Re: Two GRUB setup can boot one each of two installs, but not the other, why?

[Michael Evans]

On Thu, Dec 17, 2009 at 3:49 PM, Yavuz Onder <address@hidden> wrote:
> Michael Evans wrote:
>>
>> On Thu, Dec 17, 2009 at 5:27 AM,  <address@hidden> wrote:
>>
>>>
>>> Hi,
>>>
>>> I have a very strange GRUB problem, that got me totally stumped.
>>> [my info removed for brevity]
>>
>> Your problem is most likely caused by an over-helpful BIOS which is
>> re-mapping physical devices so that whichever device is selected as
>> the 'boot' device is setup as the 0th BIOS drive.
>>
>> In this case for one of the two grub installs you must refer to the
>> drive your Linux installs are on by some other name; very likely by
>> using a custom device.map file to specify that (hd1) is actually
>> /dev/whatever.
>>
>> Thus one drive would be installed as normal.
>> The other drive would be setup (manual grub install) with a device-map
>> file.
>>
>> Since the device-map file would re-define the hard drives the actual
>> grub.conf file can be the same for both installs.
>>
>>
>
> Thanks, but I am not using any disk drive spec at all, but only UUIDs.
>
> I am pretty much forced to work with UUIDs as I frequently add extra disks
> and (hdn,m) format always poses a moving target.
>
> Can you suggest a work around with UUIDs left in picture? Where is that
> "device-map file"? Will removing it help?
>
> I can get rid of one of the MBRs happily if the remaining one would work.

Your KERNELs are using UUIDs.  In order to _load_ grub and the
kernel/initrd grub needs to know what _BIOS_ drive to use.  It may be
worth noting that given your setup (linux on the secondary drive)
probably the one with the BIOS drives out of your desired order is the
only one that boots for you.  In that case you'd also need to use the
device.map file to specify the proper order of the drives before
switching to it.