[libvirt-users] Blockpull while domain is shutoff

[Peter Krempa]

On Wed, Jul 03, 2019 at 14:07:10 -0400, Roger Jin wrote:
> Hi Libvirt,
> Is there a command that performs the same operation as blockpull while a
> domain is shutoff?  I have a backing chain
> 
> base <-- A <-- B
> 
> that I would like to shorten to
> 
> base <-- B


Generally we refer as 'base' to the image which has overlays, so you are
here describing a 'commit' operation. Which image is the topmost overlay
used by the vm?

> It seems like blockpull B, setting --base <path-to-base> does this, but
> only when the domain is running.

Libvirt currently does not implement these operations while the VM is
shutoff because the difference of interactions beween qemu and qemu-img.

As a workaround, you can either do the pull via qemu-img manually, or
start the vm in paused mode (virsh start --paused), then do the
blockpull and then 'virsh destroy' the VM. The filesystems would be
never touched so 'destroy' should be safe in this case.
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