Re: EFI-dualbooting OSX and Linux on iMac with T7400-CPU

["Yoshinori K. Okuji" <okuji@enbug.org>]

On Sunday 03 December 2006 18:05, Eeri Kask wrote:
> After creating 4 partitions with MacOSX installation CD (and installing
> OSX) I installed Gentoo 2006.1 x86_64 onto the 4th partition (i.e.
> /dev/sda5; in OSX invisible FAT32 partition counts as /dev/sda1).
> Now I am kindly looking for help in making linux EFI-bootable using grub2.

Oh, great. :)

> Grub comes and gives lots of errors:
>
> (line 2-2)
> syntax error
> Incorrect command
> ...
> (line 12-12)
> Press any key to continue...

Hmm.. I think you need to put the open braces in the same line as "menuentry" 
commands.

> Then grub shows command line interface:
>
> grub> set root=(hd0,5)
> grub> linux /boot/vmlinuz root=/dev/sda5
> grub> boot
> grub> _
>
> is what I entered and now nothing happens.  However grub reads the
> ext3-formatted /dev/sda5 partition as typing TAB completes path- and
> filenames.

Please check the following:

- Make sure that the linux kernel is compiled with EFI support. I don't know 
how Gentoo defines the default settings, but most distributions do not enable 
it in default kernels, AFAIK.

- Make sure that the linux kernel has an appropriate video driver (or any 
other required drivers). Again, I don't know the current status very much, 
but patches for MacLinux hadn't been integrated with official kernel source 
code when I looked at it. If Gentoo does not get them included, you need to 
apply patches yourself.

- Make sure that you pass correct parameters to the kernel, especially a 
parameter to the video driver. Otherwise, nothing will be displayed.

Another option is to use legacy boot by installing GRUB compiled for PC BIOS 
to the partition for Gentoo. I think recent versions of Intel Mac should 
support legacy boot by default. But, for now, GRUB does not support 
chainloading a legacy boot loader directly, so you will have to boot it up 
from the built-in selector, or use something else, such as refit, or 
implement this feature in GRUB. As I myself haven't played legacy boot well, 
I don't know how to set up this kind of configuration precisely (yet).

BTW, this report seems to be a proof that x86_64 starts up in 32-bit mode even 
on EFI, well, in Intel Mac. So do we really need to implement 64-bit support 
for x86_64?

Thanks,
Okuji