1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>postgres</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="pgwaldump.html" title="pg_waldump" /><link rel="next" href="app-postmaster.html" title="postmaster" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span xmlns="http://www.w3.org/1999/xhtml" class="application">postgres</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgwaldump.html" title="pg_waldump">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><th width="60%" align="center">PostgreSQL Server Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="app-postmaster.html" title="postmaster">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="APP-POSTGRES"><div class="titlepage"></div><a id="id-1.9.5.14.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">postgres</span></span></h2><p>postgres — <span class="productname">PostgreSQL</span> database server</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.5.14.4.1"><code class="command">postgres</code> [<em class="replaceable"><code>option</code></em>...]</p></div></div><div class="refsect1" id="id-1.9.5.14.5"><h2>Description</h2><p>
<code class="command">postgres</code> is the
<span class="productname">PostgreSQL</span> database server. In order
for a client application to access a database it connects (over a
network or locally) to a running <code class="command">postgres</code> instance.
The <code class="command">postgres</code> instance then starts a separate server
process to handle the connection.
</p><p>
One <code class="command">postgres</code> instance always manages the data of
exactly one database cluster. A database cluster is a collection
of databases that is stored at a common file system location (the
<span class="quote">“<span class="quote">data area</span>”</span>). More than one
<code class="command">postgres</code> instance can run on a system at one
time, so long as they use different data areas and different
communication ports (see below). When
<code class="command">postgres</code> starts it needs to know the location
of the data area. The location must be specified by the
<code class="option">-D</code> option or the <code class="envar">PGDATA</code> environment
variable; there is no default. Typically, <code class="option">-D</code> or
<code class="envar">PGDATA</code> points directly to the data area directory
created by <a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle">initdb</span></a>. Other possible file layouts are
discussed in <a class="xref" href="runtime-config-file-locations.html" title="19.2. File Locations">Section 19.2</a>.
</p><p>
By default <code class="command">postgres</code> starts in the
foreground and prints log messages to the standard error stream. In
practical applications <code class="command">postgres</code>
should be started as a background process, perhaps at boot time.
</p><p>
The <code class="command">postgres</code> command can also be called in
single-user mode. The primary use for this mode is during
bootstrapping by <a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle">initdb</span></a>. Sometimes it is used
for debugging or disaster recovery; 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 invoked in single-user
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. In the single-user mode,
the session user will be set to the user with ID 1, and implicit
superuser powers are granted to this user.
This user does not actually have to exist, so the single-user mode
can be used to manually recover from certain
kinds of accidental damage to the system catalogs.
</p></div><div class="refsect1" id="APP-POSTGRES-OPTIONS"><h2>Options</h2><p>
<code class="command">postgres</code> accepts the following command-line
arguments. For a detailed discussion of the options consult <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a>. You can save typing most of these
options by setting up a configuration file. Some (safe) options
can also be set from the connecting client in an
application-dependent way to apply only for that session. For
example, if the environment variable <code class="envar">PGOPTIONS</code> is
set, then <span class="application">libpq</span>-based clients will pass that
string to the server, which will interpret it as
<code class="command">postgres</code> command-line options.
</p><div class="refsect2" id="id-1.9.5.14.6.3"><h3>General Purpose</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-B <em class="replaceable"><code>nbuffers</code></em></code></span></dt><dd><p>
Sets the number of shared buffers for use by the server
processes. The default value of this parameter is chosen
automatically by <span class="application">initdb</span>.
Specifying this option is equivalent to setting the
<a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a> configuration parameter.
</p></dd><dt><span class="term"><code class="option">-c <em class="replaceable"><code>name</code></em>=<em class="replaceable"><code>value</code></em></code></span></dt><dd><p>
Sets a named run-time parameter. The configuration parameters
supported by <span class="productname">PostgreSQL</span> are
described in <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a>. Most of the
other command line options are in fact short forms of such a
parameter assignment. <code class="option">-c</code> can appear multiple times
to set multiple parameters.
</p></dd><dt><span class="term"><code class="option">-C <em class="replaceable"><code>name</code></em></code></span></dt><dd><p>
Prints the value of the named run-time parameter, and exits.
