Re: Booting 64-bit Linux on a Macbook5,2

[Colin Watson]

On Wed, Sep 22, 2010 at 03:16:24PM -0400, Patrick Doyle wrote:
> I don't know where to turn here.  It seems that every thread I've
> found that describes this ends with "and now it works", but I can't
> seem to get there.
> 
> I have installed 64-bit Ubuntu 10.04 on a Macbook5,2.  I would like to
> boot this without the acpi=off parameter that is currently required.
> Once, in the past, I installed grub-efi in the /efi folder and was
> able to boot a 32-bit Ubuntu installation on this hardware.  But I
> have since installed the 64-bit version and can no longer get it to
> boot.  It gets as far as displaying the message about loading initrd
> and stops there.

Unlike on BIOS systems, on EFI systems the bit length of the kernel must
match the bit length of the firmware (at least on Linux; Vladimir tells
me that the XNU kernel in Darwin does some horrible things to work
around this restriction).  Thus there are two possibilities:

  1) You have 32-bit EFI, and won't be able to boot a 64-bit kernel from
     it.

  2) You have 64-bit EFI, and your previous 32-bit kernel was actually
     silently falling back to BIOS compatibility mode.

In either case, I'd recommend trying an ordinary BIOS version of GRUB
instead (i.e. the grub-pc package); you'll need to create a BIOS Boot
Partition (http://grub.enbug.org/BIOS_Boot_Partition), install GRUB to
that partition rather than to the MBR, and tell rEFIt to boot from that
partition.

-- 
Colin Watson                                       address@hidden