postgres -- run a PostgreSQL server in single-user mode
Synopsis
postgres [-A 0 | 1 ] [-B nbuffers] [-c name=value] [-d debug-level] [-D datadir] [-e] [-E] [-f s | i | t | n | m | h ] [-F] [-i] [-N] [-o filename] [-O] [-P] [-s | -t pa | pl | ex ] [-S sort-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] [-i] [-o filename] [-O] [-p database] [-P] [-s | -t pa | pl | ex ] [-S sort-mem] [-v protocol-version] [-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 backend is not truly suitable for
debugging the server since no realistic interprocess communication
and locking will happen.
When running a stand-alone backend, the session user will be set to
the user with ID 1. This user does not actually have to exist, so
a stand-alone backend 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 the Administrator's
Guide 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
-d0 prevents the debugging level of
the postmaster from being propagated to the backend.
-e
Sets the default date style to "European", which
means that the "day before month" (rather than
month before day) rule is used to interpret ambiguous date
input, and that the day is printed before the month in certain
date output formats. See the PostgreSQL User's
Guide for more information.
-ofilename
Sends all debugging and error output to
filename.
If the backend is running under the
postmaster, this option is ignored,
and the stderr inherited from the
postmaster is used.
-P
Ignore system indexes while scanning/updating system tuples. The
REINDEX command for system tables/indexes
requires this option to be used.
-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.
-Ssort-mem
Specifies the amount of memory to be used by internal sorts and hashes
before resorting to temporary disk files. The value is specified in
kilobytes, and defaults to 512 kilobytes. Note that for a complex query,
several sorts and/or hashes might be running in parallel, and each one
will be allowed to use as much as
sort-mem kilobytes
before it starts to put data into temporary files.
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 queries.
-N
Disables use of newline as a query 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.
-i
Prevents query execution, but shows the plan tree.
-O
Allows the structure of system tables to be modified. This is
used by initdb.
-pdatabase
Indicates that this server has been started by a
postmaster and makes different
assumptions about buffer pool management, file descriptors,
etc.
-tpa[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.
-vprotocol
Specifies the version number of the frontend/backend protocol
to be used for this particular session.
-Wseconds
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 backend process.
Environment
PGDATA
Default data direction location
For others, which have little influence during single-user mode,
see postmaster.
Notes
To stop a running query use the SIGINT signal. To
tell postgres to reread the config file,
use a SIGHUP signal. The
postmaster uses SIGTERM
to tell a postgres process to quit normally and
SIGQUIT to terminate without the normal cleanup.
These should not be used by users.
Usage
Start a stand-alone backend with a command like
postgres -D $PGDATA other-options my_database
Provide the correct path to the database area 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 backend 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. The backend will read the standard input
until the end-of-file (EOF) marker, then
process the input as a single query 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 backend does not provide sophisticated
line-editing features (no command history, for example).
