[Users] Basic questions about ploop snapshotting

[Roman Haefeli]

Hi Scott

Without having fully read your second mail I think you want something
like this:

* You have CT with Zimbra 8.0.6 installed and you want to upgrade t
8.0.8

* You create a snapshot like this:
  $ vzctl snapshot CTID --name pre-upgrade-808

* You perform the upgrade and it goes havoc and you would like 
  restore the previous state.

* You do:
  $ vzctl snapshot-list CTID
  You copy the UUID of the snapshot with the name
  'pre-upgrade-808'

* You restore by doing:
  vzctl snapshot-switch CTID --id <paste-the-uuid-here>

By doing the last step, you lose the state of the CTID with the broken
upgrade. If you want to keep it for some reason, do another 'vzctl
snapshot CTID' before restoring.

Roman



On Don, 2014-10-16 at 14:02 -0600, Scott Dowdle wrote:
> 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.
> iu6h.iu
> 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,