pg_ctl is a utility for starting, stopping, or restarting the PostgreSQL backend server (
), or displaying the status of a running server. Although the server can be started manually, pg_ctl encapsulates tasks such as redirecting log output and properly detaching from the terminal and process group. It also provides convenient options for controlled shutdown.
In start mode, a new server is launched. The server is started in the background, and standard input is attached to /dev/null. The standard output and standard error are either appended to a log file (if the -l option is used), or redirected to pg_ctl's standard output (not standard error). If no log file is chosen, the standard output of pg_ctl should be redirected to a file or piped to another process such as a log rotating program like rotatelogs; otherwise the postmaster will write its output to the controlling terminal (from the background) and will not leave the shell's process group.
In stop mode, the server that is running in the specified data directory is shut down. Three different shutdown methods can be selected with the -m option: "Smart" mode waits for all the clients to disconnect. This is the default. "Fast" mode does not wait for clients to disconnect. All active transactions are rolled back and clients are forcibly disconnected, then the server is shut down. "Immediate" mode will abort all server processes without a clean shutdown. This will lead to a recovery run on restart.
restart mode effectively executes a stop followed by a start. This allows changing the postmaster command-line options.
reload mode simply sends the postmaster process a SIGHUP signal, causing it to reread its configuration files (postgresql.conf, pg_hba.conf, etc.). This allows changing of configuration-file options that do not require a complete restart to take effect.
status mode checks whether a server is running in the specified data directory. If it is, the PID and the command line options that were used to invoke it are displayed.
kill mode allows you to send a signal to a specified process. This is particularly valuable for Microsoft Windows which does not have a kill command. Use --help to see a list of supported signal names.
register mode allows you to register a system service on Microsoft Windows.
unregister mode allows you to unregister a system service on Microsoft Windows, previously registered with the register command.
Starting the Server
To start up a server:
$ pg_ctl start
An example of starting the server, blocking until the server has come up is:
$ pg_ctl -w start
For a server using port 5433, and running without
$ pg_ctl -o "-F -p 5433" start
Stopping the Server
$ pg_ctl stop
stops the server. Using the -m switch allows one to control
the backend shuts down.
Restarting the Server
Restarting the server is almost equivalent to stopping the server and starting it again except that pg_ctl saves and reuses the command line options that were passed to the previously running instance. To restart the server in the simplest form, use:
$ pg_ctl restart
To restart server, waiting for it to shut down and to come up:
$ pg_ctl -w restart
To restart using port 5433 and disabling
fsync after restarting:
$ pg_ctl -o "-F -p 5433" restart
Showing the Server Status
Here is a sample status output from pg_ctl:
$ pg_ctl status
pg_ctl: postmaster is running (pid: 13718)
Command line was:
/usr/local/pgsql/bin/postmaster '-D' '/usr/local/pgsql/data' '-p' '5433' '-B' '128'
This is the command line that would be invoked in restart mode.