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NAME

       pg_basebackup - take a base backup of a PostgreSQL cluster

SYNOPSIS

       pg_basebackup [option...]

DESCRIPTION

       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 26.3) and as the starting point for a log-shipping or
       streaming-replication standby server (see Section 27.2).

       pg_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(1) must be used.

       The 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 22.2) 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:

       •   The backup history file is not created in the database cluster backed up.

       •   pg_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.

       •   All 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 28.4.5 for details.

OPTIONS

       The following command-line options control the location and format of the output:

       -D directory
       --pgdata=directory
           Sets 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.

           When the backup is in tar format, the target directory may be specified as - (dash),
           causing the tar file to be written to stdout.

           This option is required.

       -F format
       --format=format
           Selects the format for the output.  format can be one of the following:

           p
           plain
               Write 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.

           t
           tar
               Write 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-conf
           Creates a standby.signal

           file and appends connection settings to the postgresql.auto.conf file in the target
           directory (or within the base archive file when using tar format). This eases setting
           up a standby server using the results of the backup.

           The postgresql.auto.conf file will record the connection settings and, if specified,
           the replication slot that pg_basebackup is using, so that streaming replication will
           use the same settings later on.

       -t target
       --target=target
           Instructs 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=newdir
           Relocates the tablespace in directory olddir to newdir during the backup. To be
           effective, olddir must exactly match the path specification of the tablespace as it is
           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.

           Currently, this option only works with plain output format; it is ignored if tar
           format is selected.

       --waldir=waldir
           Sets the directory to write WAL (write-ahead log) files to. By default WAL files will
           be placed in the pg_wal subdirectory of the target directory, but this option can be
           used to place them elsewhere.  waldir must be an absolute path. 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=method
           Includes the required WAL (write-ahead log) files in the backup. This will include all
           write-ahead logs generated during the backup. Unless the method none is specified, it
           is possible to start a postmaster 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:

           n
           none
               Don't include write-ahead logs in the backup.

           f
           fetch
               The 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.

               When tar format is used, the write-ahead log files will be included in the
               base.tar file.

           s
           stream
               Stream write-ahead log data while the backup is being taken. This method will open
               a second connection to the server and start streaming the write-ahead log in
               parallel while running the backup. Therefore, it will require two replication
               connections not just one. As long as the client can keep up with the write-ahead
               log data, using this method requires no extra write-ahead logs to be saved on the
               source server.

               When tar format 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.

       -z
       --gzip
           Enables 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:

       -c {fast|spread}
       --checkpoint={fast|spread}
           Sets checkpoint mode to fast (immediate) or spread (the default) (see Section 26.3.3).

       -C
       --create-slot
           Specifies that the replication slot named by the --slot option should be created
           before starting the backup. An error is raised if the slot already exists.

       -l label
       --label=label
           Sets the label for the backup. If none is specified, a default value of “pg_basebackup
           base backup” will be used.

       -n
       --no-clean
           By default, when pg_basebackup aborts with an error, it removes any directories it
           might have created before discovering that it cannot finish the job (for example, 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
       --no-sync
           By 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
       --progress
           Enables 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=rate
           Sets the maximum transfer rate at which data is collected from the source server. This
           can be useful to limit the impact of pg_basebackup on the server. Values are in
           kilobytes per second. Use a suffix of M to indicate megabytes per second. A suffix of
           k is also accepted, and has no effect. Valid values are between 32 kilobytes per
           second and 1024 megabytes per second.

           This option always affects transfer of the data directory. Transfer of WAL files is
           only affected if the collection method is fetch.

       -S slotname
       --slot=slotname
           This option can only be used together with -X stream. It causes 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.

       -v
       --verbose
           Enables 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.

       --manifest-checksums=algorithm
           Specifies 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.

           pg_verifybackup(1) can be used to check the integrity of a backup against the backup
           manifest.

       --manifest-force-encode
           Forces 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.

       --no-estimate-size
           Prevents 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.

           This option is not allowed when using --progress.

       --no-manifest
           Disables generation of a backup manifest. If this option is not specified, the server
           will generate and send a backup manifest which can be verified using
           pg_verifybackup(1). The manifest is a list of every file present in the backup with
           the exception of any WAL files that may be included. It also stores the size, last
           modification time, and an optional checksum for each file.

       --no-slot
           Prevents the creation of a temporary replication slot for the backup.

           By default, if log streaming is selected but no slot name is given with the -S option,
           then a temporary replication slot is created (if supported by the source server).

           The main purpose of this option is to allow taking a base backup when the server 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.

       --no-verify-checksums
           Disables verification of checksums, if they are enabled on the server the base backup
           is taken from.

           By default, checksums are verified and checksum failures will result in a non-zero
           exit status. However, the base backup will not be removed in such a case, as if the
           --no-clean option had been used. Checksum verification failures will also be reported
           in the pg_stat_database view.

       The following command-line options control the connection to the source server:

       -d connstr
       --dbname=connstr
           Specifies parameters used to connect to the server, as a connection string; these will
           override any conflicting command line options.

           The option is called --dbname for consistency with other client applications, but
           because pg_basebackup doesn't connect to any particular database in the cluster, any
           database name in the connection string will be ignored.

       -h host
       --host=host
           Specifies the host name of the machine on which the server is running. If the value
           begins with a slash, it is used as the directory for 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=port
           Specifies 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=interval
           Specifies the number of seconds between status packets sent back to the source server.
           Smaller values allow more accurate monitoring of backup progress from the server. A
           value of zero disables periodic status updates completely, although an update will
           still be sent when requested by the server, to avoid timeout-based disconnects. The
           default value is 10 seconds.

       -U username
       --username=username
           Specifies the user name to connect as.

       -w
       --no-password
           Prevents issuing a password prompt. If the server requires password authentication and
           a password is not available by other means such as a .pgpass file, the connection
           attempt will fail. This option can be useful in batch jobs and scripts where no user
           is present to enter a password.

       -W
       --password
           Forces pg_basebackup to prompt for a password before connecting to the source server.

           This 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:

       -V
       --version
           Prints the pg_basebackup version and exits.

       -?
       --help
           Shows help about pg_basebackup command line arguments, and exits.

ENVIRONMENT

       This utility, like most other PostgreSQL utilities, uses the environment variables
       supported by libpq (see Section 34.15).

       The environment variable PG_COLOR specifies whether to use color in diagnostic messages.
       Possible values are always, auto and never.

NOTES

       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 55.4 for the precise details.

       In 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.

EXAMPLES

       To create a base backup of the server at mydbserver and store it in the local directory
       /usr/local/pgsql/data:

           $ pg_basebackup -h mydbserver -D /usr/local/pgsql/data

       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:

           $ pg_basebackup -D backup -Ft -z -P

       To create a backup of a single-tablespace local database and compress this with bzip2:

           $ pg_basebackup -D - -Ft -X fetch | bzip2 > backup.tar.bz2

       (This command will fail if there are multiple tablespaces in the database.)

       To 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

       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:

           $ pg_basebackup -D backup -Ft --compress=gzip:9

SEE ALSO

       pg_dump(1), Section 28.4.5