1POSTGRES(1) PostgreSQL 12.6 Documentation POSTGRES(1)
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6 postgres - PostgreSQL database server
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9 postgres [option...]
10
12 postgres is the PostgreSQL database server. In order for a client
13 application to access a database it connects (over a network or
14 locally) to a running postgres instance. The postgres instance then
15 starts a separate server process to handle the connection.
16 One postgres instance always manages the data of exactly one database
18 cluster. A database cluster is a collection of databases that is stored
19 at a common file system location (the “data area”). More than one
20 postgres instance can run on a system at one time, so long as they use
21 different data areas and different communication ports (see below).
22 When postgres starts it needs to know the location of the data area.
23 The location must be specified by the -D option or the PGDATA
24 environment variable; there is no default. Typically, -D or PGDATA
25 points directly to the data area directory created by initdb(1). Other
26 possible file layouts are discussed in Section 19.2.
27 By default postgres starts in the foreground and prints log messages to
29 the standard error stream. In practical applications postgres should be
30 started as a background process, perhaps at boot time.
31 The postgres command can also be called in single-user mode. The
33 primary use for this mode is during bootstrapping by initdb(1).
34 Sometimes it is used for debugging or disaster recovery; note that
35 running a single-user server is not truly suitable for debugging the
36 server, since no realistic interprocess communication and locking will
37 happen. When invoked in single-user mode from the shell, the user can
38 enter queries and the results will be printed to the screen, but in a
39 form that is more useful for developers than end users. In the
40 single-user mode, the session user will be set to the user with ID 1,
41 and implicit superuser powers are granted to this user. This user does
42 not actually have to exist, so the single-user mode can be used to
43 manually recover from certain kinds of accidental damage to the system
44 catalogs.
45
47 postgres accepts the following command-line arguments. For a detailed
48 discussion of the options consult Chapter 19. You can save typing most
49 of these options by setting up a configuration file. Some (safe)
50 options can also be set from the connecting client in an
51 application-dependent way to apply only for that session. For example,
52 if the environment variable PGOPTIONS is set, then libpq-based clients
53 will pass that string to the server, which will interpret it as
54 postgres command-line options.
55 General Purpose
57 -B nbuffers
58 Sets the number of shared buffers for use by the server processes.
59 The default value of this parameter is chosen automatically by
60 initdb. Specifying this option is equivalent to setting the
61 shared_buffers configuration parameter.
62 -c name=value
64 Sets a named run-time parameter. The configuration parameters
65 supported by PostgreSQL are described in Chapter 19. Most of the
66 other command line options are in fact short forms of such a
67 parameter assignment. -c can appear multiple times to set multiple
68 parameters.
69 -C name
71 Prints the value of the named run-time parameter, and exits. (See
72 the -c option above for details.) This can be used on a running
73 server, and returns values from postgresql.conf, modified by any
74 parameters supplied in this invocation. It does not reflect
75 parameters supplied when the cluster was started.
76 This option is meant for other programs that interact with a server
78 instance, such as pg_ctl(1), to query configuration parameter
79 values. User-facing applications should instead use SHOW(7) or the
80 pg_settings view.
81 -d debug-level
83 Sets the debug level. The higher this value is set, the more
84 debugging output is written to the server log. Values are from 1 to
85 5. It is also possible to pass -d 0 for a specific session, which
86 will prevent the server log level of the parent postgres process
87 from being propagated to this session.
88 -D datadir
90 Specifies the file system location of the database configuration
91 files. See Section 19.2 for details.
92 -e
94 Sets the default date style to “European”, that is DMY ordering of
95 input date fields. This also causes the day to be printed before
96 the month in certain date output formats. See Section 8.5 for more
97 information.
98 -F
100 Disables fsync calls for improved performance, at the risk of data
101 corruption in the event of a system crash. Specifying this option
102 is equivalent to disabling the fsync configuration parameter. Read
103 the detailed documentation before using this!
