postgres - run a PostgreSQL server in single-user mode
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 ]
The postgres executable is the actual PostgreSQL server process that processes queries. It is normally not called directly; instead a postmaster(1) multiuser server is started.
The second form above is how postgres is invoked by the postmaster(1) (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(1). 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.
When postgres is started by a postmaster(1) 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 the documentation 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.
The options -A, -B, -c, -d, -D, -F, and --name have the same meanings as the postmaster(1) except that -d 0 prevents the server log level of the postmaster from being propagated to postgres.
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.
For others, which have little influence during single-user mode, see postmaster(1).
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 --- 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.
Start a stand-alone server with a command like
postgres -D /usr/local/pgsql/data other-options my_databaseProvide 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.