Retention

retention:
  keep-last: 30
  keep-daily: 7
  keep-weekly: 4
  keep-monthly: 12

Snapshots are pruned after every successful backup according to the policy, and backupd prune <plan> applies the policy on demand (--dry-run reports what would be deleted without deleting anything). All four policies can be combined; a snapshot is kept if any policy keeps it.

Policies

Field	Description
keep-last	Always keep the N most recent snapshots
keep-daily	Keep N snapshots, one per day (most recent of each day)
keep-weekly	Keep N snapshots, one per week (most recent of each ISO week)
keep-monthly	Keep N snapshots, one per month (most recent of each month)

Example - with the config above, backupd keeps:

• the 30 newest snapshots,
• plus the newest snapshot of each of the last 7 days,
• plus the newest snapshot of each of the last 4 weeks,
• plus the newest snapshot of each of the last 12 months.

Older snapshots and their objects are removed from the bucket. Deduplication blocks that are no longer referenced by any remaining snapshot are garbage-collected in the same pass; plans without a retention policy still get orphaned blocks collected after every successful run and after failed runs.

Note

keep-last is the only policy that guarantees N snapshots exist. The calendar-based policies only prune when there is a newer snapshot in the same period.