104 -h hostname
106 Specifies the IP host name or address on which postgres is to
107 listen for TCP/IP connections from client applications. The value
108 can also be a comma-separated list of addresses, or * to specify
109 listening on all available interfaces. An empty value specifies not
110 listening on any IP addresses, in which case only Unix-domain
111 sockets can be used to connect to the server. Defaults to listening
112 only on localhost. Specifying this option is equivalent to setting
113 the listen_addresses configuration parameter.
114 -i
116 Allows remote clients to connect via TCP/IP (Internet domain)
117 connections. Without this option, only local connections are
118 accepted. This option is equivalent to setting listen_addresses to
119 * in postgresql.conf or via -h.
120 This option is deprecated since it does not allow access to the
122 full functionality of listen_addresses. It's usually better to set
123 listen_addresses directly.
124 -k directory
126 Specifies the directory of the Unix-domain socket on which postgres
127 is to listen for connections from client applications. The value
128 can also be a comma-separated list of directories. An empty value
129 specifies not listening on any Unix-domain sockets, in which case
130 only TCP/IP sockets can be used to connect to the server. The
131 default value is normally /tmp, but that can be changed at build
132 time. Specifying this option is equivalent to setting the
133 unix_socket_directories configuration parameter.
134 -l
136 Enables secure connections using SSL. PostgreSQL must have been
137 compiled with support for SSL for this option to be available. For
138 more information on using SSL, refer to Section 18.9.
139 -N max-connections
141 Sets the maximum number of client connections that this server will
142 accept. The default value of this parameter is chosen automatically
143 by initdb. Specifying this option is equivalent to setting the
144 max_connections configuration parameter.
145 -o extra-options
147 The command-line-style arguments specified in extra-options are
148 passed to all server processes started by this postgres process.
149 Spaces within extra-options are considered to separate arguments,
151 unless escaped with a backslash (\); write \\ to represent a
152 literal backslash. Multiple arguments can also be specified via
153 multiple uses of -o.
154 The use of this option is obsolete; all command-line options for
156 server processes can be specified directly on the postgres command
157 line.
158 -p port
160 Specifies the TCP/IP port or local Unix domain socket file
161 extension on which postgres is to listen for connections from
162 client applications. Defaults to the value of the PGPORT
163 environment variable, or if PGPORT is not set, then defaults to the
164 value established during compilation (normally 5432). If you
165 specify a port other than the default port, then all client
166 applications must specify the same port using either command-line
167 options or PGPORT.
168 -s
170 Print time information and other statistics at the end of each
171 command. This is useful for benchmarking or for use in tuning the
172 number of buffers.
173 -S work-mem
175 Specifies the amount of memory to be used by internal sorts and
176 hashes before resorting to temporary disk files. See the
177 description of the work_mem configuration parameter in
178 Section 19.4.1.
179 -V
181 --version
182 Print the postgres version and exit.
183 --name=value
185 Sets a named run-time parameter; a shorter form of -c.
186 --describe-config
188 This option dumps out the server's internal configuration
189 variables, descriptions, and defaults in tab-delimited COPY format.
190 It is designed primarily for use by administration tools.
191 -?
193 --help
194 Show help about postgres command line arguments, and exit.
195 Semi-Internal Options
197 The options described here are used mainly for debugging purposes, and
198 in some cases to assist with recovery of severely damaged databases.
199 There should be no reason to use them in a production database setup.
200 They are listed here only for use by PostgreSQL system developers.
201 Furthermore, these options might change or be removed in a future
202 release without notice.
203 -f { s | i | o | b | t | n | m | h }
205 Forbids the use of particular scan and join methods: s and i
206 disable sequential and index scans respectively, o, b and t disable
207 index-only scans, bitmap index scans, and TID scans respectively,
208 while n, m, and h disable nested-loop, merge and hash joins
209 respectively.
210 Neither sequential scans nor nested-loop joins can be disabled
212 completely; the -fs and -fn options simply discourage the optimizer
213 from using those plan types if it has any other alternative.
