Description
-
pg_basebackup is used to take
base backups of
- a running
PostgreSQL database cluster. The
se - are taken without affecting other clients to the database, and can be used
+
pg_basebackup is used to take
a base backup of
+ a running
PostgreSQL database cluster. The
backup + is taken without affecting other clients of the database, and can be used
both for point-in-time recovery (see
- and as the starting point for a log shipping or streaming replication standby
- servers (see
+ and as the starting point for a log-shipping or streaming- replication standby
+ server (see
-
pg_basebackup makes a
binary copy of the database
- cluster files, while making sure the system is put in and
+
pg_basebackup makes a
n exact copy of the database
+ cluster's files, while making sure the server is put into and
out of backup mode automatically. Backups are always taken of the entire
database cluster; it is not possible to back up individual databases or
- database objects. For individual database backups, a tool such as
+ database objects. For selective backups, another tool such as
The backup is made over a regular
PostgreSQL - connection, and uses the replication protocol. The connection must be made
- with a user having REPLICATION permissions
- (see
- and <filename>pg_hba.conf must explicitly permit the replication
- connection. The server must also be configured
- with leave at leas t
- one session available for the backup and one for WAL streaming (if used).
+ connection that uses the replication protocol. The connection must be made
+ with a user ID that has REPLICATION permissions
+ (see is a superuser,
+ and <link linkend="auth-pg-hba-conf">pg_hba.conf
+ must permit the replication connection. The server must also be configured
+ with provide a t
+ least one walsender for the backup plus one for WAL streaming (if used).
- There can be multiple pg_basebackup s running at the same time, but it is
+ There can be multiple pg_basebackup s running at the same time, but it is usually
better from a performance point of view to take only one backup, and copy
the result.
pg_basebackup can make a base backup from
- not only the primary but also the standby. To take a backup from the standby,
+ not only a primary server but also a standby. To take a backup from a standby,
set up the standby so that it can accept replication connections (that is, set
max_wal_senders and
- and configure host-based authentication
+ and configure its pg_hba.conf appropriately ).
You will also need to enable
- Note that there are some limitations in an online backup from the standby:
+ Note that there are some limitations in taking a backup from a standby:
- If the standby is promoted to the primary during online backup, the backup fails.
+ If the standby is promoted to be primary during backup, the backup fails.
Whenever
pg_basebackup is taking a base
- backup, the pg_stat_progress_basebackup
+ backup, the server's pg_stat_progress_basebackup
view will report the progress of the backup.
See
The following command-line options control the location and format of the
- output.
+ output:
--pgdata=directory
- D irectory to write the output to.
-
pg_basebackup will create th
e directory and - any parent directories if necessary. The directory may already exist,
- but it is an error if the directory already exists and is not empty.
+ Sets the target d irectory to write the output to.
+
pg_basebackup will create th
is directory + (and any missing parent directories) if it does not exist. If it
+ already exists, it must be empty.
- When the backup is in tar mode, and the directory is specified as
- - (dash), the tar file will be written to
- stdout .
+ When the backup is in tar format, the target directory may be
+ specified as - (dash), causing the tar file to be
+ written to stdout .
This option is required.
Write the output as plain files, with the same layout as the
- current data directory and tablespaces. When the cluster has
+ source server's data directory and tablespaces. When the cluster has
no additional tablespaces, the whole database will be placed in
the target directory. If the cluster contains additional
tablespaces, the main data directory will be placed in the
target directory, but all other tablespaces will be placed
- in the same absolute path as they have on the server.
+ in the same absolute path as they have on the source s erver.
This is the default format.
Write the output as tar files in the target directory. The main
- data directory will be written to a file named
- base.tar , and all other tablespaces will
- be named after the tablespace OID.
-
+ data directory's contents will be written to a file named
+ base.tar , and each other tablespace will be
+ written to a separate tar file named after that tablespace's OID.
+
- If the value - (dash) is specified as
- target directory , the tar contents will be written to
- standard output, suitable for piping to for example
-
gzip . This is only
possible if
+ If the target directory is specified as -
+ (dash) , the tar contents will be written to
+ standard output, suitable for piping to (for example)
+
gzip . This is only
allowed if
the cluster has no additional tablespaces and WAL
streaming is not used.
