pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
pg_basebackup is used to take base backups of a running PostgreSQL database cluster. These are taken without affecting other clients to the database, and can be used both for point-in-time recovery (see Section\u00a025.3) and as the starting point for a log shipping or streaming replication standby servers (see Section\u00a026.2).
\npg_basebackup makes a binary copy of the database cluster files, while making sure the system is put in 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 pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection, and uses the replication protocol. The connection must be made with a superuser or a user having REPLICATION permissions (see Section\u00a021.2), and pg_hba.conf must explicitly permit the replication connection. The server must also be configured with max_wal_senders set high enough to leave at least one session available for the backup and one for WAL streaming (if used).
There can be multiple pg_basebackups running at the same time, but it is 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 master but also the standby. To take a backup from the standby, set up the standby so that it can accept replication connections (that is, set max_wal_senders and hot_standby, and configure host-based authentication). You will also need to enable full_page_writes on the master.
Note that there are some limitations in an online backup from the standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to the master during online backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the master and not to use a tool like pg_compresslog as archive_command to remove full-page writes from WAL files.
The following command-line options control the location and format of the output.
\n-D directory--pgdata=directoryDirectory to write the output to. pg_basebackup will create the 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.
\nWhen the backup is in tar mode, and the directory is specified as - (dash), the tar file will be written to stdout.
This option is required.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the current 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite 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.
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 the cluster has no additional tablespaces and WAL streaming is not used.
-r rate--max-rate=rateThe 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.
\nThis option always affects transfer of the data directory. Transfer of WAL files is only affected if the collection method is fetch.
-R--write-recovery-confWrite a minimal recovery.conf in the output directory (or into the base archive file when using tar format) to ease setting up a standby server. The recovery.conf file will record the connection settings and, if specified, the replication slot that pg_basebackup is using, so that the streaming replication will use the same settings later on.
-S slotname--slot=slotnameThis option can only be used together with -X stream. It causes the 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 recovery.conf. That way, it is ensured that 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.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n--no-slotThis option prevents the creation of a temporary replication slot during the backup even if it's supported by the server.
\nTemporary replication slots are created by default if no slot name is given with the option -S when using log streaming.
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 is almost always preferred, because it prevents needed WAL from being removed by the server during the backup.
\n-T olddir=newdir--tablespace-mapping=olddir=newdirRelocate 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.) 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.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSpecifies the location for the write-ahead log directory. waldir must be an absolute path. The write-ahead log directory can only be specified when the backup is in plain mode.
-X method--wal-method=methodIncludes the required write-ahead log files (WAL 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 directory without the need to consult the log archive, thus making this a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
\nnnoneDon't include write-ahead log in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the wal_keep_segments parameter to be set high 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.
\nWhen tar format mode is used, the write-ahead log files will be written to the base.tar file.
sstreamStream 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 max_wal_senders parameter. As long as the client can keep up with write-ahead log received, using this mode requires no extra write-ahead logs to be saved on the master.
\nWhen tar format mode 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level--compress=levelEnables gzip compression of tar file output, and specifies the compression level (0 through 9, 0 being no compression and 9 being best compression). Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
The following command-line options control the generation of the backup and the running of the program.
\n-c fast|spread--checkpoint=fast|spreadSets checkpoint mode to fast (immediate) or spread (default) (see Section\u00a025.3.3).
\n-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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 is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
When this is enabled, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\nThe following command-line options control the database connection parameters.
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe 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 name in the connection string will be ignored.
-h host--host=hostSpecifies 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 from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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, although an update will still be sent when requested by the server, to avoid timeout disconnect. The default value is 10 seconds.
\n-U username--username=usernameUser name to connect as.
\n-w--no-passwordNever issue 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForce pg_basebackup to prompt for a password before connecting to a database.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrint the pg_basebackup version and exit.
\n-?--helpShow help about pg_basebackup command line arguments, and exit.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a033.14).
\nAt 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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a052.4 for the precise details.
\nTablespaces will in plain format by default be backed up to the same path they have on the server, 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 have to be written to the same directory locations as the original tablespaces.
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 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 included in the base.tar file.
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 only works with server version 9.5 or later.
To create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
pg_basebackup is used to take base backups of a running PostgreSQL database cluster. These are taken without affecting other clients to the database, and can be used both for point-in-time recovery (see Section\u00a025.3) and as the starting point for a log shipping or streaming replication standby servers (see Section\u00a026.2).
\npg_basebackup makes a binary copy of the database cluster files, while making sure the system is put in 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 pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection, and uses the replication protocol. The connection must be made with a superuser or a user having REPLICATION permissions (see Section\u00a021.2), and pg_hba.conf must explicitly permit the replication connection. The server must also be configured with max_wal_senders set high enough to leave at least one session available for the backup and one for WAL streaming (if used).
