Borg 2.0.0b22.dev612
borg prune¶
borg [common options] prune [options] [NAME]
positional arguments |
||
|
specify the archive name |
|
options |
||
|
do not change the repository |
|
|
output a verbose list of archives it keeps/prunes |
|
|
use a less wide archive part format |
|
|
output verbose list of archives it prunes |
|
|
output verbose list of archives it keeps |
|
|
specify format for the archive part (default: “{archive:<36} {time} [{id}]”) |
|
|
Format output as JSON. The form of |
|
|
keep all archives within this time interval |
|
|
number of secondly archives to keep |
|
|
number of minutely archives to keep |
|
|
number of hourly archives to keep |
|
|
number of daily archives to keep |
|
|
number of weekly archives to keep |
|
|
number of monthly archives to keep |
|
|
number of quarterly archives to keep (13 week strategy) |
|
|
number of quarterly archives to keep (3 month strategy) |
|
|
number of yearly archives to keep |
|
Archive filters — Archive filters can be applied to repository targets. |
||
|
only consider archives matching all patterns. See “borg help match-archives”. |
|
|
consider archives between the oldest archive’s timestamp and (oldest + TIMESPAN), e.g., 7d or 12m. |
|
|
consider archives between the newest archive’s timestamp and (newest - TIMESPAN), e.g., 7d or 12m. |
|
|
consider archives older than (now - TIMESPAN), e.g., 7d or 12m. |
|
|
consider archives newer than (now - TIMESPAN), e.g., 7d or 12m. |
|
Description¶
The prune command prunes a repository by soft-deleting all archives not matching any of the specified retention options.
Important:
The prune command will only mark archives for deletion (“soft-deletion”), repository disk space is not freed until you run
borg compact.You can use
borg undeleteto undelete archives, but only until you runborg 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.
The recommended way to use prune is to give the archive series name to it via the NAME argument (assuming you have the same name for all archives in a series). Alternatively, you can also use --match-archives (-a), then only archives that match the pattern 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 globs.
If you have multiple series of archives with different data sets (e.g. from different machines) in one shared repository, use one prune call per series.
The --keep-within option takes an argument of the form “<int><char>”,
where char is “y”, “m”, “w”, “d”, “H”, “M”, or “S”. For example,
--keep-within 2d means to keep all archives that were created within
the past 2 days. “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 of the system where borg prune runs, and weeks go from Monday to Sunday.
Specifying a negative number of archives to keep means that there is no limit.
Borg will retain the oldest archive if any of the secondly, minutely, hourly, daily, weekly, monthly, quarterly, 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-13weekly and --keep-3monthly rules are two different
strategies for keeping archives every quarter year.
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).
You can influence how the --list output is formatted by using the --short
option (less wide output) or by giving a custom format using --format (see
the borg repo-list description for more details about the format string).
Examples¶
Be careful: prune is a potentially dangerous command that removes backup archives.
By default, prune applies to all archives in the repository unless you restrict its operation to a subset of the archives.
The recommended way to name archives (with borg create) is to use the
identical archive name within a series of archives. Then you can simply give
that name to prune as well, so it operates only on that series of archives.
Alternatively, you can use -a/--match-archives to match archive names
and select a subset of them.
When using -a, be careful to choose a good pattern — for example, 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.
Do not forget to run borg compact -v after prune to actually free disk space.
The --keep-* options accept either a count (e.g. --keep-daily 7) or
a time interval (e.g. --keep-daily 7d). A count keeps up to N archives
per period (e.g. the last 7 daily archives), while an interval keeps one
archive per period within that time span (e.g. one daily archive per day in the
last 7-day window). When using intervals, you may also specify --from to
set the reference timestamp for interval calculation.