-
- -r rate
- --max-rate=rate
-
- The maximum transfer rate of data transferred from the server. Values are
- in kilobytes per second. Use a suffix of M to indicate megabytes
- per second. A suffix of k is also accepted, and has no effect.
- Valid values are between 32 kilobytes per second and 1024 megabytes per second.
-
- The purpose is to limit the impact of
pg_basebackup - on the running server.
-
- This option always affects transfer of the data directory. Transfer of
- WAL files is only affected if the collection method is fetch .
-
-
-
-
-R
--write-recovery-conf
- Create standby.signal and append connection settings
- to postgresql.auto.conf in the output
- directory (or into the base archive file when using tar format) to
- ease setting up a standby server.
+ Creates a standby.signal file and appends
+ connection settings to the postgresql.auto.conf
+ file in the target directory (or within the base archive file when
+ using tar format). This eases setting up a standby server using the
+ results of the backup.
+
The postgresql.auto.conf file will record the connection
settings and, if specified, the replication slot
- that
pg_basebackup is using, so that
the + that
pg_basebackup is using, so that
streaming replication will use the same settings later on.
--tablespace-mapping=olddir=newdir
- Relocate the tablespace in directory olddir
+ Relocates the tablespace in directory olddir
to newdir during the backup. To be
effective, olddir must exactly match the
- path specification of the tablespace as it is currently defined. (But
- it is not an error if there is no tablespace
- in olddir contained in the backup.)
+ path specification of the tablespace as it is defined on the source
+ server. (But it is not an error if there is no tablespace
+ in olddir on the source server.)
+ Meanwhile newdir is a directory in the
+ receiving host's filesystem. As with the main target directory,
+ newdir need not exist already, but if
+ it does exist it must be empty.
Both olddir
- and newdir must be absolute paths. If a
- path happens to contain a = sign, escape it with a
- backslash. This option can be specified multiple times for multiple
- tablespaces. See examples below .
+ and newdir must be absolute paths. If
+ either path needs to contain an equal sign (= ),
+ precede that with a backslash. This option can be specified multiple
+ times for multiple tablespaces .
--waldir=waldir
- Specifies the location for the write-ahead log directory.
+ Sets the directory to write WAL (write-ahead log) files to.
+ By default WAL files will be placed in
+ the pg_wal subdirectory of the target
+ directory, but this option can be used to place them elsewhere.
waldir must be an absolute path.
- The write-ahead log directory can only be specified when
- the backup is in plain mode.
+ As with the main target directory,
+ waldir need not exist already, but if
+ it does exist it must be empty.
+ This option can only be specified when
+ the backup is in plain format.
--wal-method=method
- Includes the required write-ahead log files (WAL files) in the
+ Includes the required WAL (write-ahead log) files in the
backup. This will include all write-ahead logs generated during
the backup. Unless the method none is specified,
- it is possible to start a postmaster directly in the extracted
+ it is possible to start a postmaster in the target
directory without the need to consult the log archive, thus
- making this a completely standalone backup.
+ making the output a completely standalone backup.
- The following methods for collecting the write-ahead logs ar e
- supported:
+ The following method s for collecting th
+ write-ahead logs are supported:
none
- Don't include write-ahead log in the backup.
+ Don't include write-ahead logs in the backup.
The write-ahead log files are collected at the end of the backup.
- Therefore, it is necessary for the
+ Therefore, it is necessary for the source server's
- enough that the log is not removed before the end of the backup.
- If the log has been rotated when it's time to transfer it, the
- backup will fail and be unusable.
+ enough that the required log data is not removed before the end
+ of the backup. If the required log data has been recycled
+ before it's time to transfer it, the backup will fail and be
+ unusable.
- When tar format mode is used, the write-ahead log files will be
- written to the base.tar file.
+ When tar format is used, the write-ahead log files will be
+ included in the base.tar file.
stream
- Stream the write-ahead log while the backup is created. This will
- open a second connection to the server and start streaming the
- write-ahead log in parallel while running the backup. Therefore,
- it will use up two connections configured by the
-
- client can keep up with write-ahead log received, using this mode
- requires no extra write-ahead logs to be saved on the primary .
+ Stream write-ahead log data while the backup is being taken.
