postgres

## Name

postgres — run a PostgreSQL server in single-user mode

## Synopsis

`postgres` [-A [0] | [1] ] [-B `nbuffers`] [-c `name`=`value`] [-d `debug-level`] [--describe-config] [-D `datadir`] [-e] [-E] [-f [s] | [i] | [t] | [n] | [m] | [h] ] [-F] [-N] [-o `filename`] [-O] [-P] [[-s] | [-t [pa] | [pl] | [ex] ]] [-S `work-mem`] [-W `seconds`] [--`name`=`value`] `database`
`postgres` [-A [0] | [1] ] [-B `nbuffers`] [-c `name`=`value`] [-d `debug-level`] [-D `datadir`] [-e] [-f [s] | [i] | [t] | [n] | [m] | [h] ] [-F] [-o `filename`] [-O] [-p `database`] [-P] [[-s] | [-t [pa] | [pl] | [ex] ]] [-S `work-mem`] [-v `protocol`] [-W `seconds`] [--`name`=`value`]

## Description

The `postgres` executable is the actual PostgreSQL server process that processes queries. It is normally not called directly; instead a postmaster multiuser server is started.

The second form above is how `postgres` is invoked by the postmaster (only conceptually, since both `postmaster` and `postgres` are in fact the same program); it should not be invoked directly this way. The first form invokes the server directly in interactive single-user mode. The primary use for this mode is during bootstrapping by initdb. Sometimes it is used for debugging or disaster recovery.

When invoked in interactive 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. But 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 running a stand-alone server, the session user will be set to the user with ID 1. This user does not actually have to exist, so a stand-alone server can be used to manually recover from certain kinds of accidental damage to the system catalogs. Implicit superuser powers are granted to the user with ID 1 in stand-alone mode.

## Options

When `postgres` is started by a postmaster then it inherits all options set by the latter. Additionally, `postgres`-specific options can be passed from the `postmaster` with the `-o` switch.

You can avoid having to type these options by setting up a configuration file. See Chapter 17, Server Configuration for details. Some (safe) options can also be set from the connecting client in an application-dependent way. 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

The options `-A`, `-B`, `-c`, `-d`, `-D`, `-F`, and `--`name`` have the same meanings as the postmaster except that `-d 0` prevents the server log level of the `postmaster` from being propagated to `postgres`.

`-e`

  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, “Date/Time Types” for more information.

`-o` `filename`

  Send all server log output to `filename`. If `postgres` is running under the `postmaster`, this option is ignored, and the stderr inherited from the `postmaster` is used.

`-P`

  Ignore system indexes when reading system tables (but still update the indexes when modifying the tables). This is useful when recovering from damaged system indexes.

`-s`

  Print time information and other statistics at the end of each command. This is useful for benchmarking or for use in tuning the number of buffers.

`-S` `work-mem`

  Specifies the amount of memory to be used by internal sorts and hashes before resorting to temporary disk files. See the description of the `work_mem` configuration parameter in Section 17.4.1, “Memory”.

### Options for stand-alone mode

`database`

  Specifies the name of the database to be accessed. If it is omitted it defaults to the user name.

`-E`

  Echo all commands.

`-N`

  Disables use of newline as a statement delimiter.

### Semi-internal Options

There are several other options that may be specified, used mainly for debugging purposes. These are listed here only for the use by PostgreSQL system developers. Use of any of these options is highly discouraged. Furthermore, any of these options may disappear or change in a future release without notice.

`-f` `{ s | i | m | n | h }`

  Forbids the use of particular scan and join methods: `s` and `i` disable sequential and index scans respectively, while `n`, `m`, and `h` disable nested-loop, merge and hash joins respectively.

  ### Note

  Neither sequential scans nor nested-loop joins can be disabled completely; the `-fs` and `-fn` options simply discourage the optimizer from using those plan types if it has any other alternative.

`-O`

  Allows the structure of system tables to be modified. This is used by `initdb`.

`-p` `database`

  Indicates that this process has been started by a `postmaster` and specifies the database to use. etc.

`-t` `pa[rser] | pl[anner] | e[xecutor]`

  Print timing statistics for each query relating to each of the major system modules. This option cannot be used together with the `-s` option.

`-v` `protocol`

  Specifies the version number of the frontend/backend protocol to be used for this particular session.

`-W` `seconds`

  As soon as this option is encountered, the process sleeps for the specified amount of seconds. This gives developers time to attach a debugger to the server process.

`--describe-config`

  This option dumps out the server's internal configuration variables, descriptions, and defaults in tab-delimited `COPY` format. It is designed primarily for use by administration tools.

## Environment

`PGDATA`

  Default data directory location

For others, which have little influence during single-user mode, see postmaster.

## Notes

To cancel a running query, send the `SIGINT` signal to the `postgres` process running that command.

To tell `postgres` to reload the configuration files, send a `SIGHUP` signal. Normally it's best to `SIGHUP` the `postmaster` instead; the `postmaster` will in turn `SIGHUP` each of its children. But in some cases it might be desirable to have only one `postgres` process reload the configuration files.

The `postmaster` uses `SIGTERM` to tell a `postgres` process to quit normally and `SIGQUIT` to terminate without the normal cleanup. These signals should not be used by users. It is also unwise to send `SIGKILL` to a `postgres` process [mdash ] the `postmaster` will interpret this as a crash in `postgres`, and will force all the sibling `postgres` processes to quit as part of its standard crash-recovery procedure.

## Usage

Start a stand-alone server with a command like

    postgres -D /usr/local/pgsql/data other-options my_database

Provide the correct path to the database directory with `-D`, or make sure that the environment variable `PGDATA` is set. Also specify the name of the particular database you want to work in.

Normally, the stand-alone server treats newline as the command entry terminator; there is no intelligence about semicolons, as there is in psql. To continue a command across multiple lines, you must type backslash just before each newline except the last one.

But if you use the `-N` command line switch, then newline does not terminate command entry. In this case, the server will read the standard input until the end-of-file (EOF) marker, then process the input as a single command string. Backslash-newline is not treated specially in this case.

To quit the session, type EOF (Control+D, usually). If you've used `-N`, two consecutive EOFs are needed to exit.

Note that the stand-alone server does not provide sophisticated line-editing features (no command history, for example).

## See Also

initdb, ipcclean, postmaster