to use SIGKILL to shut down
the server. This will prevent the server from releasing
shared memory and semaphores, which may then have to be done by
manually.
The PID of the edb-postmaster process can be found using the
ps program, or from the file
edb-postmaster.pid in the data directory. So for
example, to do a fast shutdown:
$ kill -INT `head -1 /usr/local/pgsql/data/edb-postmaster.pid`
The program pg_ctl is a shell script
that provides a more convenient interface for shutting down the
server.
