forked from TrueCloudLab/restic
c1a3de4a6e
Add a callback to the PruneOptions struct which calculates the number of
bytes allowed to be unused after prune is done. This way, the logic is
closer to the option parsing code.
Also, add an explicit option `unlimited` for the use case when storage
does not matter but bandwidth and time do. Internally, this sets the
maximum number of unused bytes to MaxUint64.
Rework the documentation slightly so that no more "packs" are
mentioned and it talks about "files" instead.
Make it clear in the documentation that the percentage given to
`--max-unused` is relative to the whole repository size after pruning is
done. If specified, it must be below 100%, otherwise the repository
would contain 100% of unused data, which is pointless.
I had a hard time coming up with the correct formula to calculate the
maximum number of unused bytes based on the number of used bytes. For a
fraction `p` (0 ≤ p < 1), a repo with `u` bytes used, and the number of
unused bytes `x` the following holds:
x ≤ p * (u+x)
⇔ x ≤ p*u + p*x
⇔ x - p*x ≤ p*u
⇔ x * (1-p) ≤ p*u
⇔ x ≤ p/(1-p) * u
363 lines
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ReStructuredText
363 lines
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ReStructuredText
..
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Normally, there are no heading levels assigned to certain characters as the structure is
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determined from the succession of headings. However, this convention is used in Python’s
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Style Guide for documenting which you may follow:
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# with overline, for parts
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* for chapters
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= for sections
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- for subsections
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^ for subsubsections
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" for paragraphs
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#########################
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Removing backup snapshots
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#########################
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All backup space is finite, so restic allows removing old snapshots.
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This can be done either manually (by specifying a snapshot ID to remove)
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or by using a policy that describes which snapshots to forget. For all
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remove operations, two commands need to be called in sequence:
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``forget`` to remove a snapshot and ``prune`` to actually remove the
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data that was referenced by the snapshot from the repository. This can
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be automated with the ``--prune`` option of the ``forget`` command,
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which runs ``prune`` automatically if snapshots have been removed.
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Pruning snapshots can be a time-consuming process, depending on the
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amount of snapshots and data to process. During a prune operation, the
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repository is locked and backups cannot be completed. Please plan your
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pruning so that there's time to complete it and it doesn't interfere with
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regular backup runs.
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It is advisable to run ``restic check`` after pruning, to make sure
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you are alerted, should the internal data structures of the repository
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be damaged.
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Remove a single snapshot
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************************
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The command ``snapshots`` can be used to list all snapshots in a
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repository like this:
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.. code-block:: console
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$ restic -r /srv/restic-repo snapshots
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enter password for repository:
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ID Date Host Tags Directory
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----------------------------------------------------------------------
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40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
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79766175 2015-05-08 21:40:19 kasimir /home/user/work
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bdbd3439 2015-05-08 21:45:17 luigi /home/art
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590c8fc8 2015-05-08 21:47:38 kazik /srv
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9f0bc19e 2015-05-08 21:46:11 luigi /srv
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In order to remove the snapshot of ``/home/art``, use the ``forget``
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command and specify the snapshot ID on the command line:
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.. code-block:: console
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$ restic -r /srv/restic-repo forget bdbd3439
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enter password for repository:
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removed snapshot d3f01f63
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Afterwards this snapshot is removed:
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.. code-block:: console
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$ restic -r /srv/restic-repo snapshots
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enter password for repository:
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ID Date Host Tags Directory
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----------------------------------------------------------------------
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40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
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79766175 2015-05-08 21:40:19 kasimir /home/user/work
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590c8fc8 2015-05-08 21:47:38 kazik /srv
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9f0bc19e 2015-05-08 21:46:11 luigi /srv
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But the data that was referenced by files in this snapshot is still
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stored in the repository. To cleanup unreferenced data, the ``prune``
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command must be run:
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.. code-block:: console
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$ restic -r /srv/restic-repo prune
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enter password for repository:
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repository 33002c5e opened successfully, password is correct
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loading all snapshots...
