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3.3 pg_ctl

Name

pg_ctl -- initialize, start, stop, or restart a PostgreSQL server

Synopsis

pg_ctl init[db] [-s] [-D datadir] [-o options]

pg_ctl start [-w] [-t seconds] [-s] [-D datadir] [-l
 filename] [-o options] [-p path] [-c]

pg_ctl stop [-W] [-t seconds] [-s] [-D datadir] [-ms[mart] |
 f[ast] | i[mmediate]]

pg_ctl restart [-w] [-t seconds] [-s] [-D datadir] [-c]
 [-ms[mart] | f[ast] | i[mmediate]] [-o options]

pg_ctl reload [-s] [-D datadir]

pg_ctl status [-D datadir]

pg_ctl kill [signal_name] [process_id]

pg_ctl register [-N servicename] [-U username] [-P password]
 [-D datadir] [-w] [-t seconds] [-o options]

pg_ctl unregister [-N servicename]

Description

pg_ctl is a utility for initializing a PostgreSQL database cluster, starting, stopping, or restarting the PostgreSQL backend server ( postgres), 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.

The init or initdb mode creates a new PostgreSQL database cluster. A database cluster is a collection of databases that are managed by a single server instance. This mode invokes the initdb command. See initdb for details.

In start mode, a new server is launched. The server is started in the background, and standard input is attached to ‘/dev/null’ (or nul on Windows). On Unix-like systems, by default, the server's standard output and standard error are send to pg_ctl's standard output (not standard error). The standard output of pg_ctl should then be redirected to a file or piped to another process such as a log rotating program like rotatelogs; otherwise postgres will write its output to the controlling terminal (from the background) and will not leave the shell's process group. On Windows, by default the server's standard output and standard error are sent to the terminal. These default behaviors can be changed by using -l to append server output to a log file.

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 online backup mode to finish and all the clients to disconnect. This is the default. If the server is in recovery, recovery and streaming replication will be terminated once all clients have disconnected. “Fast” mode does not wait for clients to disconnect and will terminate an online backup in progress. 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 postgres command-line options.

reload mode simply sends the postgres 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.

Options

-c

Attempt to allow server crashes to produce core files, on platforms where this available, by lifting any soft resource limit placed on them. This is useful in debugging or diagnosing problems by allowing a stack trace to be obtained from a failed server process.

-D datadir

Specifies the file system location of the database files. If this is omitted, the environment variable PGDATA is used.

-l filename

Append the server log output to filename. If the file does not exist, it is created. The umask is set to 077, so access to the log file from other users is disallowed by default.

-m mode

Specifies the shutdown mode. mode can be smart, fast, or immediate, or the first letter of one of these three.

-o options

Specifies options to be passed directly to the postgres command. The options are usually surrounded by single or double quotes to ensure that they are passed through as a group.

-p path

Specifies the location of the ‘postgres’ executable. By default the ‘postgres’ executable is taken from the same directory as pg_ctl, or failing that, the hard-wired installation directory. It is not necessary to use this option unless you are doing something unusual and get errors that the ‘postgres’ executable was not found. In init mode, this option analogously specifies the location of the ‘initdb’ executable.

-s

Only print errors, no informational messages.

-t

The number of seconds to wait when waiting for start or shutdown to complete.

-w

Wait for the start or shutdown to complete. The default wait time is 60 seconds. This is the default option for shutdowns. A successful shutdown is indicated by removal of the PID file. For starting up, a successful psql -l indicates success. pg_ctl will attempt to use the proper port for psql. If the environment variable PGPORT exists, that is used. Otherwise, it will see if a port has been set in the ‘postgresql.conf’ file. If neither of those is used, it will use the default port that PostgreSQL was compiled with (5432 by default). When waiting, pg_ctl will return an accurate exit code based on the success of the startup or shutdown.

-W

Do not wait for start or shutdown to complete. This is the default for starts and restarts.

Options for Windows

-N servicename

Name of the system service to register. The name will be used as both the service name and the display name.

-P password

Password for the user to start the service.

-U username

User name for the user to start the service. For domain users, use the format DOMAIN\username.

Environment

PGDATA

Default data directory location.

PGHOST

Default host name or Unix-domain socket location for psql (used by the -w option).

PGPORT

Default port number for psql (used by the -w option).

For additional server variables, see postgres. This utility, like most other PostgreSQL utilities, also uses the environment variables supported by libpq (see Volume 2: Environment Variables).

Files

‘postmaster.pid’

The existence of this file in the data directory is used to help pg_ctl determine if the server is currently running or not.

‘postmaster.opts’

If this file exists in the data directory, pg_ctl (in restart mode) will pass the contents of the file as options to postgres, unless overridden by the -o option. The contents of this file are also displayed in status mode.

‘postgresql.conf’

This file, located in the data directory, is parsed to find the proper port to use with psql when the -w is given in start mode.

Notes

Waiting for complete start is not a well-defined operation and might fail if access control is set up so that a local client cannot connect without manual interaction (e.g., password authentication). For additional connection variables, see Volume 2: Environment Variables, and for passwords, also see Volume 2: The Password File.

Examples

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 fsync, use:

$ pg_ctl -o "-F -p 5433" start

Stopping the Server

$ pg_ctl stop

stops the server. Using the -m switch allows one to control how 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: server is running (pid: 13718)
Command line was:
/usr/local/pgsql/bin/postgres '-D' '/usr/local/pgsql/data' 
  '-p' '5433' '-B' '128'

This is the command line that would be invoked in restart mode.

See Also

initdb, postgres