There can be multiple pg_basebackups running at the same time, but it is 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 master but also the standby. To take a backup from the standby, set up the standby so that it can accept replication connections (that is, set max_wal_senders and hot_standby, and configure host-based authentication). You will also need to enable full_page_writes on the master.
Note that there are some limitations in an online backup from the standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to the master during online backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the master and not to use a tool like pg_compresslog as archive_command to remove full-page writes from WAL files.
The following command-line options control the location and format of the output.
\n-D directory--pgdata=directoryDirectory to write the output to. pg_basebackup will create the 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.
\nWhen the backup is in tar mode, and the directory is specified as - (dash), the tar file will be written to stdout.
This option is required.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the current 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite 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.
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 the cluster has no additional tablespaces and WAL streaming is not used.
-r rate--max-rate=rateThe 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.
\nThis option always affects transfer of the data directory. Transfer of WAL files is only affected if the collection method is fetch.
-R--write-recovery-confWrite a minimal recovery.conf in the output directory (or into the base archive file when using tar format) to ease setting up a standby server. The recovery.conf file will record the connection settings and, if specified, the replication slot that pg_basebackup is using, so that the streaming replication will use the same settings later on.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocate 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.) 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.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSpecifies the location for the write-ahead log directory. waldir must be an absolute path. The write-ahead log directory can only be specified when the backup is in plain mode.
-X method--wal-method=methodIncludes the required write-ahead log files (WAL 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 directory without the need to consult the log archive, thus making this a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
\nnnoneDon't include write-ahead log in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the wal_keep_segments parameter to be set high 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.
\nWhen tar format mode is used, the write-ahead log files will be written to the base.tar file.
sstreamStream 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 max_wal_senders parameter. As long as the client can keep up with write-ahead log received, using this mode requires no extra write-ahead logs to be saved on the master.
\nWhen tar format mode 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level--compress=levelEnables gzip compression of tar file output, and specifies the compression level (0 through 9, 0 being no compression and 9 being best compression). Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
The following command-line options control the generation of the backup and the running of the program.
\n-c fast|spread--checkpoint=fast|spreadSets checkpoint mode to fast (immediate) or spread (default) (see Section\u00a025.3.3).
\n-C--create-slotThis 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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 is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
When this is enabled, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent.
\n-S slotname--slot=slotnameThis option can only be used together with -X stream. It causes the 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 recovery.conf. That way, it is ensured that 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.
The specified replication slot has to exist unless the option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--no-slotThis option prevents the creation of a temporary replication slot during the backup even if it's supported by the server.
\nTemporary replication slots are created by default if no slot name is given with the option -S when using log streaming.
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 is almost always preferred, because it prevents needed WAL from being removed by the server during the backup.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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.
The following command-line options control the database connection parameters.
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe 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 name in the connection string will be ignored.
-h host--host=hostSpecifies 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 from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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, although an update will still be sent when requested by the server, to avoid timeout disconnect. The default value is 10 seconds.
\n-U username--username=usernameUser name to connect as.
\n-w--no-passwordNever issue 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForce pg_basebackup to prompt for a password before connecting to a database.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrint the pg_basebackup version and exit.
\n-?--helpShow help about pg_basebackup command line arguments, and exit.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a034.14).
\nAt 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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a053.4 for the precise details.
\nTablespaces will in plain format by default be backed up to the same path they have on the server, 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 have to be written to the same directory locations as the original tablespaces.
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 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 included in the base.tar file.
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 only works with server version 9.5 or later.
pg_basebackup will preserve group permissions in both the plain and tar formats if group permissions are enabled on the source cluster.
To create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
pg_basebackup is used to take base backups of a running PostgreSQL database cluster. These are taken without affecting other clients to the database, and can be used both for point-in-time recovery (see Section\u00a025.3) and as the starting point for a log shipping or streaming replication standby servers (see Section\u00a026.2).
\npg_basebackup makes a binary copy of the database cluster files, while making sure the system is put in 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 pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection, and uses the replication protocol. The connection must be made with a superuser or a user having REPLICATION permissions (see Section\u00a021.2), and pg_hba.conf must explicitly permit the replication connection. The server must also be configured with max_wal_senders set high enough to leave at least one session available for the backup and one for WAL streaming (if used).
There can be multiple pg_basebackups running at the same time, but it is 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 master but also the standby. To take a backup from the standby, set up the standby so that it can accept replication connections (that is, set max_wal_senders and hot_standby, and configure host-based authentication). You will also need to enable full_page_writes on the master.
