ZFS – How to Remove Files from Snapshots

zfs

Say I have a dataset with 100 snapshots and want to rm -rf all folders named "cache" in all snapshots.

I want to actually free up the space, not just hide it away in layers of snapshots, so making a clone and removing from that and then taking a new snapshot doesn't seem to do what I want.

Any semi-automatical way do that?
Some wrapping around zfs list -t snapshot, zfs clone, zfs promote, zfs snapshot?

(cross-posting from https://superuser.com/questions/313197 since I see this has more ZFS stuff)

Best Answer

Snapshots are read-only. If you need those folders gone then you have to delete the whole snapshot.

You can make a backup (with something like tar), excluding the offending folders, then delete the snapshot. Obviously the backup is now in tar, or whatever, format; but at least you still have a backup copy.

Related Solutions

How to Delete All but Last N ZFS Snapshots

You may find something like this a little simpler

zfs list -t snapshot -o name | grep ^tank@Auto | tac | tail -n +16 | xargs -n 1 zfs destroy -r

Output the list of the snapshot (names only) with zfs list -t snapshot -o name
Filter to keep only the ones that match tank@Auto with grep ^tank@Auto
Reverse the list (previously sorted from oldest to newest) with tac
Limit output to the 16th oldest result and following with tail -n +16
Then destroy with xargs -n 1 zfs destroy -vr

Deleting snapshots in reverse order is supposedly more efficient or sort in reverse order of creation.

zfs list -t snapshot -o name -S creation | grep ^tank@Auto | tail -n +16 | xargs -n 1 zfs destroy -vr

Test it with ...|xargs -n 1 echo.

ZFS: very big files + compression + snapshots

You should be using ZFS compression (with compression=lz4) by default these days. There's no good reason not to use it, except if you know that your data is not compressible.

Snapshots on compressed ZFS filesystems are still efficient and work with replication and/or rsync.

Best Answer

Related Solutions

How to Delete All but Last N ZFS Snapshots

ZFS: very big files + compression + snapshots

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