PostgreSQL: Documentation: 9.4: postgres

PostgreSQL: Documentation: 9.4: postgres

时间:2015-06-15 09:45来源:网络整理 作者:KKWL 点击:
PostgreSQL 9.4.4 Documentation postgres Namepostgres-- PostgreSQL database server Synopsis postgres [option...] Description postgres is the PostgreSQL database server. In order for a client application to access a database it connects (over

PostgreSQL 9.4.4 Documentation


Namepostgres -- PostgreSQL database server


postgres [option...]


postgres is the PostgreSQL database server. In order for a client application to access a database it connects (over a network or locally) to a running postgres instance. The postgres instance then starts a separate server process to handle the connection.

One postgres instance always manages the data of exactly one database cluster. A database cluster is a collection of databases that is stored at a common file system location (the "data area"). More than one postgres instance can run on a system at one time, so long as they use different data areas and different communication ports (see below). When postgres starts it needs to know the location of the data area. The location must be specified by the -D option or the PGDATA environment variable; there is no default. Typically, -D or PGDATA points directly to the data area directory created by initdb. Other possible file layouts are discussed in Section 18.2.

By default postgres starts in the foreground and prints log messages to the standard error stream. In practical applications postgres should be started as a background process, perhaps at boot time.

The postgres command can also be called in single-user mode. The primary use for this mode is during bootstrapping by initdb. Sometimes it is used for debugging or disaster recovery; note that running a single-user server is not truly suitable for debugging the server, since no realistic interprocess communication and locking will happen. When invoked in single-user mode from the shell, the user can enter queries and the results will be printed to the screen, but in a form that is more useful for developers than end users. In the single-user mode, the session user will be set to the user with ID 1, and implicit superuser powers are granted to this user. This user does not actually have to exist, so the single-user mode can be used to manually recover from certain kinds of accidental damage to the system catalogs.


postgres accepts the following command-line arguments. For a detailed discussion of the options consult Chapter 18. You can save typing most of these options by setting up a configuration file. Some (safe) options can also be set from the connecting client in an application-dependent way to apply only for that session. For example, if the environment variable PGOPTIONS is set, then libpq-based clients will pass that string to the server, which will interpret it as postgres command-line options.

General Purpose

-A 0|1

Enables run-time assertion checks, which is a debugging aid to detect programming mistakes. This option is only available if assertions were enabled when PostgreSQL was compiled. If so, the default is on.

-B nbuffers

Sets the number of shared buffers for use by the server processes. The default value of this parameter is chosen automatically by initdb. Specifying this option is equivalent to setting the configuration parameter.

-c name=value

Sets a named run-time parameter. The configuration parameters supported by PostgreSQL are described in Chapter 18. Most of the other command line options are in fact short forms of such a parameter assignment. -c can appear multiple times to set multiple parameters.

-C name

Prints the value of the named run-time parameter, and exits. (See the -c option above for details.) This can be used on a running server, and returns values from postgresql.conf, modified by any parameters supplied in this invocation. It does not reflect parameters supplied when the cluster was started.

This option is meant for other programs that interact with a server instance, such as pg_ctl, to query configuration parameter values. User-facing applications should instead use SHOW or the pg_settings view.

-d debug-level

Sets the debug level. The higher this value is set, the more debugging output is written to the server log. Values are from 1 to 5. It is also possible to pass -d 0 for a specific session, which will prevent the server log level of the parent postgres process from being propagated to this session.

-D datadir

Specifies the file system location of the database configuration files. See Section 18.2 for details.


Sets the default date style to "European", that is DMY ordering of input date fields. This also causes the day to be printed before the month in certain date output formats. See Section 8.5 for more information.


Disables fsync calls for improved performance, at the risk of data corruption in the event of a system crash. Specifying this option is equivalent to disabling the configuration parameter. Read the detailed documentation before using this!

-h hostname