Note that there are some limitations in an online backup from the standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to the master during online backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the master and not to use a tool like pg_compresslog as archive_command to remove full-page writes from WAL files.
The following command-line options control the location and format of the output.
\n-D directory--pgdata=directoryDirectory to write the output to. pg_basebackup will create the 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.
\nWhen the backup is in tar mode, and the directory is specified as - (dash), the tar file will be written to stdout.
This option is required.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the current 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite 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.
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 the cluster has no additional tablespaces and WAL streaming is not used.
-r rate--max-rate=rateThe 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.
\nThis option always affects transfer of the data directory. Transfer of WAL files is only affected if the collection method is fetch.
-R--write-recovery-confCreate standby.signal file 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. The postgresql.auto.conf file will record the connection settings and, if specified, the replication slot that pg_basebackup is using, so that the streaming replication will use the same settings later on.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocate 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.) 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.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSpecifies the location for the write-ahead log directory. waldir must be an absolute path. The write-ahead log directory can only be specified when the backup is in plain mode.
-X method--wal-method=methodIncludes the required write-ahead log files (WAL 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 directory without the need to consult the log archive, thus making this a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
\nnnoneDon't include write-ahead log in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the wal_keep_segments parameter to be set high 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.
\nWhen tar format mode is used, the write-ahead log files will be written to the base.tar file.
sstreamStream 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 max_wal_senders parameter. As long as the client can keep up with write-ahead log received, using this mode requires no extra write-ahead logs to be saved on the master.
\nWhen tar format mode 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level--compress=levelEnables gzip compression of tar file output, and specifies the compression level (0 through 9, 0 being no compression and 9 being best compression). Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
The following command-line options control the generation of the backup and the running of the program.
\n-c fast|spread--checkpoint=fast|spreadSets checkpoint mode to fast (immediate) or spread (default) (see Section\u00a025.3.3).
\n-C--create-slotThis 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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 is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
When this is enabled, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent.
\n-S slotname--slot=slotnameThis option can only be used together with -X stream. It causes the 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 primary_slot_name. That way, it is ensured that 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.
The specified replication slot has to exist unless the option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--no-slotThis option prevents the creation of a temporary replication slot during the backup even if it's supported by the server.
\nTemporary replication slots are created by default if no slot name is given with the option -S when using log streaming.
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 is almost always preferred, because it prevents needed WAL from being removed by the server during the backup.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 in the pg_stat_database view.
The following command-line options control the database connection parameters.
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe 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 name in the connection string will be ignored.
-h host--host=hostSpecifies 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 from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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, although an update will still be sent when requested by the server, to avoid timeout disconnect. The default value is 10 seconds.
\n-U username--username=usernameUser name to connect as.
\n-w--no-passwordNever issue 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForce pg_basebackup to prompt for a password before connecting to a database.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrint the pg_basebackup version and exit.
\n-?--helpShow help about pg_basebackup command line arguments, and exit.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a033.14).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a052.4 for the precise details.
\nTablespaces will in plain format by default be backed up to the same path they have on the server, 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 have to be written to the same directory locations as the original tablespaces.
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 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 included in the base.tar file.
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 only works with server version 9.5 or later.
pg_basebackup will preserve group permissions in both the plain and tar formats if group permissions are enabled on the source cluster.
To create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a025.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a026.2).
\npg_basebackup makes an 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a021.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary and not to use a tool like pg_compresslog as archive_command to remove full-page writes from WAL files.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a027.4.5 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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--write-recovery-confCreates 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 streaming replication will use the same settings later on.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the log archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level--compress=levelEnables gzip compression of tar file output, and specifies the compression level (0 through 9, 0 being no compression and 9 being best compression). Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c fast|spread--checkpoint=fast|spreadSets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a025.3.3).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 that is much faster to calculate; it is good at catching errors due to accidental changes but is not resistant to malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name in the connection string will be ignored.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a033.14).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a052.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
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 (--format=tar) only works with server version 9.5 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a026.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a027.2).
\npg_basebackup makes an 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a022.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary and not to use a tool like pg_compresslog as archive_command to remove full-page writes from WAL files.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a028.4.5 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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--write-recovery-confCreates 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 streaming replication will use the same settings later on.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the log archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level--compress=levelEnables gzip compression of tar file output, and specifies the compression level (0 through 9, 0 being no compression and 9 being best compression). Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c fast|spread--checkpoint=fast|spreadSets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a026.3.3).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 that is much faster to calculate; it is good at catching errors due to accidental changes but is not resistant to malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name in the connection string will be ignored.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a034.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a053.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
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 (--format=tar) only works with server version 9.5 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a026.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a027.2).
