OS X dual boot criterion problems

[Chris Murphy]

On Thu, Dec 4, 2014 at 12:41 AM, Adam Williamson
<adamwill at fedoraproject.org> wrote:
> Hi, folks. Talking to cmurf, our resident OS X dual boot expert, on
> #fedora-qa, it's become clear that when we adopted the OS X dual boot
> criterion a few weeks back, we didn't have a good understanding of the
> current state of that code and particularly upstream grub's support for
> booting OS X via UEFI. Basically it seems that booting OS X from grub
> didn't work then and doesn't work now and we can't realistically fix it,
> so we shouldn't have put that criterion in place because it's not
> something we can actually viably achieve.
>
> cmurf, roshi, kparal and I voted +1 to removing the criterion on that
> basis. I'm hoping cmurf will be kind enough to look at the issue again
> for the F22 cycle, in consultation with pjones if necessary, so we can
> put a realistic requirement in place before we get into F22 Alphas.
>
> If no-one has any objections, we'll make the removal formal ahead of
> tomorrow's Go/No-Go meeting for 21. Thanks folks!

Gist: EFI GRUB still gets these legacy OS X boot options that were
designed to permit CSM-BIOS GRUB to EFI boot OS X. They don't work
from EFI GRUB though.

As far as I can tell there's no upstream bandwidth/interest in fixing
this; even if it means just suppressing the creation of the entries,
rather than chainloading the Apple bootloader. So I think the issue is
not a QA issue right now, but needs to be bounced back to desktop@ for
the Workstation WG to maybe use some recruitment influence if they
want to see this fixed.
http://lists.gnu.org/archive/html/grub-devel/2014-10/msg00044.html

A challenge with grub2-mkconfig creating an entry to chainload Apple's
boot.efi, is with recent on-disk format changes in OS X 10.10 since
this last October. It means os-prober will need to become aware that
the boot.efi it's looking for is now on an Apple Boot [1] partition.
I'm not sure what's involved in doing that work compared to just
suppressing the creation of entries that don't work anyway.


[1]
48465300-0000-11AA-AA11-00306543ECAC HFS+ partition type, no longer
used except for external/removable media, this is what os-prober looks
for today
426F6F74-0000-11AA-AA11-00306543ECAC Apple Boot partition type, is
JHFS+ format, is where boot.efi is located
53746F72-6167-11AA-AA11-00306543ECAC Core Storage PV partition type,
OS X's version of LVM, the LV OS X is on could be encrypted but in any
case right now we can't mount the volume until we have Core Storage
support on linux.

-- 
Chris Murphy