(See the <code class="option">-c</code> option above for details.) This can
be used on a running server, and returns values from
<code class="filename">postgresql.conf</code>, modified by any parameters
supplied in this invocation. It does not reflect parameters
supplied when the cluster was started.
</p><p>
This option is meant for other programs that interact with a server
instance, such as <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a>, to query configuration
parameter values. User-facing applications should instead use <a class="xref" href="sql-show.html" title="SHOW"><span class="refentrytitle">SHOW</span></a> or the <code class="structname">pg_settings</code> view.
</p></dd><dt><span class="term"><code class="option">-d <em class="replaceable"><code>debug-level</code></em></code></span></dt><dd><p>
Sets the debug level. The higher this value is set, the more
debugging output is written to the server log. Values are
from 1 to 5. It is also possible to pass <code class="literal">-d
0</code> for a specific session, which will prevent the
server log level of the parent <code class="command">postgres</code> process from being
propagated to this session.
</p></dd><dt><span class="term"><code class="option">-D <em class="replaceable"><code>datadir</code></em></code></span></dt><dd><p>
Specifies the file system location of the database
configuration files. See
<a class="xref" href="runtime-config-file-locations.html" title="19.2. File Locations">Section 19.2</a> for details.
</p></dd><dt><span class="term"><code class="option">-e</code></span></dt><dd><p>
Sets the default date style to <span class="quote">“<span class="quote">European</span>”</span>, that is
<code class="literal">DMY</code> ordering of input date fields. This also causes
the day to be printed before the month in certain date output formats.
See <a class="xref" href="datatype-datetime.html" title="8.5. Date/Time Types">Section 8.5</a> for more information.
</p></dd><dt><span class="term"><code class="option">-F</code></span></dt><dd><p>
Disables <code class="function">fsync</code> calls for improved
performance, at the risk of data corruption in the event of a
system crash. Specifying this option is equivalent to
disabling the <a class="xref" href="runtime-config-wal.html#GUC-FSYNC">fsync</a> configuration
parameter. Read the detailed documentation before using this!
</p></dd><dt><span class="term"><code class="option">-h <em class="replaceable"><code>hostname</code></em></code></span></dt><dd><p>
Specifies the IP host name or address on which
<code class="command">postgres</code> is to listen for TCP/IP
connections from client applications. The value can also be a
comma-separated list of addresses, or <code class="literal">*</code> to specify
listening on all available interfaces. An empty value
specifies not listening on any IP addresses, in which case
only Unix-domain sockets can be used to connect to the
server. Defaults to listening only on
<span class="systemitem">localhost</span>.
Specifying this option is equivalent to setting the <a class="xref" href="runtime-config-connection.html#GUC-LISTEN-ADDRESSES">listen_addresses</a> configuration parameter.
</p></dd><dt><span class="term"><code class="option">-i</code></span></dt><dd><p>
Allows remote clients to connect via TCP/IP (Internet domain)
connections. Without this option, only local connections are
accepted. This option is equivalent to setting
<code class="varname">listen_addresses</code> to <code class="literal">*</code> in
<code class="filename">postgresql.conf</code> or via <code class="option">-h</code>.
</p><p>
This option is deprecated since it does not allow access to the
full functionality of <a class="xref" href="runtime-config-connection.html#GUC-LISTEN-ADDRESSES">listen_addresses</a>.
It's usually better to set <code class="varname">listen_addresses</code> directly.
</p></dd><dt><span class="term"><code class="option">-k <em class="replaceable"><code>directory</code></em></code></span></dt><dd><p>
Specifies the directory of the Unix-domain socket on which
<code class="command">postgres</code> is to listen for
connections from client applications. The value can also be a
comma-separated list of directories. An empty value
specifies not listening on any Unix-domain sockets, in which case
only TCP/IP sockets can be used to connect to the server.
The default value is normally
<code class="filename">/tmp</code>, but that can be changed at build time.
Specifying this option is equivalent to setting the <a class="xref" href="runtime-config-connection.html#GUC-UNIX-SOCKET-DIRECTORIES">unix_socket_directories</a> configuration parameter.
</p></dd><dt><span class="term"><code class="option">-l</code></span></dt><dd><p>
Enables secure connections using <acronym class="acronym">SSL</acronym>.