\npg_basebackup makes an 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a022.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a028.4.5 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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--write-recovery-confCreates 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 streaming replication will use the same settings later on.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the log archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, or none for no compression. A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level and workers.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a026.3.3).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 that is much faster to calculate; it is good at catching errors due to accidental changes but is not resistant to malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name in the connection string will be ignored.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a034.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a055.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
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 (--format=tar) only works with server version 9.5 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of a local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a026.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a027.2).
\npg_basebackup makes an 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a022.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a028.4.6 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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--write-recovery-confCreates 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 streaming replication will use the same settings later on.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the WAL archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, none for no compression or an integer (no compression if 0, gzip if greater than 0). A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level, long, and workers. The detail string cannot be used when the compression method is specified as a plain integer.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a026.3.3).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 that is much faster to calculate; it is good at catching errors due to accidental changes but is not resistant to malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThe option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name in the connection string will be ignored.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a034.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a055.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
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 (--format=tar) only works with server version 9.5 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of a local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a025.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a026.2).
\npg_basebackup can take a full or incremental base backup of the database. When used to take a full backup, it makes an exact copy of the database cluster's files. When used to take an incremental backup, some files that would have been part of a full backup may be replaced with incremental versions of the same files, containing only those blocks that have been modified since the reference backup. An incremental backup cannot be used directly; instead, pg_combinebackup must first be used to combine it with the previous backups upon which it depends. See Section\u00a025.3.3 for more information about incremental backups, and Section\u00a025.3.5 for steps to recover from a backup.
\nIn any mode, pg_basebackup makes 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a021.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a027.4.6 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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.
-i old_manifest_file--incremental=old_manifest_filePerforms an incremental backup. The backup manifest for the reference backup must be provided, and will be uploaded to the server, which will respond by sending the requested incremental backup.
\n-R--write-recovery-confCreates 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 streaming replication and logical replication slot synchronization will use the same settings later on. The dbname will be recorded only if the dbname was specified explicitly in the connection string or environment variable.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the WAL archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, none for no compression or an integer (no compression if 0, gzip if greater than 0). A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level, long, and workers. The detail string cannot be used when the compression method is specified as a plain integer.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a025.3.4).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n--sync-method=methodWhen set to fsync, which is the default, pg_basebackup will recursively open and synchronize all files in the backup directory. When the plain format is used, the search for files will follow symbolic links for the WAL directory and each configured tablespace.
On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file system that contains the backup directory. When the plain format is used, pg_basebackup will also synchronize the file systems that contain the WAL files and each tablespace. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.
This option has no effect when --no-sync is used.
-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 that is much faster to calculate; it is good at catching errors due to accidental changes but is not resistant to malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThis option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name included in the connection string will be ignored by the server. However, a database name supplied that way overrides the default database name (replication) for purposes of looking up the replication connection's password in ~/.pgpass. Similarly, middleware or proxies used in connecting to PostgreSQL might utilize the name for purposes such as connection routing. The database name can also be used by logical replication slot synchronization.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a032.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a053.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
pg_basebackup works with servers of the same or older major version, down to 9.1. However, WAL streaming mode (-X stream) only works with server version 9.3 and later, the tar format (--format=tar) only works with server version 9.5 and later, and incremental backup (--incremental) only works with server version 17 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of the local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a025.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a026.2).
\npg_basebackup can take a full or incremental base backup of the database. When used to take a full backup, it makes an exact copy of the database cluster's files. When used to take an incremental backup, some files that would have been part of a full backup may be replaced with incremental versions of the same files, containing only those blocks that have been modified since the reference backup. An incremental backup cannot be used directly; instead, pg_combinebackup must first be used to combine it with the previous backups upon which it depends. See Section\u00a025.3.3 for more information about incremental backups, and Section\u00a025.3.5 for steps to recover from a backup.
\nIn any mode, pg_basebackup makes 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a021.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a027.4.6 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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.
-i old_manifest_file--incremental=old_manifest_filePerforms an incremental backup. The backup manifest for the reference backup must be provided, and will be uploaded to the server, which will respond by sending the requested incremental backup.
\n-R--write-recovery-confCreates 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 streaming replication and logical replication slot synchronization will use the same settings later on. The dbname will be recorded only if the dbname was specified explicitly in the connection string or environment variable.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the WAL archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, none for no compression or an integer (no compression if 0, gzip if greater than 0). A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level, long, and workers. The detail string cannot be used when the compression method is specified as a plain integer.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a025.3.4).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n--sync-method=methodWhen set to fsync, which is the default, pg_basebackup will recursively open and synchronize all files in the backup directory. When the plain format is used, the search for files will follow symbolic links for the WAL directory and each configured tablespace.