# 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
# Similar to the above, but only apply to the archive series named '{hostname}':
$ borg prune -v --list --keep-daily=7 --keep-weekly=4 '{hostname}'
# Similar to the above, but 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 -a 'sh:{hostname}-*'
# 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
# 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=10d --keep-weekly=4 --keep-monthly=-1
# Keep daily archives from the last 7 days:
$ borg prune -v --list --dry-run --keep-daily=7d
# Same as above, but with a fixed reference timestamp:
$ borg prune -v --list --dry-run --from 2025-12-01T00:00:00+02:00 --keep-daily=7d
# Keep the last 14 archives using `--keep`:
$ borg prune -v --list --dry-run --keep 14
# Keep all archives from the last 30 days using `--keep`:
$ borg prune -v --list --dry-run --keep 30d
There are also visualized prune examples in docs/misc/prune-example.txt and
docs/misc/prune-example-interval.txt:
borg prune visualized
=====================
Assume it is 2016-01-01. Today's archive has not yet been made. You have
created at least one archive on each day in 2015 except on 2015-12-19 (no
backup was made on that day), and you started backing up with Borg on
2015-01-01.
This is what borg prune --keep-daily 14 --keep-monthly 6 --keep-yearly 1
would keep.
Archives kept by the --keep-daily rule are marked by a "d" to the right,
archives kept by the --keep-monthly rule are marked by a "m" to the right, and
archives kept by the --keep-yearly rule are marked by a "y" to the right.
Calendar view
-------------
2015
January February March
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1y 2 3 4 1 1
5 6 7 8 9 10 11 2 3 4 5 6 7 8 2 3 4 5 6 7 8
12 13 14 15 16 17 18 9 10 11 12 13 14 15 9 10 11 12 13 14 15
19 20 21 22 23 24 25 16 17 18 19 20 21 22 16 17 18 19 20 21 22
26 27 28 29 30 31 23 24 25 26 27 28 23 24 25 26 27 28 29
30 31
April May June
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 1 2 3 1 2 3 4 5 6 7
6 7 8 9 10 11 12 4 5 6 7 8 9 10 8 9 10 11 12 13 14
13 14 15 16 17 18 19 11 12 13 14 15 16 17 15 16 17 18 19 20 21
20 21 22 23 24 25 26 18 19 20 21 22 23 24 22 23 24 25 26 27 28
27 28 29 30 25 26 27 28 29 30 31 29 30m
July August September
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 1 2 1 2 3 4 5 6
6 7 8 9 10 11 12 3 4 5 6 7 8 9 7 8 9 10 11 12 13
13 14 15 16 17 18 19 10 11 12 13 14 15 16 14 15 16 17 18 19 20
20 21 22 23 24 25 26 17 18 19 20 21 22 23 21 22 23 24 25 26 27
27 28 29 30 31m 24 25 26 27 28 29 30 28 29 30m
31m
October November December
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 1 1 2 3 4 5 6
5 6 7 8 9 10 11 2 3 4 5 6 7 8 7 8 9 10 11 12 13
12 13 14 15 16 17 18 9 10 11 12 13 14 15 14 15 16 17d18d19 20d
19 20 21 22 23 24 25 16 17 18 19 20 21 22 21d22d23d24d25d26d27d
26 27 28 29 30 31m 23 24 25 26 27 28 29 28d29d30d31d
30m
List view
---------
--keep-daily 14 --keep-monthly 6 --keep-yearly 1
----------------------------------------------------------------
1. 2015-12-31 (2015-12-31 kept (2015-12-31 kept
2. 2015-12-30 by daily rule) by daily rule)
3. 2015-12-29 1. 2015-11-30 1. 2015-01-01 (oldest)
4. 2015-12-28 2. 2015-10-31
5. 2015-12-27 3. 2015-09-30
6. 2015-12-26 4. 2015-08-31
7. 2015-12-25 5. 2015-07-31
8. 2015-12-24 6. 2015-06-30
9. 2015-12-23
10. 2015-12-22
11. 2015-12-21
12. 2015-12-20
(no archive made on 2015-12-19)
13. 2015-12-18
14. 2015-12-17
Notes
-----
2015-12-31 is kept due to the --keep-daily 14 rule (because it is applied
first), not due to the --keep-monthly or --keep-yearly rule.
Rules are applied in the order given: archives already kept by an earlier
rule are excluded from consideration by later rules.
The --keep-yearly 1 rule does not consider the December 31st archive because it
has already been kept due to the daily rule. There are no archives from
previous years, so there are no "true" yearly candidates. The oldest archive at
2015-01-01 fills the remaining slot and will be kept until the rolling backup
scheme reaches "steady state" (when all retention rules are fully satisfied).
