Re: wrong hdX designation in grub.cfg

[Andrey Borzenkov]

On Mon, Jan 13, 2014 at 7:13 AM, Chris Murphy <address@hidden> wrote:
>
> On Jan 12, 2014, at 7:19 PM, Andrey Borzenkov <address@hidden> wrote:
>
>> В Sun, 12 Jan 2014 15:59:46 -0700
>> Chris Murphy <address@hidden> пишет:
>>
>>> A normally working grub.cfg contains this entry:
>>>
>>>        search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt4 
>>> --hint-efi=hd0,gpt4 --hint-baremetal=ahci0,gpt4  
>>> d7bc9d0e-7706-44f9-b1a7-ff24b7c360a7
>>>
>>> hd0,gpt4 seems to be wrong.
>>
>> It is just a hint anyway.
>>
>>> At a grub prompt, there is one hd0 entry, and multiple hd1,gptY
>>> entries. These correspond to the partitionless Firewire drive, and the
>>> internal drive respectively. It seems like the firmware presents the
>>> Firewire drive to grub first and therefore is hd0 in grub. But once
>>> booted to linux, the internal drive ends up being treated as hd0 by
>>> grub-mkconfig.
>>>
>>> Firmware bug? Or grub bug?
>>>
>>
>> Neither. Nobody ever said firmware would enumerate devices in the same
>> order as kernel. This is exactly why grub2 stopped relying on it and is
>> using search instead.
>
> Fair enough. Is the most important reference the fs UUID?

Yes

> Would that alone work,

Yes

> or do the hints make finding it by UUID faster?

Yes (as long as hints were guessed correctly of course). If you know
boot time device order and are sure it is reliable, you can always
force this particular order in device.map. This is basically the only
thing this file is good for today.

>
>>
>> Is it BIOS or UEFI system?
>
> Technically neither, it's a Mac. So it's in some Apple zombie land between 
> Intel EFI and UEFI.
>
> Chris Murphy
>