On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file system that contains the backup directory. When the plain format is used, pg_basebackup will also synchronize the file systems that contain the WAL files and each tablespace. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.
This option has no effect when --no-sync is used.
-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 CRC-32C 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 malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThis option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name included in the connection string will be ignored by the server. However, a database name supplied that way overrides the default database name (replication) for purposes of looking up the replication connection's password in ~/.pgpass. Similarly, middleware or proxies used in connecting to PostgreSQL might utilize the name for purposes such as connection routing. The database name can also be used by logical replication slot synchronization.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a032.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a054.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
pg_basebackup works with servers of the same or older major version, down to 9.1. However, WAL streaming mode (-X stream) only works with server version 9.3 and later, the tar format (--format=tar) only works with server version 9.5 and later, and incremental backup (--incremental) only works with server version 17 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of the local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a025.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a026.2).
\npg_basebackup can take a full or incremental base backup of the database. When used to take a full backup, it makes an exact copy of the database cluster's files. When used to take an incremental backup, some files that would have been part of a full backup may be replaced with incremental versions of the same files, containing only those blocks that have been modified since the reference backup. An incremental backup cannot be used directly; instead, pg_combinebackup must first be used to combine it with the previous backups upon which it depends. See Section\u00a025.3.3 for more information about incremental backups, and Section\u00a025.3.5 for steps to recover from a backup.
\nIn any mode, pg_basebackup makes 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a021.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a027.4.7 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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.
-i old_manifest_file--incremental=old_manifest_filePerforms an incremental backup. The backup manifest for the reference backup must be provided, and will be uploaded to the server, which will respond by sending the requested incremental backup.
\n-R--write-recovery-confCreates 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 streaming replication and logical replication slot synchronization will use the same settings later on. The dbname will be recorded only if the dbname was specified explicitly in the connection string or environment variable.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the WAL archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, none for no compression or an integer (no compression if 0, gzip if greater than 0). A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level, long, and workers. The detail string cannot be used when the compression method is specified as a plain integer.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast or spread (see Section\u00a025.3.4). The default is spread.
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n--sync-method=methodWhen set to fsync, which is the default, pg_basebackup will recursively open and synchronize all files in the backup directory. When the plain format is used, the search for files will follow symbolic links for the WAL directory and each configured tablespace.
On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file system that contains the backup directory. When the plain format is used, pg_basebackup will also synchronize the file systems that contain the WAL files and each tablespace. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.
This option has no effect when --no-sync is used.
-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 CRC-32C 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 malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThis option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name included in the connection string will be ignored by the server. However, a database name supplied that way overrides the default database name (replication) for purposes of looking up the replication connection's password in ~/.pgpass. Similarly, middleware or proxies used in connecting to PostgreSQL might utilize the name for purposes such as connection routing. The database name can also be used by logical replication slot synchronization.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a032.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a054.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
pg_basebackup works with servers of the same or older major version, down to 9.1. However, WAL streaming mode (-X stream) only works with server version 9.3 and later, the tar format (--format=tar) only works with server version 9.5 and later, and incremental backup (--incremental) only works with server version 17 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of the local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a025.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a026.2).
\npg_basebackup can take a full or incremental base backup of the database. When used to take a full backup, it makes an exact copy of the database cluster's files. When used to take an incremental backup, some files that would have been part of a full backup may be replaced with incremental versions of the same files, containing only those blocks that have been modified since the reference backup. An incremental backup cannot be used directly; instead, pg_combinebackup must first be used to combine it with the previous backups upon which it depends. See Section\u00a025.3.3 for more information about incremental backups, and Section\u00a025.3.5 for steps to recover from a backup.
\nIn any mode, pg_basebackup makes 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a021.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a027.4.7 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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.
-i old_manifest_file--incremental=old_manifest_filePerforms an incremental backup. The backup manifest for the reference backup must be provided, and will be uploaded to the server, which will respond by sending the requested incremental backup.
\n-R--write-recovery-confCreates 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 streaming replication and logical replication slot synchronization will use the same settings later on. The dbname will be recorded only if the dbname was specified explicitly in the connection string or environment variable.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the WAL archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, none for no compression or an integer (no compression if 0, gzip if greater than 0). A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level, long, and workers. The detail string cannot be used when the compression method is specified as a plain integer.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast or spread (see Section\u00a025.3.4). The default is spread.
