borg-check - Check repository consistency
borg [common options] check [options] [REPOSITORY_OR_ARCHIVE]
The check command verifies the consistency of a repository and the
corresponding archives.
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.
- If we are in repair mode and a integrity error is detected for a segment,
we try to recover as many objects from the segment as possible.
- In repair mode, it makes sure that the index is consistent with the data
stored in the segments.
- If you use a remote repo server via ssh:, the repo check is executed on
the repo 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. If a chunk is not present and we are in
repair mode, replace it with a same-size replacement chunk of zeros. If a
previously lost chunk reappears (e.g. via a later backup) and we are 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.
- If we are in repair mode and we checked all the archives: delete orphaned
chunks from the repo.
- if you use a remote repo server via ssh:, the archive check is executed on
the client machine (because if encryption is enabled, the checks will
require decryption and this is always done client-side, because key access
will be required).
- 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.
See borg-common(1) for common options of Borg commands.
- -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