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loading indexes...
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finding data that is still in use for 4 snapshots
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[0:00] 100.00% 4 / 4 snapshots
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searching used packs...
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collecting packs for deletion and repacking
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[0:00] 100.00% 5 / 5 packs processed
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to repack: 69 blobs / 1.078 MiB
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this removes 67 blobs / 1.047 MiB
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to delete: 7 blobs / 25.726 KiB
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total prune: 74 blobs / 1.072 MiB
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remaining: 16 blobs / 38.003 KiB
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unused size after prune: 0 B (0.00% of remaining size)
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repacking packs
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[0:00] 100.00% 2 / 2 packs repacked
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counting files in repo
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[0:00] 100.00% 3 / 3 packs
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finding old index files
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saved new indexes as [59270b3a]
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remove 4 old index files
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[0:00] 100.00% 4 / 4 files deleted
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removing 3 old packs
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[0:00] 100.00% 3 / 3 files deleted
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done
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Afterwards the repository is smaller.
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You can automate this two-step process by using the ``--prune`` switch
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to ``forget``:
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.. code-block:: console
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$ restic forget --keep-last 1 --prune
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snapshots for host mopped, directories /home/user/work:
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keep 1 snapshots:
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ID Date Host Tags Directory
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----------------------------------------------------------------------
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4bba301e 2017-02-21 10:49:18 mopped /home/user/work
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remove 1 snapshots:
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ID Date Host Tags Directory
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----------------------------------------------------------------------
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8c02b94b 2017-02-21 10:48:33 mopped /home/user/work
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1 snapshots have been removed, running prune
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loading all snapshots...
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loading indexes...
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finding data that is still in use for 1 snapshots
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[0:00] 100.00% 1 / 1 snapshots
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searching used packs...
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collecting packs for deletion and repacking
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[0:00] 100.00% 5 / 5 packs processed
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to repack: 69 blobs / 1.078 MiB
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this removes 67 blobs / 1.047 MiB
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to delete: 7 blobs / 25.726 KiB
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total prune: 74 blobs / 1.072 MiB
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remaining: 16 blobs / 38.003 KiB
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unused size after prune: 0 B (0.00% of remaining size)
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repacking packs
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[0:00] 100.00% 2 / 2 packs repacked
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counting files in repo
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[0:00] 100.00% 3 / 3 packs
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finding old index files
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saved new indexes as [59270b3a]
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remove 4 old index files
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[0:00] 100.00% 4 / 4 files deleted
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removing 3 old packs
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[0:00] 100.00% 3 / 3 files deleted
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done
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Removing snapshots according to a policy
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****************************************
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Removing snapshots manually is tedious and error-prone, therefore restic
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allows specifying which snapshots should be removed automatically
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according to a policy. You can specify how many hourly, daily, weekly,
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monthly and yearly snapshots to keep, any other snapshots are removed.
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The most important command-line parameter here is ``--dry-run`` which
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instructs restic to not remove anything but print which snapshots would
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be removed.
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When ``forget`` is run with a policy, restic loads the list of all
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snapshots, then groups these by host name and list of directories. The grouping
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options can be set with ``--group-by``, to only group snapshots by paths and
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tags use ``--group-by paths,tags``. The policy is then applied to each group of
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snapshots separately. This is a safety feature.
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The ``forget`` command accepts the following parameters:
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- ``--keep-last n`` never delete the ``n`` last (most recent) snapshots
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- ``--keep-hourly n`` for the last ``n`` hours in which a snapshot was
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made, keep only the last snapshot for each hour.
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- ``--keep-daily n`` for the last ``n`` days which have one or more
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snapshots, only keep the last one for that day.
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- ``--keep-weekly n`` for the last ``n`` weeks which have one or more
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snapshots, only keep the last one for that week.
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- ``--keep-monthly n`` for the last ``n`` months which have one or more
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snapshots, only keep the last one for that month.