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n--sync-method=methodWhen set to fsync, which is the default, pg_basebackup will recursively open and synchronize all files in the backup directory. When the plain format is used, the search for files will follow symbolic links for the WAL directory and each configured tablespace.
On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file system that contains the backup directory. When the plain format is used, pg_basebackup will also synchronize the file systems that contain the WAL files and each tablespace. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.
This option has no effect when --no-sync is used.
-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 CRC-32C 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 malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
Checksums must be enabled on the server for the duration of the base backup in order to be verified. If checksums are in the process of being enabled when the base backup starts then checksum verification is disabled for the base backup.
\nThe following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThis option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name included in the connection string will be ignored by the server. However, a database name supplied that way overrides the default database name (replication) for purposes of looking up the replication connection's password in ~/.pgpass. Similarly, middleware or proxies used in connecting to PostgreSQL might utilize the name for purposes such as connection routing. The database name can also be used by logical replication slot synchronization.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a032.14).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a054.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
pg_basebackup works with servers of the same or older major version, down to 9.1. However, WAL streaming mode (-X stream) only works with server version 9.3 and later, the tar format (--format=tar) only works with server version 9.5 and later, and incremental backup (--incremental) only works with server version 17 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of the local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n
pg_basebackup \u2014 take a base backup of a PostgreSQL cluster
\npg_basebackup [option...]
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 Section\u00a025.3) and as the starting point for a log-shipping or streaming-replication standby server (see Section\u00a026.2).
\npg_basebackup can take a full or incremental base backup of the database. When used to take a full backup, it makes an exact copy of the database cluster's files. When used to take an incremental backup, some files that would have been part of a full backup may be replaced with incremental versions of the same files, containing only those blocks that have been modified since the reference backup. An incremental backup cannot be used directly; instead, pg_combinebackup must first be used to combine it with the previous backups upon which it depends. See Section\u00a025.3.3 for more information about incremental backups, and Section\u00a025.3.5 for steps to recover from a backup.
\nIn any mode, pg_basebackup makes 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 selective backups, another tool such as pg_dump must be used.
\nThe backup is made over a regular PostgreSQL connection that uses the replication protocol. The connection must be made with a user ID that has REPLICATION permissions (see Section\u00a021.2) or is a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to provide at least one walsender for the backup plus one for WAL streaming (if used).
There can be multiple pg_basebackups 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 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 hot_standby, and configure its pg_hba.conf appropriately). You will also need to enable full_page_writes on the primary.
Note that there are some limitations in taking a backup from a standby:
\nThe backup history file is not created in the database cluster backed up.
\npg_basebackup cannot force the standby to switch to a new WAL file at the end of backup. When you are using -X none, if write activity on the primary is low, pg_basebackup may need to wait a long time for the last WAL file required for the backup to be switched and archived. In this case, it may be useful to run pg_switch_wal on the primary in order to trigger an immediate WAL file switch.
If the standby is promoted to be primary during backup, the backup fails.
\nAll WAL records required for the backup must contain sufficient full-page writes, which requires you to enable full_page_writes on the primary.
Whenever pg_basebackup is taking a base backup, the server's pg_stat_progress_basebackup view will report the progress of the backup. See Section\u00a027.4.6 for details.
The following command-line options control the location and format of the output:
\n-D directory--pgdata=directorySets the target directory to write the output to. pg_basebackup will create this directory (and any missing parent directories) if it does not exist. If it already exists, it must be empty.
\nWhen 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.
\n-F format--format=formatSelects the format for the output. format can be one of the following:
pplainWrite the output as plain files, with the same layout as the 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 source server. (See --tablespace-mapping to change that.)
This is the default format.
\nttarWrite the output as tar files in the target directory. The main 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 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.
-i old_manifest_file--incremental=old_manifest_filePerforms an incremental backup. The backup manifest for the reference backup must be provided, and will be uploaded to the server, which will respond by sending the requested incremental backup.
\n-R--write-recovery-confCreates 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 streaming replication and logical replication slot synchronization will use the same settings later on. The dbname will be recorded only if the dbname was specified explicitly in the connection string or environment variable.
-t target--target=targetInstructs the server where to place the base backup. The default target is client, which specifies that the backup should be sent to the machine where pg_basebackup is running. If the target is instead set to server:/some/path, the backup will be stored on the machine where the server is running in the /some/path directory. Storing a backup on the server requires superuser privileges or having privileges of the pg_write_server_files role. If the target is set to blackhole, the contents are discarded and not stored anywhere. This should only be used for testing purposes, as you will not end up with an actual backup.
Since WAL streaming is implemented by pg_basebackup rather than by the server, this option cannot be used together with -Xstream. Since that is the default, when this option is specified, you must also specify either -Xfetch or -Xnone.