The --keep-monthly 6 rule keeps Nov, Oct, Sep, Aug, Jul and Jun. December is
not considered for this rule, because that archive was already kept because of
the daily rule.
2015-12-17 is kept to satisfy the --keep-daily 14 rule, because no archive was
made on 2015-12-19. If an archive had been made on that day, it would not keep
the archive from 2015-12-17.
We did not include weekly, hourly, minutely, or secondly rules to keep this
example simple. They all work in basically the same way.
The weekly rule is easy to understand roughly, but hard to understand in all
details. If you are interested, read "ISO 8601:2000 standard week-based year".
The 13weekly and 3monthly rules are two different strategies for keeping one
archive every quarter of a year. There are `multiple ways` to define a
quarter-year; borg prune recognizes two:
* --keep-13weekly keeps one archive every 13 weeks using ISO 8601:2000's
definition of the week-based year. January 4th is always included in the
first week of a year, and January 1st to 3rd may be in week 52 or 53 of the
previous year. Week 53 is also in the fourth quarter of the year.
* --keep-3monthly keeps one archive every 3 months. January 1st to March 31,
April 1st to June 30th, July 1st to September 30th, and October 1st to
December 31st form the quarters.
If the subtleties of the definition of a quarter-year don't matter to you, a
short summary of behavior is:
* --keep-13weekly favors keeping archives at the beginning of Jan, Apr, Jul,
and Oct.
* --keep-3monthly favors keeping archives at the end of Dec, Mar, Jun, and Sep.
* Both strategies will have some overlap in which archives are kept.
* The differences are negligible unless archives considered for deletion were
created weekly or more frequently.
.. _multiple ways: https://en.wikipedia.org/wiki/Calendar_year#Quarter_year
borg prune visualized (count and interval mixed)
================================================================================
Scenario: You use borg to perform daily backups. As backups age, the day-to-day
changes become less important, so to save storage space you want older archives
to "thin out" over time while retaining most recent archives. Your backup
script runs `borg create`, immediately followed by `borg prune`.
Assume today is 2026-06-04 and you always start your backups at 16:00. You have
been creating backup archives starting at 16:00, followed by pruning, on most
days going back to late 2025. Today, `borg create` took a little longer than
usual. It's 16:12 now and you run `borg prune`.
You want Borg to keep one archive per day for one week, four weekly archives,
one archive per month for five months, and two yearly backups. For that, you
use the following command:
```
borg prune \
--keep-daily 1w \
--keep-weekly 4 \
--keep-monthly 5m \
--keep-yearly 2 \
--from '2026-06-04 16:00'
```
The `--keep-*` options reflect the intended retention policy exactly. Note the
different wording in the retention policy for weekly and yearly archives: They
aren't *interval*-based, but *count*-based.
Another important detail here is `--from`. Without it, intervals would be
calculated relative to the actual start time of `prune` - in this case 16:12.
Since your backups are always created at 16:00, this 12-minute shift would move
the cutoff point of intervals and could cause archives near the boundary to
unexpectedly fall outside the expected time window.
By specifying `--from '2026-06-04 16:00'`, all intervals are anchored to the
intended reference time (16:00), not the moment `prune` happens to run. This
ensures stable and predictable retention behavior, independent of when `prune`
actually runs.
The first archive was made on 2025-11-15. You missed the backups on 2026-03-31,
2026-05-24, and 2026-06-03.
Below you find an overview of what archives `prune` will keep.
Archives kept by the `--keep-daily` rule are marked by a "d" to the right,
archives kept by the `--keep-weekly` rule are marked by a "w" to the right,
archives kept by the `--keep-monthly` rule are marked by a "m" to the right,
archives kept by the `--keep-yearly` rule are marked by a "y" to the right, and
archives kept by the `--from` rule are marked by a "x" to the right.
