pg_verifybackup — verify the integrity of a base backup of a PostgreSQL cluster
pg_verifybackup
[option
...]
pg_verifybackup is used to check the
integrity of a database cluster backup taken using
pg_basebackup
against a
backup_manifest
generated by the server at the time
of the backup. The backup must be stored in the "plain"
format; a "tar" format backup can be checked after extracting it.
It is important to note that the validation which is performed by pg_verifybackup does not and cannot include every check which will be performed by a running server when attempting to make use of the backup. Even if you use this tool, you should still perform test restores and verify that the resulting databases work as expected and that they appear to contain the correct data. However, pg_verifybackup can detect many problems that commonly occur due to storage problems or user error.
Backup verification proceeds in four stages. First,
pg_verifybackup
reads the
backup_manifest
file. If that file
does not exist, cannot be read, is malformed, or fails verification
against its own internal checksum, pg_verifybackup
will terminate with a fatal error.
Second, pg_verifybackup
will attempt to verify that
the data files currently stored on disk are exactly the same as the data
files which the server intended to send, with some exceptions that are
described below. Extra and missing files will be detected, with a few
exceptions. This step will ignore the presence or absence of, or any
modifications to, postgresql.auto.conf
,
standby.signal
, and recovery.signal
,
because it is expected that these files may have been created or modified
as part of the process of taking the backup. It also won't complain about
a backup_manifest
file in the target directory or
about anything inside pg_wal
, even though these
files won't be listed in the backup manifest. Only files are checked;
the presence or absence of directories is not verified, except
indirectly: if a directory is missing, any files it should have contained
will necessarily also be missing.
Next, pg_verifybackup
will checksum all the files,
compare the checksums against the values in the manifest, and emit errors
for any files for which the computed checksum does not match the
checksum stored in the manifest. This step is not performed for any files
which produced errors in the previous step, since they are already known
to have problems. Files which were ignored in the previous step are also
ignored in this step.
Finally, pg_verifybackup
will use the manifest to
verify that the write-ahead log records which will be needed to recover
the backup are present and that they can be read and parsed. The
backup_manifest
contains information about which
write-ahead log records will be needed, and
pg_verifybackup
will use that information to
invoke pg_waldump
to parse those write-ahead log
records. The --quiet
flag will be used, so that
pg_waldump
will only report errors, without producing
any other output. While this level of verification is sufficient to
detect obvious problems such as a missing file or one whose internal
checksums do not match, they aren't extensive enough to detect every
possible problem that might occur when attempting to recover. For
instance, a server bug that produces write-ahead log records that have
the correct checksums but specify nonsensical actions can't be detected
by this method.
Note that if extra WAL files which are not required to recover the backup
are present, they will not be checked by this tool, although
a separate invocation of pg_waldump
could be used for
that purpose. Also note that WAL verification is version-specific: you
must use the version of pg_verifybackup
, and thus of
pg_waldump
, which pertains to the backup being checked.
In contrast, the data file integrity checks should work with any version
of the server that generates a backup_manifest
file.
pg_verifybackup accepts the following command-line arguments:
-e
--exit-on-error
Exit as soon as a problem with the backup is detected. If this option
is not specified, pg_verifybackup
will continue
checking the backup even after a problem has been detected, and will
report all problems detected as errors.
-i path
--ignore=path
Ignore the specified file or directory, which should be expressed
as a relative path name, when comparing the list of data files
actually present in the backup to those listed in the
backup_manifest
file. If a directory is
specified, this option affects the entire subtree rooted at that
location. Complaints about extra files, missing files, file size
differences, or checksum mismatches will be suppressed if the
relative path name matches the specified path name. This option
can be specified multiple times.
-m path
--manifest-path=path
Use the manifest file at the specified path, rather than one located in the root of the backup directory.
-n
--no-parse-wal
Don't attempt to parse write-ahead log data that will be needed to recover from this backup.
-K
--encryption-key-command=command
If the cluster is encrypted, run this command to retrieve the encryption key. See Chapter 32 for details.
-q
--quiet
Don't print anything when a backup is successfully verified.
-s
--skip-checksums
Do not verify data file checksums. The presence or absence of files and the sizes of those files will still be checked. This is much faster, because the files themselves do not need to be read.
-w path
--wal-directory=path
Try to parse WAL files stored in the specified directory, rather than
in pg_wal
. This may be useful if the backup is
stored in a separate location from the WAL archive.
Other options are also available:
-V
--version
Print the pg_verifybackup version and exit.
-?
--help
Show help about pg_verifybackup command line arguments, and exit.
To create a base backup of the server at mydbserver
and
verify the integrity of the backup:
$
pg_basebackup -h mydbserver -D /usr/local/pgsql/data
$
pg_verifybackup /usr/local/pgsql/data
To create a base backup of the server at mydbserver
, move
the manifest somewhere outside the backup directory, and verify the
backup:
$
pg_basebackup -h mydbserver -D /usr/local/pgsql/backup1234
$
mv /usr/local/pgsql/backup1234/backup_manifest /my/secure/location/backup_manifest.1234
$
pg_verifybackup -m /my/secure/location/backup_manifest.1234 /usr/local/pgsql/backup1234
To verify a backup while ignoring a file that was added manually to the backup directory, and also skipping checksum verification:
$
pg_basebackup -h mydbserver -D /usr/local/pgsql/data
$
edit /usr/local/pgsql/data/note.to.self
$
pg_verifybackup --ignore=note.to.self --skip-checksums /usr/local/pgsql/data