PG_COMBINEBACKUP(1) PostgreSQL 17.6 Documentation PG_COMBINEBACKUP(1)
NAME
pg_combinebackup - reconstruct a full backup from an incremental backup
and dependent backups
SYNOPSIS
pg_combinebackup [option...] [backup_directory...]
DESCRIPTION
pg_combinebackup is used to reconstruct a synthetic full backup from an
incremental backup and the earlier backups upon which it depends.
Specify all of the required backups on the command line from oldest to
newest. That is, the first backup directory should be the path to the
full backup, and the last should be the path to the final incremental
backup that you wish to restore. The reconstructed backup will be
written to the output directory specified by the -o option.
pg_combinebackup will attempt to verify that the backups you specify
form a legal backup chain from which a correct full backup can be
reconstructed. However, it is not designed to help you keep track of
which backups depend on which other backups. If you remove one or more
of the previous backups upon which your incremental backup relies, you
will not be able to restore it. Moreover, pg_combinebackup only attempts
to verify that the backups have the correct relationship to each other,
not that each individual backup is intact; for that, use
pg_verifybackup(1).
Since the output of pg_combinebackup is a synthetic full backup, it can
be used as an input to a future invocation of pg_combinebackup. The
synthetic full backup would be specified on the command line in lieu of
the chain of backups from which it was reconstructed.
OPTIONS
-d
--debug
Print lots of debug logging output on stderr.
-n
--dry-run
The -n/--dry-run option instructs pg_combinebackup to figure out
what would be done without actually creating the target directory or
any output files. It is particularly useful in combination with
--debug.
-N
--no-sync
By default, pg_combinebackup will wait for all files to be written
safely to disk. This option causes pg_combinebackup to return
without waiting, which is faster, but means that a subsequent
operating system crash can leave the output backup corrupt.
Generally, this option is useful for testing but should not be used
when creating a production installation.
-o outputdir
--output=outputdir
Specifies the output directory to which the synthetic full backup
should be written. Currently, this argument is required.
-T olddir=newdir
--tablespace-mapping=olddir=newdir
Relocates the tablespace in directory olddir to newdir during the
backup. olddir is the absolute path of the tablespace as it exists
in the final backup specified on the command line, and newdir is the
absolute path to use for the tablespace in the reconstructed backup.
If either path needs to contain an equal sign (=), precede that with
a backslash. This option can be specified multiple times for
multiple tablespaces.
--clone
Use efficient file cloning (also known as “reflinks” on some
systems) instead of copying files to the new data directory, which
can result in near-instantaneous copying of the data files.
If a backup manifest is not available or does not contain checksum
of the right type, file cloning will be used to copy the file, but
the file will be also read block-by-block for the checksum
calculation.
File cloning is only supported on some operating systems and file
systems. If it is selected but not supported, the pg_combinebackup
run will error. At present, it is supported on Linux (kernel 4.5 or
later) with Btrfs and XFS (on file systems created with reflink
support), and on macOS with APFS.
--copy
Perform regular file copy. This is the default. (See also
--copy-file-range and --clone.)
--copy-file-range
Use the copy_file_range system call for efficient copying. On some
file systems this gives results similar to --clone, sharing physical
disk blocks, while on others it may still copy blocks, but do so via
an optimized path. At present, it is supported on Linux and FreeBSD.
If a backup manifest is not available or does not contain checksum
of the right type, copy_file_range will be used to copy the file,
but the file will be also read block-by-block for the checksum
calculation.
--manifest-checksums=algorithm
Like pg_basebackup(1), pg_combinebackup writes a backup manifest in
the output directory. This option 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.
--no-manifest
Disables generation of a backup manifest. If this option is not
specified, a backup manifest for the reconstructed backup will be
written to the output directory.
--sync-method=method
When set to fsync, which is the default, pg_combinebackup 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_combinebackup 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
--version
Prints the pg_combinebackup version and exits.
-?
--help
Shows help about pg_combinebackup command line arguments, and exits.
LIMITATIONS
pg_combinebackup does not recompute page checksums when writing the
output directory. Therefore, if any of the backups used for
reconstruction were taken with checksums disabled, but the final backup
was taken with checksums enabled, the resulting directory may contain
pages with invalid checksums.
To avoid this problem, taking a new full backup after changing the
checksum state of the cluster using pg_checksums(1) is recommended.
Otherwise, you can disable and then optionally reenable checksums on the
directory produced by pg_combinebackup in order to correct the problem.
ENVIRONMENT
This utility, like most other PostgreSQL utilities, uses the environment
variables supported by libpq (see Section 32.15).
The environment variable PG_COLOR specifies whether to use color in
diagnostic messages. Possible values are always, auto and never.
SEE ALSO
pg_basebackup(1)
PostgreSQL 17.6 2025 PG_COMBINEBACKUP(1)
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