Calendar view
-------------
2025
November December
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15y16 15 16 17 18 19 20 21
17 18 19 20 21 22 23 22 23 24 25 26 27 28
24 25 26 27 28 29 30 29 30 31m
2026
January February March
1 2 3 4 1 1
5 6 7 8 9 10 11 2 3 4 5 6 7 8 2 3 4 5 6 7 8
12 13 14 15 16 17 18 9 10 11 12 13 14 15 9 10 11 12 13 14 15
19 20 21 22 23 24 25 16 17 18 19 20 21 22 16 17 18 19 20 21 22
26 27 28 29 30 31m 23 24 25 26 27 28m 23 24 25 26 27 28 29
30m31
April May June
1 2 3 4 5 1 2 3w 1d 2d 3 4x
6 7 8 9 10 11 12 4 5 6 7 8 9 10w
13 14 15 16 17 18 19 11 12 13 14 15 16 17w
20 21 22 23 24 25 26 18 19 20 21 22 23w24
27 28 29 30m 25 26 27 28d29d30d31d
List view
---------
--keep-daily 1w --keep-weekly 4 --keep-monthly 5m --keep-yearly 2
--------------------------------------------------------------------------------
1. 2025-11-15 (oldest)
1. 2026-06-02 1. 2026-05-23 1. 2026-04-30
2. 2026-06-01 2. 2026-05-17 2. 2026-03-30
3. 2026-05-31 3. 2026-05-10 3. 2026-02-28
4. 2026-05-30 4. 2026-05-03 4. 2026-01-31
5. 2026-05-29 5. 2025-12-31
6. 2026-05-28
2026-06-04 is additionally kept due to `--from`.
Notes
-----
The current day's archive is always kept, because `create` ran after the date
given with `--from`. For `prune`, it's as if this archive doesn't exist (yet).
2026-06-03 was skipped, so no archive can be kept with `--keep-daily` for that
day. Other than with a *count*-based policy, no compensation is made for an
*interval* like `--keep-daily 1w`, so the rule simply keeps one archive fewer.
2026-05-28 16:00 is exactly one week before `--from`. Since `create` always
runs after 16:00, the archive created on 2026-05-28 is kept, too. Without
`--from`, Borg would cut off at 2026-05-28 16:12 instead, which would likely
mean that the archive created on 2026-05-28 would be pruned. `--from` ensures
that 2026-05-28 is consistently kept. If you want it consistently pruned, try a
later reference time, e.g. `--from '2026-06-04 23:59:59'`.
2026-05-31 is considered not only by `--keep-daily`, but by `--keep-weekly`
and `--keep-monthly`, too. The archive is effectively kept by `--keep-daily`,
but how this affects other rules differs between *count*- and *interval*-based
policies. For *interval*-based rules like `--keep-monthly 5m` it has no effect:
The rule simply keeps one archive fewer in that case.
For *count*-based rules like `--keep-weekly 4` it has an effect: The policy
tells Borg to keep 4 weekly archives. Weekly slots are identified by ISO week
number; in this example the four kept archives cover weeks 18 through 21. If
2026-05-31 is kept by another rule already, Borg compensates by keeping an
older archive instead. Consequently, Borg will also keep the 2026-05-03 archive.
The week 22 slot is consumed by that same 2026-05-31 archive. Any other
archive from that week is not kept by weekly, even if it falls within the
daily window boundary. This is why 2026-05-27 is pruned: it has just fallen
out of the daily window, and no other rule covers it.
Since 2026-05-24 and 2026-03-31 were skipped, Borg substitutes the next best
candidate for each: 2026-05-23 fills the week 21 weekly slot, and 2026-03-30
fills the March monthly slot.
The implementation of `--keep-monthly 5m` is somewhat special: Borg defines a
month as a fixed 31-day period, independent of the actual calendar dates
involved. As a result, `5m` corresponds to 5 × 31 = 155 days. The archive from
2025-12-31 16:00 is exactly 155 days older than the reference time and is
therefore retained by `--keep-monthly`.
As a result, there are no true yearly candidates. In the absence of a better
candidate, `--keep-yearly 2` only matches the oldest archive, 2025-11-15.
Since interval rules define time windows rather than competing for a fixed
number of slots, their interplay is simpler than count-based rules. An archive
is kept by an interval rule as long as it falls within the specified window;
the next rule simply considers whatever remains.
Intervals and counts can be mixed freely. Yearly retention in this example is
done by retention count instead of intervals. A count rule paired with interval
rules behaves just as it would if all preceding rules were also counts:
Archives already kept by earlier rules are excluded from consideration. In this
example, every yearly slot is consumed by earlier rules; no true yearly
candidate remains, so the oldest archive at 2025-11-15 is kept to preserve
rolling backup semantics.