1PG_BASEBACKUP(1) PostgreSQL 11.3 Documentation PG_BASEBACKUP(1)
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6 pg_basebackup - take a base backup of a PostgreSQL cluster
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9 pg_basebackup [option...]
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12 pg_basebackup is used to take base backups of a running PostgreSQL
13 database cluster. These are taken without affecting other clients to
14 the database, and can be used both for point-in-time recovery (see
15 Section 25.3) and as the starting point for a log shipping or streaming
16 replication standby servers (see Section 26.2).
17 pg_basebackup makes a binary copy of the database cluster files, while
19 making sure the system is put in and out of backup mode automatically.
20 Backups are always taken of the entire database cluster; it is not
21 possible to back up individual databases or database objects. For
22 individual database backups, a tool such as pg_dump(1) must be used.
23 The backup is made over a regular PostgreSQL connection, and uses the
25 replication protocol. The connection must be made with a superuser or a
26 user having REPLICATION permissions (see Section 21.2), and pg_hba.conf
27 must explicitly permit the replication connection. The server must also
28 be configured with max_wal_senders set high enough to leave at least
29 one session available for the backup and one for WAL streaming (if
30 used).
31 There can be multiple pg_basebackups running at the same time, but it
33 is better from a performance point of view to take only one backup, and
34 copy the result.
35 pg_basebackup can make a base backup from not only the master but also
37 the standby. To take a backup from the standby, set up the standby so
38 that it can accept replication connections (that is, set
39 max_wal_senders and hot_standby, and configure host-based
40 authentication). You will also need to enable full_page_writes on the
41 master.
42 Note that there are some limitations in an online backup from the
44 standby:
45 · The backup history file is not created in the database cluster
47 backed up.
48 · If you are using -X none, there is no guarantee that all WAL files
50 required for the backup are archived at the end of backup.
51 · If the standby is promoted to the master during online backup, the
53 backup fails.
54 · All WAL records required for the backup must contain sufficient
56 full-page writes, which requires you to enable full_page_writes on
57 the master and not to use a tool like pg_compresslog as
58 archive_command to remove full-page writes from WAL files.
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62 The following command-line options control the location and format of
63 the output.
64 -D directory
66 --pgdata=directory
67 Directory to write the output to. pg_basebackup will create the
68 directory and any parent directories if necessary. The directory
69 may already exist, but it is an error if the directory already
70 exists and is not empty.
71 When the backup is in tar mode, and the directory is specified as -
73 (dash), the tar file will be written to stdout.
74 This option is required.
76 -F format
78 --format=format
79 Selects the format for the output. format can be one of the
80 following:
81 p
83 plain
84 Write the output as plain files, with the same layout as the
85 current data directory and tablespaces. When the cluster has no
86 additional tablespaces, the whole database will be placed in
87 the target directory. If the cluster contains additional
88 tablespaces, the main data directory will be placed in the
89 target directory, but all other tablespaces will be placed in
90 the same absolute path as they have on the server.
91 This is the default format.
93 t
95 tar
96 Write the output as tar files in the target directory. The main
97 data directory will be written to a file named base.tar, and
98 all other tablespaces will be named after the tablespace OID.
99 If the value - (dash) is specified as target directory, the tar
101 contents will be written to standard output, suitable for
102 piping to for example gzip. This is only possible if the
103 cluster has no additional tablespaces and WAL streaming is not
104 used.
105 -r rate
107 --max-rate=rate
108 The maximum transfer rate of data transferred from the server.
109 Values are in kilobytes per second. Use a suffix of M to indicate
110 megabytes per second. A suffix of k is also accepted, and has no
111 effect. Valid values are between 32 kilobytes per second and 1024
112 megabytes per second.
113 The purpose is to limit the impact of pg_basebackup on the running
115 server.
116 This option always affects transfer of the data directory. Transfer
118 of WAL files is only affected if the collection method is fetch.
119 -R
121 --write-recovery-conf
122 Write a minimal recovery.conf in the output directory (or into the
123 base archive file when using tar format) to ease setting up a
124 standby server. The recovery.conf file will record the connection
125 settings and, if specified, the replication slot that pg_basebackup
126 is using, so that the streaming replication will use the same
127 settings later on.
128 -T olddir=newdir
130 --tablespace-mapping=olddir=newdir
131 Relocate the tablespace in directory olddir to newdir during the
132 backup. To be effective, olddir must exactly match the path
133 specification of the tablespace as it is currently defined. (But it
134 is not an error if there is no tablespace in olddir contained in
135 the backup.) Both olddir and newdir must be absolute paths. If a
136 path happens to contain a = sign, escape it with a backslash. This
137 option can be specified multiple times for multiple tablespaces.
138 See examples below.
139 If a tablespace is relocated in this way, the symbolic links inside
141 the main data directory are updated to point to the new location.
142 So the new data directory is ready to be used for a new server
143 instance with all tablespaces in the updated locations.