<span class="productname">PostgreSQL</span> must have been compiled with
support for <acronym class="acronym">SSL</acronym> for this option to be
available. For more information on using <acronym class="acronym">SSL</acronym>,
refer to <a class="xref" href="ssl-tcp.html" title="18.9. Secure TCP/IP Connections with SSL">Section 18.9</a>.
</p></dd><dt><span class="term"><code class="option">-N <em class="replaceable"><code>max-connections</code></em></code></span></dt><dd><p>
Sets the maximum number of client connections that this
server will accept. The default value of this parameter is chosen
automatically by <span class="application">initdb</span>.
Specifying this option is equivalent to setting the
<a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a> configuration parameter.
</p></dd><dt><span class="term"><code class="option">-o <em class="replaceable"><code>extra-options</code></em></code></span></dt><dd><p>
The command-line-style arguments specified in <em class="replaceable"><code>extra-options</code></em> are passed to
all server processes started by this
<code class="command">postgres</code> process.
</p><p>
Spaces within <em class="replaceable"><code>extra-options</code></em> are
considered to separate arguments, unless escaped with a backslash
(<code class="literal">\</code>); write <code class="literal">\\</code> to represent a literal
backslash. Multiple arguments can also be specified via multiple
uses of <code class="option">-o</code>.
</p><p>
The use of this option is obsolete; all command-line options
for server processes can be specified directly on the
<code class="command">postgres</code> command line.
</p></dd><dt><span class="term"><code class="option">-p <em class="replaceable"><code>port</code></em></code></span></dt><dd><p>
Specifies the TCP/IP port or local Unix domain socket file
extension on which <code class="command">postgres</code>
is to listen for connections from client applications.
Defaults to the value of the <code class="envar">PGPORT</code> environment
variable, or if <code class="envar">PGPORT</code> is not set, then
defaults to the value established during compilation (normally
5432). If you specify a port other than the default port,
then all client applications must specify the same port using
either command-line options or <code class="envar">PGPORT</code>.
</p></dd><dt><span class="term"><code class="option">-s</code></span></dt><dd><p>
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.
</p></dd><dt><span class="term"><code class="option">-S</code> <em class="replaceable"><code>work-mem</code></em></span></dt><dd><p>
Specifies the base amount of memory to be used by sorts and
hash tables before resorting to temporary disk files. See the
description of the <code class="varname">work_mem</code> configuration
parameter in <a class="xref" href="runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-MEMORY" title="19.4.1. Memory">Section 19.4.1</a>.
</p></dd><dt><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span></dt><dd><p>
Print the <span class="application">postgres</span> version and exit.
</p></dd><dt><span class="term"><code class="option">--<em class="replaceable"><code>name</code></em>=<em class="replaceable"><code>value</code></em></code></span></dt><dd><p>
Sets a named run-time parameter; a shorter form of
<code class="option">-c</code>.
</p></dd><dt><span class="term"><code class="option">--describe-config</code></span></dt><dd><p>
This option dumps out the server's internal configuration variables,
descriptions, and defaults in tab-delimited <code class="command">COPY</code> format.
It is designed primarily for use by administration tools.
</p></dd><dt><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span></dt><dd><p>
Show help about <span class="application">postgres</span> command line
arguments, and exit.
</p></dd></dl></div></div><div class="refsect2" id="id-1.9.5.14.6.4"><h3>Semi-Internal Options</h3><p>
The options described here are used
mainly for debugging purposes, and in some cases to assist with
recovery of severely damaged databases. There should be no reason
to use them in a production database setup. They are listed
here only for use by <span class="productname">PostgreSQL</span>
system developers. Furthermore, these options might
change or be removed in a future release without notice.
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-f</code> <code class="literal">{ s | i | o | b | t | n | m | h }</code></span></dt><dd><p>
Forbids the use of particular scan and join methods:
<code class="literal">s</code> and <code class="literal">i</code>
disable sequential and index scans respectively,
<code class="literal">o</code>, <code class="literal">b</code> and <code class="literal">t</code>
disable index-only scans, bitmap index scans, and TID scans
respectively, while
<code class="literal">n</code>, <code class="literal">m</code>, and <code class="literal">h</code>
disable nested-loop, merge and hash joins respectively.
