ZFS delete snapshots with interdependencies and clones

zfs

Below is my list of ZFS volumes and snapshots, as well as the origin and clone for each.

I want to delete all the snapshots, but keep all the filesystems. How can I do this?

I have tried zfs promote followed by attempting to delete each filesystem for many different combinations of the filesystems. This shifts around where the snapshots "live"; for instance, zfs promote tank/containers/six moves snapshot F from tank/containers/three@F to tank/containers/six@F. The live data in the filesystem isn't modified (which is what I want!), but I still can't delete the snapshot (which is not what I want).

A typical zfs destroy attempt tells me it has dependent clones, some of which (the snapshots) I do want to destroy, but others of which (the filesystems) I do not want to destroy.

For example.

# zfs destroy tank/containers/six@A
cannot destroy 'tank/containers/six@A': snapshot has dependent clones
use '-R' to destroy the following datasets:
tank/containers/five
tank/containers/two@B
tank/containers/two

In the above example, I don't want to destroy tank/containers/five or tank/containers/two, but if I zfs promote five and two, I still can't destroy any snapshots. Is there a solution?

# zfs list -t all -o name,origin,clones
NAME                         ORIGIN                       CLONES
tank                         -                            -
tank/containers              -                            -
tank/containers/five         tank/containers/two@B        -
tank/containers/four         tank/containers/six@C        -
tank/containers/one          -                            -
tank/containers/one@E        -                            tank/containers/three
tank/containers/two          tank/containers/six@A        -
tank/containers/two@B        -                            tank/containers/five
tank/containers/six          tank/containers/three@F      -
tank/containers/six@A        -                            tank/containers/two
tank/containers/six@C        -                            tank/containers/four
tank/containers/three        tank/containers/one@E        -
tank/containers/three@F      -                            tank/containers/six

Best Answer

AFAIK you're going to have to copy those datasets out to new, independent datasets. Promotion just switches around which dataset is "parent" vs "child", it doesn't actually break any dependencies if you want to keep both.

Eg: 

root@box~# zfs snapshot tank/containers/six@1 
root@box~# zfs send tank/containers/six@1 | pv | zfs receive tank/containers/newsix  
root@box~# zfs destroy -R tank/containers/six  
root@box~# zfs destroy tank/containers/three@F 
root@box~# zfs rename tank/containers/newsix tank/containers/six

Take your time and be sure of what you're doing. Especially with the actual deletions.

This replication is block-for-block, so if there's any significant data in there it WILL take a while. The pv part is strictly optional, but will give you a progress bar to look at while you wait.

Also maybe consider syncoid to automate the replication tasks, now and in the future. (Obligatory: I am the original author of this tool, which is GPLv3 licensed and free to use.)

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