When upgrading from Ubuntu 12.04 to 14.04 there is the possibility that you will encounter an error with the GRUB installation which can result in the system not booting properly. To prevent this, we recommend to configure the GRUB Package beforehand with the following command:
This command allows GRUB to remember the devices it manages.
With the following command you can check if the reconfiguration worked:
debconf-show grub-pc | grep install_devices
The reconfiguration worked when the following appears:
* grub-pc/install_devices: /dev/vda
As you can see, it is able to list the installed devices and therefore survives an upgrade. The upgrade can now be run using the following command: