PostgreSQL 7.4 Documentation
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# pg_ctl

## Name

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

## Synopsis

`pg_ctl` start [-w] [-s] [-D datadir] [-l filename] [-o options] [-p path]
`pg_ctl` stop [-W] [-s] [-D datadir] [-m s[mart] | f[ast] | i[mmediate] ]
`pg_ctl` restart [-w] [-s] [-D datadir] [-m s[mart] | f[ast] | i[mmediate] ] [-o options]
`pg_ctl` reload [-s] [-D datadir]
`pg_ctl` status [-D datadir]

## Description

pg_ctl is a utility for starting, stopping, or restarting the PostgreSQL backend server (postmaster), 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, for example a log rotating program, otherwise `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.

## Options

-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 may be smart, fast, or immediate, or the first letter of one of these three.

-o options

  Specifies options to be passed directly to the `postmaster` 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 `postmaster` executable. By default the `postmaster` 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 `postmaster` executable was not found.

-s

  Only print errors, no informational messages.

-w

  Wait for the start or shutdown to complete. Times out after 60 seconds. This is the default 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).

-W

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

## Environment

`PGDATA`

  Default data directory location.

`PGPORT`

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

For others, see postmaster.

## 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.default`

  If this file exists in the data directory, pg_ctl (in start mode) will pass the contents of the file as options to the `postmaster` command, unless overridden by the -o option.

`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 the postmaster, 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 may fail if access control is set up so that a local client cannot connect without manual interaction (e.g., password authentication).

## 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: 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.

## See Also

postmaster

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