</p><p>
Neither sequential scans nor nested-loop joins can be disabled
completely; the <code class="literal">-fs</code> and
<code class="literal">-fn</code> options simply discourage the optimizer
from using those plan types if it has any other alternative.
</p></dd><dt><span class="term"><code class="option">-n</code></span></dt><dd><p>
This option is for debugging problems that cause a server
process to die abnormally. The ordinary strategy in this
situation is to notify all other server processes that they
must terminate and then reinitialize the shared memory and
semaphores. This is because an errant server process could
have corrupted some shared state before terminating. This
option specifies that <code class="command">postgres</code> will
not reinitialize shared data structures. A knowledgeable
system programmer can then use a debugger to examine shared
memory and semaphore state.
</p></dd><dt><span class="term"><code class="option">-O</code></span></dt><dd><p>
Allows the structure of system tables to be modified. This is
used by <code class="command">initdb</code>.
</p></dd><dt><span class="term"><code class="option">-P</code></span></dt><dd><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.
</p></dd><dt><span class="term"><code class="option">-t</code> <code class="literal">pa[rser] | pl[anner] | e[xecutor]</code></span></dt><dd><p>
Print timing statistics for each query relating to each of the
major system modules. This option cannot be used together
with the <code class="option">-s</code> option.
</p></dd><dt><span class="term"><code class="option">-T</code></span></dt><dd><p>
This option is for debugging problems that cause a server
process to die abnormally. The ordinary strategy in this
situation is to notify all other server processes that they
must terminate and then reinitialize the shared memory and
semaphores. This is because an errant server process could
have corrupted some shared state before terminating. This
option specifies that <code class="command">postgres</code> will
stop all other server processes by sending the signal
<code class="literal">SIGSTOP</code>, but will not cause them to
terminate. This permits system programmers to collect core
dumps from all server processes by hand.
</p></dd><dt><span class="term"><code class="option">-v</code> <em class="replaceable"><code>protocol</code></em></span></dt><dd><p>
Specifies the version number of the frontend/backend protocol
to be used for a particular session. This option is for
internal use only.
</p></dd><dt><span class="term"><code class="option">-W</code> <em class="replaceable"><code>seconds</code></em></span></dt><dd><p>
A delay of this many seconds occurs when a new server process
is started, after it conducts the authentication procedure.
This is intended to give an opportunity to attach to the
server process with a debugger.
</p></dd></dl></div></div><div class="refsect2" id="id-1.9.5.14.6.5"><h3>Options for Single-User Mode</h3><a id="id-1.9.5.14.6.5.2" class="indexterm"></a><p>
The following options only apply to the single-user mode
(see <a class="xref" href="app-postgres.html#APP-POSTGRES-SINGLE-USER" title="Single-User Mode">Single-User Mode</a> below).
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--single</code></span></dt><dd><p>
Selects the single-user mode. This must be the first argument
on the command line.
</p></dd><dt><span class="term"><em class="replaceable"><code>database</code></em></span></dt><dd><p>
Specifies the name of the database to be accessed. This must be
the last argument on the command line. If it is
omitted it defaults to the user name.
</p></dd><dt><span class="term"><code class="option">-E</code></span></dt><dd><p>
Echo all commands to standard output before executing them.
</p></dd><dt><span class="term"><code class="option">-j</code></span></dt><dd><p>
Use semicolon followed by two newlines, rather than just newline,
as the command entry terminator.
</p></dd><dt><span class="term"><code class="option">-r</code> <em class="replaceable"><code>filename</code></em></span></dt><dd><p>
Send all server log output to <em class="replaceable"><code>filename</code></em>. This option is only
honored when supplied as a command-line option.
</p></dd></dl></div></div></div><div class="refsect1" id="id-1.9.5.14.7"><h2>Environment</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">PGCLIENTENCODING</code></span></dt><dd><p>
Default character encoding used by clients. (The clients can
override this individually.) This value can also be set in the
configuration file.
</p></dd><dt><span class="term"><code class="envar">PGDATA</code></span></dt><dd><p>
Default data directory location
</p></dd><dt><span class="term"><code class="envar">PGDATESTYLE</code></span></dt><dd><p>
Default value of the <a class="xref" href="runtime-config-client.html#GUC-DATESTYLE">DateStyle</a> run-time
parameter. (The use of this environment variable is deprecated.)
