Question about zfs snapshots and clones

David Demelier demelier.david at
Wed Jan 29 08:04:36 UTC 2014

Hello there,

I have a question about snapshots and clones. I created a template
dataset and snapshot for creating new jails. I call it
tank/jails/template and tank/jails/template at 1.

So we have:

tank/jails/template at 1
tank/jails/A (origin template at 1)
tank/jails/B (origin template at 1)

Now, I wanted to upgrade the template and create a new snapshot @2. Then
I would like to destroy the @1 because it will not be used to create new
jails. Because it's the parent of A and B I needed to promote them and
there is the thing that I didn't understand. I thought that promote was
a way to `detach' the children of a parent so that jails lives on their
own but it's not actually what I expected.

zfs promote on tank/jails/A and tank/jails/B gave me unexpected results.
I got my tank/jails/template at 1 renamed to something like tank/jails/B at 1
and the origin of tank/jails/A has been set to the latest IIRC.

So, I'm guessing that promote is not actually what I wanted, how should
I release the jails origin so they are completely free and I can destroy
the oldest template snapshot?


David Demelier

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