NAME

       borg-check - Check repository consistency

SYNOPSIS

       borg [common options] check [options] [REPOSITORY_OR_ARCHIVE]

DESCRIPTION

       The check command verifies the consistency of a repository and the corresponding archives.

       check  --repair  is a potentially dangerous function and might lead to data loss (for kinds of corruption
       it is not capable of dealing with). BE VERY CAREFUL!

       First, the underlying repository data files are checked:

       • For all segments, the segment magic header is checked.

       • For all objects stored in the segments, all metadata (e.g. CRC and size) and all data is read. The read
         data is checked by size and CRC. Bit rot and other types of accidental damage can be detected this way.

       • In repair mode, if an integrity error is detected in a segment, try to recover as many objects from the
         segment as possible.

       • In repair mode, make sure that the index is consistent with the data stored in the segments.

       • If checking a remote repo via  ssh:,  the  repo  check  is  executed  on  the  server  without  causing
         significant network traffic.

       • The repository check can be skipped using the --archives-only option.

       Second, the consistency and correctness of the archive metadata is verified:

       • Is the repo manifest present? If not, it is rebuilt from archive metadata chunks (this requires reading
         and decrypting of all metadata and data).

       • Check if archive metadata chunk is present; if not, remove archive from manifest.

       • For all files (items) in the archive, for all chunks referenced by  these  files,  check  if  chunk  is
         present.  In  repair  mode, if a chunk is not present, replace it with a same-size replacement chunk of
         zeroes. If a previously lost chunk reappears (e.g. via a later backup), in  repair  mode  the  all-zero
         replacement  chunk  will  be  replaced  by the correct chunk. This requires reading of archive and file
         metadata, but not data.

       • In repair mode, when all the archives were checked, orphaned chunks are  deleted  from  the  repo.  One
         cause  of  orphaned  chunks  are  input  file related errors (like read errors) in the archive creation
         process.

       • If checking a remote repo via ssh:, the archive check is executed on  the  client  machine  because  it
         requires decryption, and this is always done client-side as key access is needed.

       • The archive checks can be time consuming; they can be skipped using the --repository-only option.

       The  --verify-data option will perform a full integrity verification (as opposed to checking the CRC32 of
       the segment) of data, which means reading the data from the repository, decrypting and decompressing  it.
       This  is  a  cryptographic  verification,  which  will  detect  (accidental)  corruption.  For  encrypted
       repositories it is tamper-resistant as well, unless the attacker has access to the keys. It is also  very
       slow.

OPTIONS

       See borg-common(1) for common options of Borg commands.

   arguments
       REPOSITORY_OR_ARCHIVE
              repository or archive to check consistency of

   optional arguments
       --repository-only
              only perform repository checks

       --archives-only
              only perform archives checks

       --verify-data
              perform cryptographic archive data integrity verification (conflicts with --repository-only)

       --repair
              attempt to repair any inconsistencies found

       --save-space
              work slower, but using less space

   Archive filters
       -P PREFIX, --prefix PREFIX
              only consider archive names starting with this prefix.

       -a GLOB, --glob-archives GLOB
              only consider archive names matching the glob. sh: rules apply, see "borg help patterns". --prefix
              and --glob-archives are mutually exclusive.

       --sort-by KEYS
              Comma-separated list of sorting keys; valid keys are: timestamp, name, id; default is: timestamp

       --first N
              consider first N archives after other filters were applied

       --last N
              consider last N archives after other filters were applied

SEE ALSO

       borg-common(1)

AUTHOR

       The Borg Collective

                                                   2020-12-24                                      BORG-CHECK(1)