Re: [gentoo-user] Mac Mini with Grub booting Mac OSX and Windows?!

[Andrea Conti <alyf@alyf.net>]

>> The real problem is that while rEFIt/rEFInd, OSX and Linux have no
>> problem dealing with a GPT partition table, Windows only supports MBR.
>> (Windows 7+ supports GPT partition tables but it can only boot from a
>> GPT disk in EFI mode.
> 
> So, let us assume we have in the game:
> 
> Windows 7 Ultimate Edition
> Gentoo Linux
> and Mac OSX (latest version)
> 
> then we are all on the same side accessing the same partition table
> type, no?!

No. :)

While Intel Macs are EFI platforms, they have an early and quirky 
implementation that cannot properly boot Windows in EFI mode, so you're 
stuck with booting in BIOS emulation mode, which in turn means that 
Windows will not use the GPT table. This is a really stupid Windows 
limitation, but we can't do anything about it.

The Linux kernel can use GPT with no restrictions, however booting is 
another story.
Booting directly from GPT requires a GPT-aware bootloader such as GRUB 
2. Alternatively you can use GRUB legacy, but you need an entry in the 
MBR for the boot partition. The root partition (and any other 
partitions) need not appear in the MBR, as they are mounted by the 
kernel.

OSX uses GPT natively and does not need MBR entries for its 
partition(s). The only exception is if you want read-only access to an 
HFS+ partition in Windows through the driver provided by BootCamp; in 
that case you need to ensure that the first entry in the hybrid MBR 
covers the HFS+ partition you want to access.

andrea