Where “deleting” a snapshot means forgetting it, followed by running prune. Or to put it another way, how much space is used by the data that is only referenced in one or more specified snapshots and nowhere else.
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Use restic forget <SNAP_ID(s)> --prune --dry-run. This tells you what prune would remove.
But note that prune doesn’t necessarily remove all data which is only referenced by those snapshots. By default, it tolerates some unused data.
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Awesome, thanks! There’s the --max-unused option that allows you to specify how much unused data it tolerates. If I set --max-unused 0 to your command above, am I correct in assuming that I will get the exact number I’m looking for?
Almost. You may have already unused data before you run this command. To check this, you could run restic prune --max-unused 0 --dry-run. If this tells, theres nothing to remove, than the forget` command will show exactly the number.
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