[libvirt] [PATCH 1/2] snapshots: allow create --redefine to force a new configuration

[Richard Moore]

>
> On Wed, Mar 20, 2019 at 8:53 AM Peter Krempa <pkrempa redhat com>
> wrote:
>
> I'm not persuaded that this workaround is necessary.
>
> Thanks Peter for taking a deeper look!
>
> And yes your summary seems correct.
> I personally still like to give admins the ability to force configs,
> but I'm ok if the general upstream opinion to that is no.
>
> I have asked the reporter - on the bug that I got - to chime in here
> and
> do the "convincing" as he is the affected person I think he is more
> able
> to do so - e.g. express the pain with the suggested workaround.

>
> --
> Christian Ehrhardt
> Software Engineer, Ubuntu Server
> Canonical Ltd

Hi,

I am the original fix requestor who Christian has put up with for quite
some time now!

I will try and summarise in brief;

The initial problem was the machine type I had set in various
snapshots/VM's had been deprecated and thus rendered the snapshots all
unusable after upgrading O/S (that came packaged with newer
libvirt/qemu versions.)

I thus needed a simple, intuitive way to edit the snapshots to a
machine type that was still supported, permanently.
snapshot-edit seemed the appropriate tool for doing this, but alas it
would not, a way was needed to force it to save the changes.

One of my main reasons for using vm/snapshots is testing software
install behaviour/compatibility in Windows, so I have a variety of
Windows versions, each with snapshots taken with various levels of core
'things' installed (.net framework , C++ redistributables etc.)
Thus the snapshots could be many years old. I need to be able to flick
between them, so being able to permanently 'fix' them is my goal.

The second issue was similarly being able to edit other 'simple' facets
of the snapshots  e.g.

Attached disks, floppies or ISO's - or paths to them.
Memory, if testing something that needed more than I ever invisaged way
back when.
MAC address (we have to register devices on the network via MAC, which
expire, and can then render the snapshot unusable if I cannot change
the MAC in the snapshot)

I hope this makes sense, I have tried to be brief, I can elaborate
further if needed.

I think being able to edit existing snapshots simply, with once
command, would be very beneficial to many people.
(I think most people trying to do this would be aware of the risks,
especially if the alternative is that the snapshot doesn’t work
anyway.)

Cheers

Richard Moore