144 --waldir=waldir
146 Specifies the location for the write-ahead log directory. waldir
147 must be an absolute path. The write-ahead log directory can only be
148 specified when the backup is in plain mode.
149 -X method
151 --wal-method=method
152 Includes the required write-ahead log files (WAL files) in the
153 backup. This will include all write-ahead logs generated during the
154 backup. Unless the method none is specified, it is possible to
155 start a postmaster directly in the extracted directory without the
156 need to consult the log archive, thus making this a completely
157 standalone backup.
158 The following methods for collecting the write-ahead logs are
160 supported:
161 n
163 none
164 Don't include write-ahead log in the backup.
165 f
167 fetch
168 The write-ahead log files are collected at the end of the
169 backup. Therefore, it is necessary for the wal_keep_segments
170 parameter to be set high enough that the log is not removed
171 before the end of the backup. If the log has been rotated when
172 it's time to transfer it, the backup will fail and be unusable.
173 When tar format mode is used, the write-ahead log files will be
175 written to the base.tar file.
176 s
178 stream
179 Stream the write-ahead log while the backup is created. This
180 will open a second connection to the server and start streaming
181 the write-ahead log in parallel while running the backup.
182 Therefore, it will use up two connections configured by the
183 max_wal_senders parameter. As long as the client can keep up
184 with write-ahead log received, using this mode requires no
185 extra write-ahead logs to be saved on the master.
186 When tar format mode is used, the write-ahead log files will be
188 written to a separate file named pg_wal.tar (if the server is a
189 version earlier than 10, the file will be named pg_xlog.tar).
190 This value is the default.
192 -z
195 --gzip
196 Enables gzip compression of tar file output, with the default
197 compression level. Compression is only available when using the tar
198 format, and the suffix .gz will automatically be added to all tar
199 filenames.
200 -Z level
202 --compress=level
203 Enables gzip compression of tar file output, and specifies the
204 compression level (0 through 9, 0 being no compression and 9 being
205 best compression). Compression is only available when using the tar
206 format, and the suffix .gz will automatically be added to all tar
207 filenames.
208 The following command-line options control the generation of the backup
210 and the running of the program.
211 -c fast|spread
213 --checkpoint=fast|spread
214 Sets checkpoint mode to fast (immediate) or spread (default) (see
215 Section 25.3.3).
216 -C
218 --create-slot
219 This option causes creation of a replication slot named by the
220 --slot option before starting the backup. An error is raised if the
221 slot already exists.
222 -l label
224 --label=label
225 Sets the label for the backup. If none is specified, a default
226 value of “pg_basebackup base backup” will be used.
227 -n
229 --no-clean
230 By default, when pg_basebackup aborts with an error, it removes any
231 directories it might have created before discovering that it cannot
232 finish the job (for example, data directory and write-ahead log
233 directory). This option inhibits tidying-up and is thus useful for
234 debugging.
235 Note that tablespace directories are not cleaned up either way.
237 -N
239 --no-sync
240 By default, pg_basebackup will wait for all files to be written
241 safely to disk. This option causes pg_basebackup to return without
242 waiting, which is faster, but means that a subsequent operating
243 system crash can leave the base backup corrupt. Generally, this
244 option is useful for testing but should not be used when creating a
245 production installation.
246 -P
248 --progress
249 Enables progress reporting. Turning this on will deliver an
250 approximate progress report during the backup. Since the database
251 may change during the backup, this is only an approximation and may
252 not end at exactly 100%. In particular, when WAL log is included in
253 the backup, the total amount of data cannot be estimated in
254 advance, and in this case the estimated target size will increase
255 once it passes the total estimate without WAL.
256 When this is enabled, the backup will start by enumerating the size
258 of the entire database, and then go back and send the actual
259 contents. This may make the backup take slightly longer, and in
260 particular it will take longer before the first data is sent.
261 -S slotname
263 --slot=slotname
264 This option can only be used together with -X stream. It causes the
265 WAL streaming to use the specified replication slot. If the base
266 backup is intended to be used as a streaming replication standby
267 using replication slots, it should then use the same replication
268 slot name in recovery.conf. That way, it is ensured that the server
269 does not remove any necessary WAL data in the time between the end
270 of the base backup and the start of streaming replication.
271 The specified replication slot has to exist unless the option -C is
273 also used.
274 If this option is not specified and the server supports temporary
276 replication slots (version 10 and later), then a temporary
277 replication slot is automatically used for WAL streaming.
278 -v
280 --verbose
281 Enables verbose mode. Will output some extra steps during startup
282 and shutdown, as well as show the exact file name that is currently
283 being processed if progress reporting is also enabled.
284 --no-slot
286 This option prevents the creation of a temporary replication slot
287 during the backup even if it's supported by the server.
288 Temporary replication slots are created by default if no slot name
290 is given with the option -S when using log streaming.
291 The main purpose of this option is to allow taking a base backup
293 when the server is out of free replication slots. Using replication
294 slots is almost always preferred, because it prevents needed WAL
295 from being removed by the server during the backup.
