Comment 2 for bug 1491894

Louis Bouchard (louis) wrote :

Well, it looks like the culprit could pretty well be a wrong setting of the grub-pc/install_devices_empty variable.

Checking each context I find :

Lucid (initial) : grub-pc/install_devices_empty: true
Lucid (post reconf) : grub-pc/install_devices_empty: true

Whereas on a frech Precise install we have :
* grub-pc/install_devices: /dev/vda
   grub-pc/install_devices_empty: false

When upgrading from Lucid, the debconf values are wrong since even if grub has been installed, the debconf values do not reflect this so the first stage is not reinstalled, hence the failed boot.