how to use external snapshots with memory state

[Riccardo Ravaioli]

Hi all,

Can I get some feedback on these two questions I posted a while back,
concerning external snapshots:

 On Tue, 26 Jan 2021 at 00:15, Riccardo Ravaioli <riccardoravaioli at gmail.com>
wrote:
[...]

> 1) When creating an external online snapshot (disks+memory) of a qemu-KVM
> VM, I'd like to store the backing files in a separate folder and rename the
> newly-created delta files with the respective names of the original disks
> (now the backing files). Is this possible at all? Say a VM has a disk
> vm/disk1.qcow2 and I take an external snapshot, I'd like the backing file
> to appear in snap/disk1.qcow2 and the new delta disk to appear as
> vm/disk1.qcow2. Currently I wait for the VM to be shutdown by the user
> before I move around disks as desired and run qemu-img rebase in unsafe
> mode to update the delta disks. Can I accomplish the same result while the
> VNF is running?
>
> 2) As you suggested, I now use "virsh restore" to launch a VM with the
> memory state I had previously backed up. The "virsh restore" API applies to
> a VM that is not running. However, I see that for internal snapshots,
> libvirt also supports a snapshot-revert operation on a /live/ VM. Is this
> possible at all with an external snapshot? If so, what are the commands
> needed? My current way of automating a snapshot-revert with an external
> online snapshot only applies to a shutdown VM. It consists in:
> - shutting down the VM;
> - erasing all its delta disks, replacing them with new ones;
> - executing "virsh restore" on the memory state, making sure that the disk
> paths referenced in the embedded XML file are correct.
> Does this seem reasonable? Can I do the same while the VNF is running?
> I suppose that for a snapshot-delete operation on a live VM I just need to
> run "virsh blockpull" on each disk, but I couldn't figure out how to do a
> revert.
>


Thanks a lot!

Riccardo
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