So, today we had a customer that was using a custom VHD/VDI with his server and it wasn’t working. I knew it would be one of the 3 things:

1) incorrect vm_mode flag
2) Image size too big for flavors ‘min disk’
3) image using journaling

As it turned out this customer was using journaling. However, if it was a PV HVM type, here is how I would correctly set the mode

supernova customer image-meta vfd09a81-g431-4279-9467-5e4284944b53 set vm_mode=hvm

Pretty simple fix.