borg-prune - Prune repository archives according to specified rules



borg-prune − Prune repository archives according to specified rules


borg [common options] prune [options] [REPOSITORY]


The prune command prunes a repository by deleting all archives not matching any of the specified retention options.

Important: Repository disk space is not freed until you run borg compact.

This command is normally used by automated backup scripts wanting to keep a certain number of historic backups. This retention policy is commonly referred to as GFS (Grandfather−father−son) backup rotation scheme.

Also, prune automatically removes checkpoint archives (incomplete archives left behind by interrupted backup runs) except if the checkpoint is the latest archive (and thus still needed). Checkpoint archives are not considered when comparing archive counts against the retention limits (−−keep−X).

If a prefix is set with −P, then only archives that start with the prefix are considered for deletion and only those archives count towards the totals specified by the rules. Otherwise, all archives in the repository are candidates for deletion! There is no automatic distinction between archives representing different contents. These need to be distinguished by specifying matching prefixes.

If you have multiple sequences of archives with different data sets (e.g. from different machines) in one shared repository, use one prune call per data set that matches only the respective archives using the −P option.

The −−keep−within option takes an argument of the form "<int><char>", where char is "H", "d", "w", "m", "y". For example, −−keep−within 2d means to keep all archives that were created within the past 48 hours. "1m" is taken to mean "31d". The archives kept with this option do not count towards the totals specified by any other options.

A good procedure is to thin out more and more the older your backups get. As an example, −−keep−daily 7 means to keep the latest backup on each day, up to 7 most recent days with backups (days without backups do not count). The rules are applied from secondly to yearly, and backups selected by previous rules do not count towards those of later rules. The time that each backup starts is used for pruning purposes. Dates and times are interpreted in the local timezone, and weeks go from Monday to Sunday. Specifying a negative number of archives to keep means that there is no limit. As of borg 1.2.0, borg will retain the oldest archive if any of the secondly, minutely, hourly, daily, weekly, monthly, or yearly rules was not otherwise able to meet its retention target. This enables the first chronological archive to continue aging until it is replaced by a newer archive that meets the retention criteria.

The −−keep−last N option is doing the same as −−keep−secondly N (and it will keep the last N archives under the assumption that you do not create more than one backup archive in the same second).

When using −−stats, you will get some statistics about how much data was deleted − the "Deleted data" deduplicated size there is most interesting as that is how much your repository will shrink. Please note that the "All archives" stats refer to the state after pruning.


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


repository to prune

optional arguments
, −−dry−run

do not change repository


force pruning of corrupted archives, use −−force −−force in case −−force does not work.

−s, −−stats

print statistics for the deleted archive


output verbose list of archives it keeps/prunes

−−keep−within INTERVAL

keep all archives within this time interval

−−keep−last, −−keep−secondly

number of secondly archives to keep


number of minutely archives to keep

−H, −−keep−hourly

number of hourly archives to keep

−d, −−keep−daily

number of daily archives to keep

−w, −−keep−weekly

number of weekly archives to keep

−m, −−keep−monthly

number of monthly archives to keep

−y, −−keep−yearly

number of yearly archives to keep


work slower, but using less space

−c SECONDS−−checkpoint−interval SECONDS

write checkpoint every SECONDS seconds (Default: 1800)

Archive filters

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.


Be careful, prune is a potentially dangerous command, it will remove backup archives.

The default of prune is to apply to all archives in the repository unless you restrict its operation to a subset of the archives using −−prefix. When using −−prefix, be careful to choose a good prefix − e.g. do not use a prefix "foo" if you do not also want to match "foobar".

It is strongly recommended to always run prune −v −−list −−dry−run ... first so you will see what it would do without it actually doing anything.

# Keep 7 end of day and 4 additional end of week archives.
# Do a dry−run without actually deleting anything.
$ borg prune −v −−list −−dry−run −−keep−daily=7 −−keep−weekly=4 /path/to/repo

# Same as above but only apply to archive names starting with the hostname
# of the machine followed by a "−" character:
$ borg prune −v −−list −−keep−daily=7 −−keep−weekly=4 −−prefix='{hostname}−' /path/to/repo
# actually free disk space:
$ borg compact /path/to/repo

# Keep 7 end of day, 4 additional end of week archives,
# and an end of month archive for every month:
$ borg prune −v −−list −−keep−daily=7 −−keep−weekly=4 −−keep−monthly=−1 /path/to/repo

# Keep all backups in the last 10 days, 4 additional end of week archives,
# and an end of month archive for every month:
$ borg prune −v −−list −−keep−within=10d −−keep−weekly=4 −−keep−monthly=−1 /path/to/repo

There is also a visualized prune example in docs/misc/prune−example.txt.


borg−common(1), borg−compact(1)


The Borg Collective

Updated 2023-02-15 - |