borg [common options] compact [options]
Free repository space by deleting unused chunks.
borg compact analyzes all existing archives to find out which chunks are actually used. There might be unused chunks resulting from borg delete or prune, which can be removed to free space in the repository.
Differently than borg 1.x, borg2’s compact needs the borg key if the repo is encrypted.
# compact segments and free repo disk space
$ borg compact