+ This method will open a second connection to the server and
+ start streaming the write-ahead log in parallel while running
+ the backup. Therefore, it will require two replication
+ connections not just one. As long as the client can keep up
+ with the write-ahead log data, using this method requires no
+ extra write-ahead logs to be saved on the source server .
- When tar format mode is used, the write-ahead log files will be
+ When tar format is used, the write-ahead log files will be
written to a separate file named pg_wal.tar
(if the server is a version earlier than 10, the file will be named
pg_xlog.tar ).
The following command-line options control the generation of the
- backup and the running of the program.
+ backup and the running of the program:
--checkpoint=fast|spread
- Sets checkpoint mode to fast (immediate) or spread (default) (see
+ Sets checkpoint mode to fast (immediate) or spread (the default)
+ (see
--create-slot
- This option causes creation of a replication slot named by the
- --slot option before starting the backup.
- An error is raised if the slot already exists.
+ Specifies that the replication slot named by the
+ --slot option should be created before starting
+ the backup. An error is raised if the slot already exists.
By default, when pg_basebackup aborts with an
error, it removes any directories it might have created before
- discovering that it cannot finish the job (for example, data directory
- and write-ahead log directory). This option inhibits tidying-up and i s
- thus useful for debugging.
+ discovering that it cannot finish the job (for example, the target
+ directory and write-ahead log directory). This option inhibit s
+ tidying-up and is t hus useful for debugging.
+
+ -r rate
+ --max-rate=rate
+
+ Sets the maximum transfer rate at which data is collected from the
+ source server. This can be useful to limit the impact
+ of
pg_basebackup on the server. Values
+ are in kilobytes per second. Use a suffix of M
+ to indicate megabytes per second. A suffix of k
+ is also accepted, and has no effect. Valid values are between 32
+ kilobytes per second and 1024 megabytes per second.
+
+ This option always affects transfer of the data directory. Transfer of
+ WAL files is only affected if the collection method
+ is fetch .
+
+
+
+
-S slotname
--slot=slotname
This option can only be used together with -X
- stream. It causes the WAL streaming to use the specified
+ stream. It causes WAL streaming to use the specified
replication slot. If the base backup is intended to be used as a
- streaming replication standby using replication slots, it should then
- use the same replication slot name
- in
- the server does not remove any necessary WAL data in the time between
- the end of the base backup and the start of streaming replication.
+ streaming-replication standby using a replication slot, the standby
+ should then use the same replication slot name as
+
+ primary server does not remove any necessary WAL data in the time
+ between the end of the base backup and the start of streaming
+ replication on the new standby.
The specified replication slot has to exist unless the
Using a SHA hash function provides a cryptographically secure digest
of each file for users who wish to verify that the backup has not been
- tampered with, while the CRC32C algorithm provides a checksum which is
- much faster to calculate and good at catching errors due to accidental
+ tampered with, while the CRC32C algorithm provides a checksum that is
+ much faster to calculate; it is good at catching errors due to accidental
changes but is not resistant to targeted modifications. Note that, to
be useful against an adversary who has access to the backup, the backup
manifest would need to be stored securely elsewhere or otherwise
verified not to have been modified since the backup was taken.
- /> can be used to check the
+
integrity of a backup against the backup manifest.
--no-estimate-size
- This option p revents the server from estimating the total
+ P revents the server from estimating the total
amount of backup data that will be streamed, resulting in the
- <literal>backup_total> column in the
- pg_stat_progress_basebackup
- to be NULL .
+ <structfield>backup_total> column in the
+ pg_stat_progress_basebackup view
+ always being NULL .
Without this option, the backup will start by enumerating
Disables generation of a backup manifest. If this option is not
specified, the server will generate and send a backup manifest
- which can be verified using />.
+ which can be verified using
The manifest is a list of every file present in the backup with the
exception of any WAL files that may be included. It also stores the
size, last modification time, and an optional checksum for each file.
--no-slot
- This option p revents the creation of a temporary replication slot
- during the backup even if it's supported by the server .
+ P revents the creation of a temporary replication slot
+ for the backup .
- Temporary replication slots are created by default if no slot name
- is given with the option -S when using log streaming.
