Re: GRUB2 (packaged with Ubuntu 12.10) won't boot OS X

[Jake Thomas]

I had this _same_exact_ problem yesterday. And once again, Chris
Murphy, you had the answer, so I thank you again.

As Mr. Murphy pointed out, the problem was caused by me having a
hybrid GPT/MBR setup. Simply changing it back to pure GPT fixed the
problem:

sudo gdisk /dev/sda

x //Enters the Expert menu

n //Creates a new protective MBR

w //Writes - actually does it


Now I can chainload Apple's boot.efi file just fine without the error
"not a valid root device".

The long, long, complex menuentry generated by grub-mkconfig to boot
Mac OS X still doesn't work.

What's weird is that I used to be able to chainload boot.efi with a
hybrid setup no problem. But after updating my Grub efi image (made
from Grub compiled from source from bzr a couple days ago), I got the
error.

Why would it no longer be able to load the efi image off a hybrid
disk? It makes no sense to me because it can still see and read the
file (ls command) off one.

Cheers,
Jake