Confirming for Ubuntu beta any my external usb drive (internal one disabled for testing)
# grub-install --debug --force /dev/sda ... + /usr/sbin/grub-probe --device-map=/boot/grub/device.map --target=device /boot/grub /usr/sbin/grub-probe: error: cannot stat `aufs'. + grub_device= + exit 1
Confirming for Ubuntu beta any my external usb drive (internal one disabled for testing)
# grub-install --debug --force /dev/sda grub-probe --device- map=/boot/ grub/device. map --target=device /boot/grub grub-probe: error: cannot stat `aufs'.
...
+ /usr/sbin/
/usr/sbin/
+ grub_device=
+ exit 1