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- ``--keep-yearly n`` for the last ``n`` years which have one or more
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snapshots, only keep the last one for that year.
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- ``--keep-tag`` keep all snapshots which have all tags specified by
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this option (can be specified multiple times).
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- ``--keep-within duration`` keep all snapshots which have been made within
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the duration of the latest snapshot. ``duration`` needs to be a number of
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years, months, days, and hours, e.g. ``2y5m7d3h`` will keep all snapshots
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made in the two years, five months, seven days, and three hours before the
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latest snapshot.
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Multiple policies will be ORed together so as to be as inclusive as possible
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for keeping snapshots.
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Additionally, you can restrict removing snapshots to those which have a
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particular hostname with the ``--host`` parameter, or tags with the
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``--tag`` option. When multiple tags are specified, only the snapshots
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which have all the tags are considered. For example, the following command
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removes all but the latest snapshot of all snapshots that have the tag ``foo``:
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.. code-block:: console
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$ restic forget --tag foo --keep-last 1
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This command removes all but the last snapshot of all snapshots that have
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either the ``foo`` or ``bar`` tag set:
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.. code-block:: console
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$ restic forget --tag foo --tag bar --keep-last 1
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To only keep the last snapshot of all snapshots with both the tag ``foo`` and
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``bar`` set use:
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.. code-block:: console
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$ restic forget --tag foo,bar --keep-last 1
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All the ``--keep-*`` options above only count
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hours/days/weeks/months/years which have a snapshot, so those without a
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snapshot are ignored.
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For safety reasons, restic refuses to act on an "empty" policy. For example,
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if one were to specify ``--keep-last 0`` to forget *all* snapshots in the
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repository, restic will respond that no snapshots will be removed. To delete
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all snapshots, use ``--keep-last 1`` and then finally remove the last
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snapshot ID manually (by passing the ID to ``forget``).
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All snapshots are evaluated against all matching ``--keep-*`` counts. A
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single snapshot on 2017-09-30 (Sat) will count as a daily, weekly and monthly.
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Let's explain this with an example: Suppose you have only made a backup
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on each Sunday for 12 weeks:
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.. code-block:: console
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$ restic snapshots
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repository f00c6e2a opened successfully, password is correct
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ID Time Host Tags Paths
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---------------------------------------------------------------
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0a1f9759 2019-09-01 11:00:00 mopped /home/user/work
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46cfe4d5 2019-09-08 11:00:00 mopped /home/user/work
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f6b1f037 2019-09-15 11:00:00 mopped /home/user/work
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eb430a5d 2019-09-22 11:00:00 mopped /home/user/work
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8cf1cb9a 2019-09-29 11:00:00 mopped /home/user/work
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5d33b116 2019-10-06 11:00:00 mopped /home/user/work
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b9553125 2019-10-13 11:00:00 mopped /home/user/work
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e1a7b58b 2019-10-20 11:00:00 mopped /home/user/work
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8f8018c0 2019-10-27 11:00:00 mopped /home/user/work
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59403279 2019-11-03 11:00:00 mopped /home/user/work
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dfee9fb4 2019-11-10 11:00:00 mopped /home/user/work
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e1ae2f40 2019-11-17 11:00:00 mopped /home/user/work
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---------------------------------------------------------------
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12 snapshots
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Then ``forget --keep-daily 4`` will keep the last four snapshots for the last
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four Sundays, but remove the rest:
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.. code-block:: console
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$ restic forget --keep-daily 4 --dry-run
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repository f00c6e2a opened successfully, password is correct
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Applying Policy: keep the last 4 daily snapshots
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keep 4 snapshots:
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ID Time Host Tags Reasons Paths
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-------------------------------------------------------------------------------
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8f8018c0 2019-10-27 11:00:00 mopped daily snapshot /home/user/work
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59403279 2019-11-03 11:00:00 mopped daily snapshot /home/user/work
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dfee9fb4 2019-11-10 11:00:00 mopped daily snapshot /home/user/work
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e1ae2f40 2019-11-17 11:00:00 mopped daily snapshot /home/user/work
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-------------------------------------------------------------------------------
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4 snapshots
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remove 8 snapshots:
