Comment 86 for bug 1289977

@Mathias #85 actually we've had grub2 for a long time (since 13.04 I think)...
Anyway, either "Release Upgrader" or "Grub2" can induce this problem.

I don't have that grub-pc package which Phillip mentioned all the time. My machine is on efi.
Everything works smoothly until doing this upgrade from saucy to "trusty"...
But it's lucky that my machine has a efi setup rather than bios/grub-pc. So when I see this grub error on starup, I can still boot by restarting the computer and choosing to boot from UEFI file. When I booted into the system, I tried to fix this problem by a manually grub-install (of course to the correct device). The "grub-install" command said finished and no error. But it didn't work at all. The problem still existed. Then a simple downgrade of grub-* packages solve the problem. This time "grub-install" printed out more information (as I pointed out at #58, the BootOrder and boot items ) besides just saying finished.

so where the problem is...