</p></dd><dt><span class="term"><code class="envar">PGPORT</code></span></dt><dd><p>
Default port number (preferably set in the configuration file)
</p></dd></dl></div></div><div class="refsect1" id="id-1.9.5.14.8"><h2>Diagnostics</h2><p>
A failure message mentioning <code class="literal">semget</code> or
<code class="literal">shmget</code> probably indicates you need to configure your
kernel to provide adequate shared memory and semaphores. For more
discussion see <a class="xref" href="kernel-resources.html" title="18.4. Managing Kernel Resources">Section 18.4</a>. You might be able
to postpone reconfiguring your kernel by decreasing <a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a> to reduce the shared memory
consumption of <span class="productname">PostgreSQL</span>, and/or by reducing
<a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a> to reduce the semaphore
consumption.
</p><p>
A failure message suggesting that another server is already running
should be checked carefully, for example by using the command
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>ps ax | grep postgres</code></strong>
</pre><p>
or
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>ps -ef | grep postgres</code></strong>
</pre><p>
depending on your system. If you are certain that no conflicting
server is running, you can remove the lock file mentioned in the
message and try again.
</p><p>
A failure message indicating inability to bind to a port might
indicate that that port is already in use by some
non-<span class="productname">PostgreSQL</span> process. You might also
get this error if you terminate <code class="command">postgres</code>
and immediately restart it using the same port; in this case, you
must simply wait a few seconds until the operating system closes
the port before trying again. Finally, you might get this error if
you specify a port number that your operating system considers to
be reserved. For example, many versions of Unix consider port
numbers under 1024 to be <span class="quote">“<span class="quote">trusted</span>”</span> and only permit
the Unix superuser to access them.
</p></div><div class="refsect1" id="id-1.9.5.14.9"><h2>Notes</h2><p>
The utility command <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a> can be used to
start and shut down the <code class="command">postgres</code> server
safely and comfortably.
</p><p>
If at all possible, <span class="emphasis"><em>do not</em></span> use
<code class="literal">SIGKILL</code> to kill the main
<code class="command">postgres</code> server. Doing so will prevent
<code class="command">postgres</code> from freeing the system
resources (e.g., shared memory and semaphores) that it holds before
terminating. This might cause problems for starting a fresh
<code class="command">postgres</code> run.
</p><p>
To terminate the <code class="command">postgres</code> server normally, the
signals <code class="literal">SIGTERM</code>, <code class="literal">SIGINT</code>, or
<code class="literal">SIGQUIT</code> can be used. The first will wait for
all clients to terminate before quitting, the second will
forcefully disconnect all clients, and the third will quit
immediately without proper shutdown, resulting in a recovery run
during restart.
</p><p>
The <code class="literal">SIGHUP</code> signal will reload
the server configuration files. It is also possible to send
<code class="literal">SIGHUP</code> to an individual server process, but that
is usually not sensible.
</p><p>
To cancel a running query, send the <code class="literal">SIGINT</code> signal
to the process running that command. To terminate a backend process
cleanly, send <code class="literal">SIGTERM</code> to that process. See
also <code class="function">pg_cancel_backend</code> and <code class="function">pg_terminate_backend</code>
in <a class="xref" href="functions-admin.html#FUNCTIONS-ADMIN-SIGNAL" title="9.27.2. Server Signaling Functions">Section 9.27.2</a> for the SQL-callable equivalents
of these two actions.
</p><p>
The <code class="command">postgres</code> server uses <code class="literal">SIGQUIT</code>
to tell subordinate server processes to terminate without normal
cleanup.
This signal <span class="emphasis"><em>should not</em></span> be used by users. It
is also unwise to send <code class="literal">SIGKILL</code> to a server
process — the main <code class="command">postgres</code> process will
interpret this as a crash and will force all the sibling processes
to quit as part of its standard crash-recovery procedure.
</p></div><div class="refsect1" id="APP-POSTGRES-BUGS"><h2>Bugs</h2><p>
The <code class="option">--</code> options will not work on <span class="systemitem">FreeBSD</span> or <span class="systemitem">OpenBSD</span>.