-T olddir=newdir--tablespace-mapping=olddir=newdirRelocates 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 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 either path needs to contain an equal sign (=), precede that with a backslash. This option can be specified multiple times for multiple tablespaces.
If a tablespace is relocated in this way, the symbolic links inside the main data directory are updated to point to the new location. So the new data directory is ready to be used for a new server instance with all tablespaces in the updated locations.
\nCurrently, this option only works with plain output format; it is ignored if tar format is selected.
\n--waldir=waldirSets 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. 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.
-X method--wal-method=methodIncludes 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 in the target directory without the need to consult the WAL archive, thus making the output a completely standalone backup.
The following methods for collecting the write-ahead logs are supported:
nnoneDon't include write-ahead logs in the backup.
\nffetchThe write-ahead log files are collected at the end of the backup. Therefore, it is necessary for the source server's wal_keep_size parameter to be set high 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.
\nWhen tar format is used, the write-ahead log files will be included in the base.tar file.
sstreamStream 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.
\nWhen 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).
This value is the default.
\n-z--gzipEnables gzip compression of tar file output, with the default compression level. Compression is only available when using the tar format, and the suffix .gz will automatically be added to all tar filenames.
-Z level-Z [{client|server}-]method[:detail]--compress=level--compress=[{client|server}-]method[:detail]Requests compression of the backup. If client or server is included, it specifies where the compression is to be performed. Compressing on the server will reduce transfer bandwidth but will increase server CPU consumption. The default is client except when --target is used. In that case, the backup is not being sent to the client, so only server compression is sensible. When -Xstream, which is the default, is used, server-side compression will not be applied to the WAL. To compress the WAL, use client-side compression, or specify -Xfetch.
The compression method can be set to gzip, lz4, zstd, none for no compression or an integer (no compression if 0, gzip if greater than 0). A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or keyword=value. Currently, the supported keywords are level, long, and workers. The detail string cannot be used when the compression method is specified as a plain integer.
If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.
When the tar format is used with gzip, lz4, or zstd, the suffix .gz, .lz4, or .zst, respectively, will be automatically added to all tar filenames. When the plain format is used, client-side compression may not be specified, but it is still possible to request server-side compression. If this is done, the server will compress the backup for transmission, and the client will decompress and extract it.
When this option is used in combination with -Xstream, pg_wal.tar will be compressed using gzip if client-side gzip compression is selected, but will not be compressed if any other compression algorithm is selected, or if server-side compression is selected.
The following command-line options control the generation of the backup and the invocation of the program:
\n-c {fast|spread}--checkpoint={fast|spread}Sets checkpoint mode to fast (immediate) or spread (the default) (see Section\u00a025.3.4).
\n-C--create-slotSpecifies 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.
-l label--label=labelSets the label for the backup. If none is specified, a default value of \u201cpg_basebackup base backup\u201d will be used.
-n--no-cleanBy 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, the target directory and write-ahead log directory). This option inhibits tidying-up and is thus useful for debugging.
Note that tablespace directories are not cleaned up either way.
\n-N--no-syncBy default, pg_basebackup will wait for all files to be written safely to disk. This option causes pg_basebackup to return without waiting, which is faster, but means that a subsequent operating system crash can leave the base backup corrupt. Generally, this option is useful for testing but should not be used when creating a production installation.
-P--progressEnables progress reporting. Turning this on will deliver an approximate progress report during the backup. Since the database may change during the backup, this is only an approximation and may not end at exactly 100%. In particular, when WAL log is included in the backup, the total amount of data cannot be estimated in advance, and in this case the estimated target size will increase once it passes the total estimate without WAL.
-r rate--max-rate=rateSets 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=slotnameThis option can only be used together with -X 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 a replication slot, the standby should then use the same replication slot name as primary_slot_name. This ensures that the 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 option -C is also used.
If this option is not specified and the server supports temporary replication slots (version 10 and later), then a temporary replication slot is automatically used for WAL streaming.
\n--sync-method=methodWhen set to fsync, which is the default, pg_basebackup will recursively open and synchronize all files in the backup directory. When the plain format is used, the search for files will follow symbolic links for the WAL directory and each configured tablespace.
On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file system that contains the backup directory. When the plain format is used, pg_basebackup will also synchronize the file systems that contain the WAL files and each tablespace. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.
This option has no effect when --no-sync is used.
-v--verboseEnables verbose mode. Will output some extra steps during startup and shutdown, as well as show the exact file name that is currently being processed if progress reporting is also enabled.