+ By default, if log streaming is selected but no slot name is given
+ with the -S option, then a temporary replication
+ slot is created (if supported by the source server).
The main purpose of this option is to allow taking a base backup when
- the server is out of free replication slots. Using replication slots
+ the server has no free replication slots. Using a replication slot
is almost always preferred, because it prevents needed WAL from being
removed by the server during the backup.
By default, checksums are verified and checksum failures will result
in a non-zero exit status. However, the base backup will not be
removed in such a case, as if the --no-clean option
- had been used. Checksum verifications failures will also be reported
+ had been used. Checksum verification failures will also be reported
in the
pg_stat_database view.
- The following command-line options control the database connection parameters.
+ The following command-line options control the connection to the source
+ server:
The option is called --dbname for consistency with other
client applications, but because
pg_basebackup - doesn't connect to any particular database in the cluster, database
+ doesn't connect to any particular database in the cluster, any database
name in the connection string will be ignored.
Specifies the host name of the machine on which the server is
running. If the value begins with a slash, it is used as the
- directory for the Unix domain socket. The default is taken
+ directory for a Unix domain socket. The default is taken
from the PGHOST environment variable, if set,
else a Unix domain socket connection is attempted.
--status-interval=interval
- Specifies the number of seconds between status packets sent back to the
- server. This allows for easier monitoring of the progress from server.
- A value of zero disables the periodic status updates completely,
+ Specifies the number of seconds between status packets sent back to
+ the source server. Smaller values allow more accurate monitoring of
+ backup progress from the server.
+ A value of zero disables periodic status updates completely,
although an update will still be sent when requested by the server, to
- avoid timeout disconnect . The default value is 10 seconds.
+ avoid timeout-based disconnects . The default value is 10 seconds.
--username=username
- U ser name to connect as.
+ Specifies the u ser name to connect as.
--no-password
- Never issue a password prompt. If the server requires
+ Prevents issuing a password prompt. If the server requires
password authentication and a password is not available by
other means such as a .pgpass file, the
connection attempt will fail. This option can be useful in
--password
- Force
pg_basebackup to prompt for a
- password before connecting to a database .
+ Force
s pg_basebackup to prompt for a
+ password before connecting to the source server .
--version
- Print
the pg_basebackup version and exit .
+ Print
s the pg_basebackup version and exits .
--help
- Show help about
pg_basebackup command line
- arguments, and exit.
+ Show
s help about
pg_basebackup command line
+ arguments, and exits .
Notes
- At the beginning of the backup, a checkpoint needs to be written on the
- server the backup is taken from. Especially if the option
- --checkpoint=fast is not used, this can take some time
- during which
pg_basebackup will be appear
- to be idle.
+ At the beginning of the backup, a checkpoint needs to be performed on the
+ source server. This can take some time (especially if the option
+ --checkpoint=fast is not used), during
+ which
pg_basebackup will appear to be idle.
- Tablespaces will in plain format by default be backed up to the same path
- they have on the server, unless the
+ In plain format, tablespaces will be backed up to the same path
+ they have on the source s erver, unless the
option --tablespace-mapping is used. Without
this option, running a plain format base backup on the same host as the
server will not work if tablespaces are in use, because the backup would
- When tar format mode is used, it is the user's responsibility to unpack each
- tar file before starting the PostgreSQL server. If there are additional tablespaces, the
+ When tar format is used, it is the user's responsibility to unpack each
+ tar file before starting a PostgreSQL server that uses the data. If there
+ are additional tablespaces, the
tar files for them need to be unpacked in the correct locations. In this
case the symbolic links for those tablespaces will be created by the server
according to the contents of the tablespace_map file that is
pg_basebackup works with servers of the same
or an older major version, down to 9.1. However, WAL streaming mode (-X
- stream) only works with server version 9.3 and later, and tar format mode
- (--format=tar ) of the current version o nly works with server version 9.5
- or later.
+ stream) only works with server version 9.3 and later, and tar format
+ (--format=tar ) only works with server version 9.5
+ and later.
-
pg_basebackup will preserve group permissions in
- both the plain and tar formats if group
- permissions are enabled on the source cluster.
+
pg_basebackup will preserve group permissions
+ for data files if group permissions are enabled on the source cluster.
projects / postgresql.git / commitdiff