POSTGRESQL(UNIX)
NAME
postgres - the Postgres backend server
SYNOPSIS
postgres [-B n_buffers] [-D data_directory] [-E ] [-F ]
[-P filedes] [-Q ] [-S n_buffers ] [-e ] [-v protocol ]
[-d debug_level] [-o output_file] [-s ] [dbname]
DESCRIPTION
The Postgres backend server can be executed directly from
the user shell. This should be done only while debugging
by the DBA, and should not be done while other Postgres
backends are being managed by a postmaster on this set of
databases.
The optional argument dbname specifies the name of the
database to be accessed. Dbname defaults to the value of
the USER environment variable.
The postgres server understands the following command-line
options:
-D data_directory
This option specifies the pathname of the directory
that contains the database system data (the tables,
the catalogs, etc.). If you don't specify this
option, Postgres uses the value of the PGDATA envi-
ronment variable. You must either specify a -D
option or set PGDATA.
The data directory pathname for a database system is
normally determined when the database system is cre-
ated with initdb, with a --pgdata option to initdb.
-B n_buffers
If the backend is running under the postmaster,
n_buffers is the number of shared-memory buffers that
the postmaster has allocated for the backend server
processes that it starts. If the backend is running
standalone, this specifies the number of buffers to
allocate. This value defaults to 64, and each buffer
is 8k bytes.
-E Echo all queries.
-F Disable automatic fsync() call after each transac-
tion. This option improves performance, but an oper-
ating system crash while a transaction is in progress
will probably cause data loss.
-P filedes
filedes specifies the file descriptor that corre-
sponds to the socket (port) on which to communicate
to the frontend process. This option is not useful
for interactive use.
-Q Specifies "quiet" mode.
-S Specifies the amount of memory to be used by internal
sorts before using disk files for sorting. This
value is specified in 1k bytes, and defaults to 512.
-e The -e option controls how dates are input to and
output from the database.
If the -e option is supplied, then all dates passed
to and from the frontend processes will be assumed to
be in European format ie. DD-MM-YYYY otherwise dates
are input and output in American format ie. MM-DD-
YYYY
-d debug_level
Turns on debugging at the numeric level debug_level.
Turning on debugging will cause query, parse trees,
and query plans to be displayed.
-o output_file
Sends all debugging and error output to output_file.
If the backend is running under the postmaster, error
messages are still sent to the frontend process as
well as to output_file, but debugging output is sent
to the controlling tty of the postmaster (since only
one file descriptor can be sent to an actual file).
-s Print time information and other statistics at the
end of each query. This is useful for benchmarking
or for use in tuning the number of buffers.
-v protocol
Specifies the number of the frontend/backend protocol
to be used for this particular session.
DEPRECATED COMMAND OPTIONS
There are several other options that may be specified,
used mainly for debugging purposes. These are listed here
only for the use by Postgres system developers. Use of
any of these options is highly discouraged. Furthermore,
any of these options may disappear or change at any time.
-An|r|b|Qn|Xn
This option generates a tremendous amount of out-
put.
-L Turns off the locking system.
-N Disables use of newline as a query delimiter.
-b Enables generation of bushy query plan trees (as
opposed to left-deep query plans trees). These
query plans are not intended for actual execution;
in addition, this flag often causes Postgres to run
out of memory.
-f Forbids the use of particular scan and join meth-
ods: s and i disable sequential and index scans
respectively, while n, m and h disable nested-loop,
merge and hash joins respectively. This is another
feature that may not necessarily produce executable
plans.
-p Indicates to the backend server that it has been
started by a postmaster and make different assump-
tions about buffer pool management, file descrip-
tors, etc.
-tpa[rser]|pl[anner]|e[xecutor]
Print timing statistics for each query relating to
each of the major system modules. This option can-
not be used with -s.
SEE ALSO
ipcclean(1) psql(1) postmaster(1).
DIAGNOSTICS
Of the nigh-infinite number of error messages you may see
when you execute the backend server directly, the most
common will probably be:
semget: No space left on device
If you see this message, you should run the ipc-
clean command. After doing this, try starting
postgres again. If this still doesn't work, you
probably need to configure your kernel for shared
memory and semaphores as described in the installa-
tion notes.