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ID Time Host Tags Paths
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---------------------------------------------------------------
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0a1f9759 2019-09-01 11:00:00 mopped /home/user/work
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46cfe4d5 2019-09-08 11:00:00 mopped /home/user/work
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f6b1f037 2019-09-15 11:00:00 mopped /home/user/work
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eb430a5d 2019-09-22 11:00:00 mopped /home/user/work
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8cf1cb9a 2019-09-29 11:00:00 mopped /home/user/work
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5d33b116 2019-10-06 11:00:00 mopped /home/user/work
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b9553125 2019-10-13 11:00:00 mopped /home/user/work
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e1a7b58b 2019-10-20 11:00:00 mopped /home/user/work
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---------------------------------------------------------------
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8 snapshots
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The result of the ``forget --keep-daily`` operation does not depend on when it
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is run, it will only count the days for which a snapshot exists. This is a
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safety feature: it prevents restic from removing snapshots when no new ones are
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created. Otherwise, running ``forget --keep-daily 4`` on a Friday (without any
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snapshot Monday to Thursday) would remove all snapshots!
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Another example: Suppose you make daily backups for 100 years. Then
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``forget --keep-daily 7 --keep-weekly 5 --keep-monthly 12 --keep-yearly 75``
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will keep the most recent 7 daily snapshots, then 4 (remember, 7 dailies
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already include a week!) last-day-of-the-weeks and 11 or 12
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last-day-of-the-months (11 or 12 depends if the 5 weeklies cross a month).
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And finally 75 last-day-of-the-year snapshots. All other snapshots are
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removed.
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Customize pruning
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*****************
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To understand the custom options, we first explain how the pruning process works:
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1. All snapshots and directories within snapshots are scanned to determine
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which data is still in use.
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2. For all files in the repository, restic finds out if the file is fully
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used, partly used or completely unused.
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3. Completely unused files are marked for deletion. Fully used files are kept.
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A partially used file is either kept or marked for repacking depending on user
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options.
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Note that for repacking, restic must download the file from the repository
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storage and re-upload the needed data in the repository. This can be very
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time-consuming for remote repositories.
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4. After deciding what to do, ``prune`` will actually perform the repack, modify
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the index according to the changes and delete the obsolete files.
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The ``prune`` command accepts the following options:
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- ``--max-unused limit`` allow unused data up to the specified limit within the repository.
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This allows restic to keep partly used files instead of repacking them.
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The limit can be specified in several ways:
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* As an absolute size (e.g. ``200M``). If you want to minimize the space
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used by your repository, pass ``0`` to this option.
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* As a size relative to the total repo size (e.g. ``10%``). This means that
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after prune, at most ``10%`` of the total data stored in the repo may be
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unused data. If the repo after prune has as size of 500MB, then at most
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50MB may be unused.
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* If the string ``unlimited`` is passed, there is no limit for partly
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unused files. This means that as long as some data is still used within
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a file stored in the repo, restic will just leave it there. Use this if
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you want to minimize the time and bandwidth used by the ``prune``
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operation.
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Restic tries to repack as little data as possible while still ensuring this
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limit for unused data.
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- ``--max-repack-size size`` if set limits the total size of files to repack.
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As ``prune`` first stores all repacked files and deletes the obsolete files at the end,
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this option might be handy if you expect many files to be repacked and fear to run low
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on storage.
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- ``--repack-cacheable-only`` if set to true only files which contain
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metadata and would be stored in the cache are repacked. Other pack files are
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not repacked if this option is set. This allows a very fast repacking
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using only cached data. It can, however, imply that the unused data in
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your repository exceeds the value given by ``--max-unused``.
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The default value is false.
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- ``--dry-run`` only show what ``prune`` would do.
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- ``--verbose`` increased verbosity shows additional statistics for ``prune``.
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