borg compact

borg [common options] compact [options]

options

-n, --dry-run

do not change the repository

-s, --stats

print statistics (might be much slower)

Common options

Description

Free repository space by deleting unused chunks.

borg compact analyzes all existing archives to determine which repository objects are actually used (referenced). It then deletes all unused objects from the repository to free space.

Unused objects may result from:

  • use of borg delete or borg prune

  • interrupted backups (consider retrying the backup before running compact)

  • backups of source files that encountered an I/O error mid-transfer and were skipped

  • corruption of the repository (e.g., the archives directory lost entries; see notes below)

You usually do not want to run borg compact after every write operation, but either regularly (e.g., once a month, possibly together with borg check) or when disk space needs to be freed.

Important:

After compacting, it is no longer possible to use borg undelete to recover previously soft-deleted archives.

borg compact might also delete data from archives that were “lost” due to archives directory corruption. Such archives could potentially be restored with borg check --find-lost-archives [--repair], which is slow. You therefore might not want to do that unless there are signs of lost archives (e.g., when seeing fatal errors when creating backups or when archives are missing in borg repo-list).

When using the --stats option, borg will internally list all repository objects to determine their existence and stored size. It will build a fresh chunks index from that information and cache it in the repository. For some types of repositories, this might be very slow. It will tell you the sum of stored object sizes, before and after compaction.

Without --stats, borg will rely on the cached chunks index to determine existing object IDs (but there is no stored size information in the index, thus it cannot compute before/after compaction size statistics).

Examples

# Compact segments and free repository disk space
$ borg compact