pg_verifybackup
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## pg_verifybackup

pg_verifybackup — verify the integrity of a base backup of a PostgreSQL cluster

## Synopsis

`pg_verifybackup` [`option`...]

## Description

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 may be stored either in the "plain" or the "tar" format; this includes tar-format backups compressed with any algorithm supported by pg_basebackup. However, at present, `WAL` verification is supported only for plain-format backups. Therefore, if the backup is stored in tar-format, the `-n, --no-parse-wal` option should be used.

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, fails to match the system identifier with `pg_control` of the backup directory 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.

## Options

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.

`-F `format``
`--format=`format``

  Specifies the format of the backup. `format` can be one of the following:

  `p`
  `plain`

    Backup consists of plain files with the same layout as the source server's data directory and tablespaces.

  `t`
  `tar`

    Backup consists of tar files, which may be compressed. A valid backup includes the main data directory in a file named `base.tar`, the WAL files in `pg_wal.tar`, and separate tar files for each tablespace, named after the tablespace's OID. If the backup is compressed, the relevant compression extension is added to the end of each file name.

`-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.

`-P`
`--progress`

  Enable progress reporting. Turning this on will deliver a progress report while verifying checksums.

  This option cannot be used together with the option `--quiet`.

`-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.

## Examples

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

## See Also

pg_basebackup

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