Comment 54 for bug 1889509

I'm unable to fix this on my ubuntu 16 machine.

# debconf-get-selections | grep -E 'grub-(efi|pc)/install_devices[^_]'
grub-pc grub-pc/install_devices multiselect /dev/xvda1

# debconf-set-selections
grub-pc grub-pc/install_devices multiselect /dev/vda1
grub-pc grub-pc/install_devices_disks_changed multiselect /dev/vda1

# dpkg-reconfigure grub-pc
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.4.0-186-generic
Found initrd image: /boot/initrd.img-4.4.0-186-generic
Found linux image: /boot/vmlinuz-4.4.0-185-generic
Found initrd image: /boot/initrd.img-4.4.0-185-generic
Found linux image: /boot/vmlinuz-4.4.0-184-generic
Found initrd image: /boot/initrd.img-4.4.0-184-generic
done

When i reboot i get the default grub> prompt, and can boot by typing the correct commands from:
https://www.linux.com/training-tutorials/how-rescue-non-booting-grub-2-linux/