214 -n
216 This option is for debugging problems that cause a server process
217 to die abnormally. The ordinary strategy in this situation is to
218 notify all other server processes that they must terminate and then
219 reinitialize the shared memory and semaphores. This is because an
220 errant server process could have corrupted some shared state before
221 terminating. This option specifies that postgres will not
222 reinitialize shared data structures. A knowledgeable system
223 programmer can then use a debugger to examine shared memory and
224 semaphore state.
225 -O
227 Allows the structure of system tables to be modified. This is used
228 by initdb.
229 -P
231 Ignore system indexes when reading system tables, but still update
232 the indexes when modifying the tables. This is useful when
233 recovering from damaged system indexes.
234 -t pa[rser] | pl[anner] | e[xecutor]
236 Print timing statistics for each query relating to each of the
237 major system modules. This option cannot be used together with the
238 -s option.
239 -T
241 This option is for debugging problems that cause a server process
242 to die abnormally. The ordinary strategy in this situation is to
243 notify all other server processes that they must terminate and then
244 reinitialize the shared memory and semaphores. This is because an
245 errant server process could have corrupted some shared state before
246 terminating. This option specifies that postgres will stop all
247 other server processes by sending the signal SIGSTOP, but will not
248 cause them to terminate. This permits system programmers to collect
249 core dumps from all server processes by hand.
250 -v protocol
252 Specifies the version number of the frontend/backend protocol to be
253 used for a particular session. This option is for internal use
254 only.
255 -W seconds
257 A delay of this many seconds occurs when a new server process is
258 started, after it conducts the authentication procedure. This is
259 intended to give an opportunity to attach to the server process
260 with a debugger.
261 Options for Single-User Mode
263 The following options only apply to the single-user mode (see
264 SINGLE-USER MODE).
265 --single
267 Selects the single-user mode. This must be the first argument on
268 the command line.
269 database
271 Specifies the name of the database to be accessed. This must be the
272 last argument on the command line. If it is omitted it defaults to
273 the user name.
274 -E
276 Echo all commands to standard output before executing them.
277 -j
279 Use semicolon followed by two newlines, rather than just newline,
280 as the command entry terminator.
281 -r filename
283 Send all server log output to filename. This option is only honored
284 when supplied as a command-line option.
285
287 PGCLIENTENCODING
288 Default character encoding used by clients. (The clients can
289 override this individually.) This value can also be set in the
290 configuration file.
291 PGDATA
293 Default data directory location
294 PGDATESTYLE
296 Default value of the DateStyle run-time parameter. (The use of this
297 environment variable is deprecated.)
298 PGPORT
300 Default port number (preferably set in the configuration file)
301
303 A failure message mentioning semget or shmget probably indicates you
304 need to configure your kernel to provide adequate shared memory and
305 semaphores. For more discussion see Section 18.4. You might be able to
306 postpone reconfiguring your kernel by decreasing shared_buffers to
307 reduce the shared memory consumption of PostgreSQL, and/or by reducing
308 max_connections to reduce the semaphore consumption.
309 A failure message suggesting that another server is already running
311 should be checked carefully, for example by using the command
312 $ ps ax | grep postgres
314 or
316 $ ps -ef | grep postgres
318 depending on your system. If you are certain that no conflicting server
320 is running, you can remove the lock file mentioned in the message and
321 try again.
322 A failure message indicating inability to bind to a port might indicate
324 that that port is already in use by some non-PostgreSQL process. You
325 might also get this error if you terminate postgres and immediately
326 restart it using the same port; in this case, you must simply wait a
327 few seconds until the operating system closes the port before trying
328 again. Finally, you might get this error if you specify a port number
329 that your operating system considers to be reserved. For example, many
330 versions of Unix consider port numbers under 1024 to be “trusted” and
331 only permit the Unix superuser to access them.
332
334 The utility command pg_ctl(1) can be used to start and shut down the
335 postgres server safely and comfortably.
336 If at all possible, do not use SIGKILL to kill the main postgres
338 server. Doing so will prevent postgres from freeing the system
339 resources (e.g., shared memory and semaphores) that it holds before
340 terminating. This might cause problems for starting a fresh postgres
341 run.
342 To terminate the postgres server normally, the signals SIGTERM, SIGINT,
344 or SIGQUIT can be used. The first will wait for all clients to
345 terminate before quitting, the second will forcefully disconnect all
346 clients, and the third will quit immediately without proper shutdown,
347 resulting in a recovery run during restart.
348 The SIGHUP signal will reload the server configuration files. It is
350 also possible to send SIGHUP to an individual server process, but that
351 is usually not sensible.
352 To cancel a running query, send the SIGINT signal to the process
354 running that command. To terminate a backend process cleanly, send
355 SIGTERM to that process. See also pg_cancel_backend and
356 pg_terminate_backend in Section 9.26.2 for the SQL-callable equivalents
357 of these two actions.
358 The postgres server uses SIGQUIT to tell subordinate server processes
360 to terminate without normal cleanup. This signal should not be used by
361 users. It is also unwise to send SIGKILL to a server process — the main
362 postgres process will interpret this as a crash and will force all the
363 sibling processes to quit as part of its standard crash-recovery
364 procedure.
365
367 The -- options will not work on FreeBSD or OpenBSD. Use -c instead.
368 This is a bug in the affected operating systems; a future release of
369 PostgreSQL will provide a workaround if this is not fixed.
370
372 To start a single-user mode server, use a command like
373 postgres --single -D /usr/local/pgsql/data other-options my_database
375 Provide the correct path to the database directory with -D, or make
377 sure that the environment variable PGDATA is set. Also specify the name
378 of the particular database you want to work in.
379 Normally, the single-user mode server treats newline as the command
381 entry terminator; there is no intelligence about semicolons, as there
382 is in psql. To continue a command across multiple lines, you must type
383 backslash just before each newline except the last one. The backslash
384 and adjacent newline are both dropped from the input command. Note that
385 this will happen even when within a string literal or comment.
386 But if you use the -j command line switch, a single newline does not
388 terminate command entry; instead, the sequence
389 semicolon-newline-newline does. That is, type a semicolon immediately
390 followed by a completely empty line. Backslash-newline is not treated
391 specially in this mode. Again, there is no intelligence about such a
392 sequence appearing within a string literal or comment.
393 In either input mode, if you type a semicolon that is not just before
395 or part of a command entry terminator, it is considered a command
396 separator. When you do type a command entry terminator, the multiple
397 statements you've entered will be executed as a single transaction.
398 To quit the session, type EOF (Control+D, usually). If you've entered
400 any text since the last command entry terminator, then EOF will be
401 taken as a command entry terminator, and another EOF will be needed to
402 exit.
403 Note that the single-user mode server does not provide sophisticated
405 line-editing features (no command history, for example). Single-user
406 mode also does not do any background processing, such as automatic
407 checkpoints or replication.
408
410 To start postgres in the background using default values, type:
411 $ nohup postgres >logfile 2>&1 </dev/null &
413 To start postgres with a specific port, e.g., 1234:
415 $ postgres -p 1234
417 To connect to this server using psql, specify this port with the -p
419 option:
420 $ psql -p 1234
422 or set the environment variable PGPORT:
424 $ export PGPORT=1234
426 $ psql
427 Named run-time parameters can be set in either of these styles:
429 $ postgres -c work_mem=1234
431 $ postgres --work-mem=1234
432 Either form overrides whatever setting might exist for work_mem in
434 postgresql.conf. Notice that underscores in parameter names can be
435 written as either underscore or dash on the command line. Except for
436 short-term experiments, it's probably better practice to edit the
437 setting in postgresql.conf than to rely on a command-line switch to set
438 a parameter.
439
441 initdb(1), pg_ctl(1)
442PostgreSQL 12.6 2021 POSTGRES(1)