296 --no-verify-checksums
298 Disables verification of checksums, if they are enabled on the
299 server the base backup is taken from.
300 By default, checksums are verified and checksum failures will
302 result in a non-zero exit status. However, the base backup will not
303 be removed in such a case, as if the --no-clean option had been
304 used.
305 The following command-line options control the database connection
307 parameters.
308 -d connstr
310 --dbname=connstr
311 Specifies parameters used to connect to the server, as a connection
312 string. See Section 34.1.1 for more information.
313 The option is called --dbname for consistency with other client
315 applications, but because pg_basebackup doesn't connect to any
316 particular database in the cluster, database name in the connection
317 string will be ignored.
318 -h host
320 --host=host
321 Specifies the host name of the machine on which the server is
322 running. If the value begins with a slash, it is used as the
323 directory for the Unix domain socket. The default is taken from the
324 PGHOST environment variable, if set, else a Unix domain socket
325 connection is attempted.
326 -p port
328 --port=port
329 Specifies the TCP port or local Unix domain socket file extension
330 on which the server is listening for connections. Defaults to the
331 PGPORT environment variable, if set, or a compiled-in default.
332 -s interval
334 --status-interval=interval
335 Specifies the number of seconds between status packets sent back to
336 the server. This allows for easier monitoring of the progress from
337 server. A value of zero disables the periodic status updates
338 completely, although an update will still be sent when requested by
339 the server, to avoid timeout disconnect. The default value is 10
340 seconds.
341 -U username
343 --username=username
344 User name to connect as.
345 -w
347 --no-password
348 Never issue a password prompt. If the server requires password
349 authentication and a password is not available by other means such
350 as a .pgpass file, the connection attempt will fail. This option
351 can be useful in batch jobs and scripts where no user is present to
352 enter a password.
353 -W
355 --password
356 Force pg_basebackup to prompt for a password before connecting to a
357 database.
358 This option is never essential, since pg_basebackup will
360 automatically prompt for a password if the server demands password
361 authentication. However, pg_basebackup will waste a connection
362 attempt finding out that the server wants a password. In some cases
363 it is worth typing -W to avoid the extra connection attempt.
364 Other options are also available:
366 -V
368 --version
369 Print the pg_basebackup version and exit.
370 -?
372 --help
373 Show help about pg_basebackup command line arguments, and exit.
374
376 This utility, like most other PostgreSQL utilities, uses the
377 environment variables supported by libpq (see Section 34.14).
378
380 At the beginning of the backup, a checkpoint needs to be written on the
381 server the backup is taken from. Especially if the option
382 --checkpoint=fast is not used, this can take some time during which
383 pg_basebackup will be appear to be idle.
384 The backup will include all files in the data directory and
386 tablespaces, including the configuration files and any additional files
387 placed in the directory by third parties, except certain temporary
388 files managed by PostgreSQL. But only regular files and directories are
389 copied, except that symbolic links used for tablespaces are preserved.
390 Symbolic links pointing to certain directories known to PostgreSQL are
391 copied as empty directories. Other symbolic links and special device
392 files are skipped. See Section 53.4 for the precise details.
393 Tablespaces will in plain format by default be backed up to the same
395 path they have on the server, unless the option --tablespace-mapping is
396 used. Without this option, running a plain format base backup on the
397 same host as the server will not work if tablespaces are in use,
398 because the backup would have to be written to the same directory
399 locations as the original tablespaces.
400 When tar format mode is used, it is the user's responsibility to unpack
402 each tar file before starting the PostgreSQL server. If there are
403 additional tablespaces, the tar files for them need to be unpacked in
404 the correct locations. In this case the symbolic links for those
405 tablespaces will be created by the server according to the contents of
406 the tablespace_map file that is included in the base.tar file.
407 pg_basebackup works with servers of the same or an older major version,
409 down to 9.1. However, WAL streaming mode (-X stream) only works with
410 server version 9.3 and later, and tar format mode (--format=tar) of the
411 current version only works with server version 9.5 or later.
412 pg_basebackup will preserve group permissions in both the plain and tar
414 formats if group permissions are enabled on the source cluster.
415
417 To create a base backup of the server at mydbserver and store it in the
418 local directory /usr/local/pgsql/data:
419 $ pg_basebackup -h mydbserver -D /usr/local/pgsql/data
421 To create a backup of the local server with one compressed tar file for
423 each tablespace, and store it in the directory backup, showing a
424 progress report while running:
425 $ pg_basebackup -D backup -Ft -z -P
427 To create a backup of a single-tablespace local database and compress
429 this with bzip2:
430 $ pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2
432 (This command will fail if there are multiple tablespaces in the
434 database.)
435 To create a backup of a local database where the tablespace in /opt/ts
437 is relocated to ./backup/ts:
438 $ pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts
440
443 pg_dump(1)
444PostgreSQL 11.3 2019 PG_BASEBACKUP(1)