[ovirt-users] manually merging thin provisioned Ovirt Images

[Adam Litke]

On 17/04/15 10:51 +0200, InterNetX - Juergen Gotteswinter wrote:
>Hi,
>
>accidently, i delete the wrong live snapshot of a Virtual Machine. Which
>whouldnt be that big deal, since Filer Snapshots are created every hour.
>
>But... after pulling out the qcow Files of the VM, i am confronted with
>several files.
>
>- the biggest one, which is most likely the main part from what i was
>able to investigate with qemu-img
>- several smaller files, which seem to contain the delta - so i expect
>this files be the live snaps of the vm
>
>could anyone  point me into a direction to:
>
>- push the restored main image file + snapshot files back into ovirt (if
>its hacky, ok..)
>
>or
>
>- how to find out which snapshot files need to be merged into the main
>qcow image to get the latest state
>
>for option 2, importing a single qcow image is imho no big deal
>(virt-v2v). but how the heck do i find out in which order / which files
>needs to be merged ?

If you already have the set of files and you're looking for the order,
you can use qemu-img info to determine the chain.

For each file in the set, run the following command:

    qemu-img info --backing-chain <file>

Repeat this until you find the volume which includes all of the others
in its backing chain output.  This volume is the leaf.  If you want to
easily produce a single, merged volume you can then use the qemu-img
convert command:

    qemu-img convert -O qcow2 <old-leaf> <new-file>

Hope this helps.

-- 
Adam Litke