Use <code class="option">-c</code> instead. This is a bug in the affected operating
systems; a future release of <span class="productname">PostgreSQL</span>
will provide a workaround if this is not fixed.
</p></div><div class="refsect1" id="APP-POSTGRES-SINGLE-USER"><h2>Single-User Mode</h2><p>
To start a single-user mode server, use a command like
</p><pre class="screen">
<strong class="userinput"><code>postgres --single -D /usr/local/pgsql/data <em class="replaceable"><code>other-options</code></em> my_database</code></strong>
</pre><p>
Provide the correct path to the database directory with <code class="option">-D</code>, or
make sure that the environment variable <code class="envar">PGDATA</code> is set.
Also specify the name of the particular database you want to work in.
</p><p>
Normally, the single-user mode server treats newline as the command
entry terminator; there is no intelligence about semicolons,
as there is in <span class="application">psql</span>. To continue a command
across multiple lines, you must type backslash just before each
newline except the last one. The backslash and adjacent newline are
both dropped from the input command. Note that this will happen even
when within a string literal or comment.
</p><p>
But if you use the <code class="option">-j</code> command line switch, a single newline
does not terminate command entry; instead, the sequence
semicolon-newline-newline does. That is, type a semicolon immediately
followed by a completely empty line. Backslash-newline is not
treated specially in this mode. Again, there is no intelligence about
such a sequence appearing within a string literal or comment.
</p><p>
In either input mode, if you type a semicolon that is not just before or
part of a command entry terminator, it is considered a command separator.
When you do type a command entry terminator, the multiple statements
you've entered will be executed as a single transaction.
</p><p>
To quit the session, type <acronym class="acronym">EOF</acronym>
(<span class="keycap"><strong>Control</strong></span>+<span class="keycap"><strong>D</strong></span>, usually).
If you've entered any text since the last command entry terminator,
then <acronym class="acronym">EOF</acronym> will be taken as a command entry terminator,
and another <acronym class="acronym">EOF</acronym> will be needed to exit.
</p><p>
Note that the single-user mode server does not provide sophisticated
line-editing features (no command history, for example).
Single-user mode also does not do any background processing, such as
automatic checkpoints or replication.
</p></div><div class="refsect1" id="APP-POSTGRES-EXAMPLES"><h2>Examples</h2><p>
To start <code class="command">postgres</code> in the background
using default values, type:
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>nohup postgres >logfile 2>&1 </dev/null &</code></strong>
</pre><p>
</p><p>
To start <code class="command">postgres</code> with a specific
port, e.g., 1234:
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>postgres -p 1234</code></strong>
</pre><p>
To connect to this server using <span class="application">psql</span>, specify this port with the -p option:
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>psql -p 1234</code></strong>
</pre><p>
or set the environment variable <code class="envar">PGPORT</code>:
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>export PGPORT=1234</code></strong>
<code class="prompt">$</code> <strong class="userinput"><code>psql</code></strong>
</pre><p>
</p><p>
Named run-time parameters can be set in either of these styles:
</p><pre class="screen">
<code class="prompt">$</code> <strong class="userinput"><code>postgres -c work_mem=1234</code></strong>
<code class="prompt">$</code> <strong class="userinput"><code>postgres --work-mem=1234</code></strong>
</pre><p>
Either form overrides whatever setting might exist for
<code class="varname">work_mem</code> in <code class="filename">postgresql.conf</code>. Notice that
underscores in parameter names can be written as either underscore
or dash on the command line. Except for short-term experiments,
it's probably better practice to edit the setting in
<code class="filename">postgresql.conf</code> than to rely on a command-line switch
to set a parameter.
</p></div><div class="refsect1" id="id-1.9.5.14.13"><h2>See Also</h2><p>
<a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle">initdb</span></a>,
<a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a>
</p></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgwaldump.html" title="pg_waldump">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="app-postmaster.html" title="postmaster">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span xmlns="http://www.w3.org/1999/xhtml" class="application">pg_waldump</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> <span xmlns="http://www.w3.org/1999/xhtml" class="application">postmaster</span></td></tr></table></div></body></html>
|
