[Users] Basic questions about ploop snapshotting

[Scott Dowdle]

Greetings,

I haven't used filesystem snapshot'ing before and really like ploop and the fact that it has snapshot features.  I do have some basic questions because of this inexperience.  Hopefully people can help educate me on this topic.

So, I have a container that doesn't currently have a snapshot... but I'm wanting to do something potentially dangerous (say a Zimbra upgrade) and I want to be able to easily rollback if the upgrade fails.  That is a very common case.  So first I make a snapshot.  let's say I'm on Zimbra 8.0.6 and want to update to 8.0.8.  Before I do the upgrade, I want to make a snapshot.  So I do something like:

vzctl snapshot {ctid} --name zimbra806 --skip-suspend --skip-config

A snapshot is created and I can see it with "vzctl snapshot-list {ctid}"

What that really does it take the existing root.hdd and make it read only, and then create an additional image that stores all new writes.  This new image is called the delta... and the container is currently using it.

So let's pretend I do the Zimbra upgrade and if fails... and I want to throw away the delta.. and get back to the state of my container before I made those changes.

If I do a "vzctl snapshot-delete {ctid} --id {uuid}" that basically merges the changes in the delta down to the read-only image, removes the delta... and the changes are permanent now.  That is definitely NOT what I want.

So how do I do what I want?  How do I say, throw away the delta... and give me back my container before the changes?

I think I'm having some brainfart moment on how snapshots really function.

Thanks in advance,
-- 
Scott Dowdle
704 Church Street
Belgrade, MT 59714
(406)388-0827 [home]
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