0.12.3 doesn't remove any snapshots if there is a zfs hold on one of them about znapzend HOT 5 OPEN

well, if snapshots are created by znapzend they should not be 'hold'.

in your specific setup where snaphots not created by znapzend exist, you might want to have a look at the so called 'oracleMode' feature which will exactly do what you are asking for: https://github.com/oetiker/znapzend/blob/master/doc/znapzend.pod

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What if one wants to temporarily avoid destruction of a particular snapshot ?

(And what if one wants to temporarily mount or clone a particular snapshot ?)

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@rottegift how about determining holds while scanning the snapshots and then excluding them from destruction ? would this be a worthy task for your first contribution ?

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Hello, I have the same issue with a zfs clone/promote on a volume : snapshot used is locked on purpose, and znapzend cannot delete it (happily !), but then snaps are accumulating on it.

For this exact matter, we can find locked snapshot by using "zfs get origin -r $zpoolname", or snaps with "zfs get clones" != ''

For snaps locked by "zfs hold", property 'userrefs' is incremented, so we need to check all snaps where property userrefs > 0.

I checked the value for a snapshot that is the origin of a clone, and userrefs = 0.
So we need to exclude snaps based on both properties : "zfs get clones,userrefs -r $zpoolName" to grab everything we need.

I will be happy to contribute on this, even if I'm not particularly fluent in Perl. Can you help me a bit and tell me where would it be nicer to add this check ?

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I would assume that the place where we get the list of existing snapshots would be the right place to get these attributes as well so that we are able to skip the 'special' snapshots ... lib/ZnapZend/ZFS.pm#L142

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