\n--manifest-checksums=algorithmSpecifies the checksum algorithm that should be applied to each file included in the backup manifest. Currently, the available algorithms are NONE, CRC32C, SHA224, SHA256, SHA384, and SHA512. The default is CRC32C.
If NONE is selected, the backup manifest will not contain any checksums. Otherwise, it will contain a checksum of each file in the backup using the specified algorithm. In addition, the manifest will always contain a SHA256 checksum of its own contents. The SHA algorithms are significantly more CPU-intensive than CRC32C, so selecting one of them may increase the time required to complete the backup.
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 CRC-32C 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 malicious 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.
\npg_verifybackup can be used to check the integrity of a backup against the backup manifest.
\n--manifest-force-encodeForces all filenames in the backup manifest to be hex-encoded. If this option is not specified, only non-UTF8 filenames are hex-encoded. This option is mostly intended to test that tools which read a backup manifest file properly handle this case.
\n--no-estimate-sizePrevents the server from estimating the total amount of backup data that will be streamed, resulting in the backup_total column in the pg_stat_progress_basebackup view always being NULL.
Without this option, the backup will start by enumerating the size of the entire database, and then go back and send the actual contents. This may make the backup take slightly longer, and in particular it will take longer before the first data is sent. This option is useful to avoid such estimation time if it's too long.
\nThis option is not allowed when using --progress.
--no-manifestDisables 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 pg_verifybackup. 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.
\n--no-slotPrevents the creation of a temporary replication slot for the backup.
\nBy 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 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.
\n--no-verify-checksumsDisables verification of checksums, if they are enabled on the server the base backup is taken from.
\nBy 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 verification failures will also be reported in the pg_stat_database view.
The following command-line options control the connection to the source server:
\n-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options.
\nThis option is called --dbname for consistency with other client applications, but because pg_basebackup doesn't connect to any particular database in the cluster, any database name included in the connection string will be ignored by the server. However, a database name supplied that way overrides the default database name (replication) for purposes of looking up the replication connection's password in ~/.pgpass. Similarly, middleware or proxies used in connecting to PostgreSQL might utilize the name for purposes such as connection routing. The database name can also be used by logical replication slot synchronization.
-h host--host=hostSpecifies 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 a Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
-p port--port=portSpecifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
-s interval--status-interval=intervalSpecifies 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-based disconnects. The default value is 10 seconds.
\n-U username--username=usernameSpecifies the user name to connect as.
\n-w--no-passwordPrevents 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 batch jobs and scripts where no user is present to enter a password.
-W--passwordForces pg_basebackup to prompt for a password before connecting to the source server.
\nThis option is never essential, since pg_basebackup will automatically prompt for a password if the server demands password authentication. However, pg_basebackup will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
\n-V--versionPrints the pg_basebackup version and exits.
\n-?--helpShows help about pg_basebackup command line arguments, and exits.
\nThis utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section\u00a032.15).
\nThe environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.
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.
The backup will include all files in the data directory and tablespaces, including the configuration files and any additional files placed in the directory by third parties, except certain temporary files managed by PostgreSQL and operating system files. But only regular files and directories are copied, except that symbolic links used for tablespaces are preserved. Symbolic links pointing to certain directories known to PostgreSQL are copied as empty directories. Other symbolic links and special device files are skipped. See Section\u00a054.4 for the precise details.
\nIn plain format, tablespaces will be backed up to the same path they have on the source server, 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 have to be written to the same directory locations as the original tablespaces.
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 included in the base.tar file.
pg_basebackup works with servers of the same or older major version, down to 9.1. However, WAL streaming mode (-X stream) only works with server version 9.3 and later, the tar format (--format=tar) only works with server version 9.5 and later, and incremental backup (--incremental) only works with server version 17 and later.
pg_basebackup will preserve group permissions for data files if group permissions are enabled on the source cluster.
\nTo create a base backup of the server at mydbserver and store it in the local directory /usr/local/pgsql/data:
\n$pg_basebackup -h mydbserver -D /usr/local/pgsql/data\n
To create a backup of the local server with one compressed tar file for each tablespace, and store it in the directory backup, showing a progress report while running:
\n$pg_basebackup -D backup -Ft -z -P\n
To create a backup of a single-tablespace local database and compress this with bzip2:
\n\n$pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2\n
(This command will fail if there are multiple tablespaces in the database.)
\nTo create a backup of a local database where the tablespace in /opt/ts is relocated to ./backup/ts:
\n$pg_basebackup -D backup/data -T /opt/ts=$(pwd)/backup/ts\n
To create a backup of the local server with one tar file for each tablespace compressed with gzip at level 9, stored in the directory backup:
\n$pg_basebackup -D backup -Ft --compress=gzip:9\n