GPT boot from 2nd. disk fails
Andrey Zonov
andrey at zonov.org
Thu Aug 16 11:15:47 UTC 2012
On 8/16/12 11:06 AM, Daniel Braniss wrote:
>> On Wednesday, August 15, 2012 4:46:28 am Garrett Cooper wrote:
>>> On Wed, Aug 15, 2012 at 1:27 AM, Daniel Braniss <danny at cs.huji.ac.il> wrote:
>>>> hi,
>>>> this host has to disks:
>>>> sa0> gpart show
>>>> => 34 976773101 ada0 GPT (465G)
>>>> 34 128 1 freebsd-boot (64k)
>>>> 162 4194304 2 freebsd-ufs (2.0G)
>>>> 4194466 33554432 3 freebsd-swap (16G)
>>>> 37748898 939024237 4 freebsd-zfs (447G)
>>>>
>>>> => 34 976773101 ada1 GPT (465G)
>>>> 34 128 1 freebsd-boot (64k)
>>>> 162 4194304 2 freebsd-ufs [bootme] (2.0G)
>>>> 4194466 8388608 3 freebsd-swap (4.0G)
>>>> 12583074 964190061 4 freebsd-zfs (459G)
>>>>
>>>> but no amount of magic will cause boot from the second disk, it will
>> always
>>>> boot from the first disk.
>>>>
>>>> any insights?
>>>
>>> Use boot0cfg -s 5 (untested with GPT disks)?
>>
>> Will not work with GPT disks. They use /boot/pmbr to boot, not /boot/boot0.
>>
>> If you can get your BIOS to explicitly boot ada1 from the start via a BIOS
>> setting, that should work. Another option would be to break into gptboot's
>> prompt (similar to breaking into boot2) aud typing in 'ad1p2:/boot/loader' or
>> some such. If that works you should even be able to write that to
>> /boot.config on ada0p2's filesystem.
>
> sorry, as usual my questions are a bit terse :-),
> I want to switch between roots either at boot time (this is very tricky now,
> since breaking into boot2 needs very fast fingers) or before reboot.
> btw, it's 1:ad(0p2)/boot/loader
> also, since the disks are hot swap, i can switch between them, but I realy
> want to do it via software!
>
> the bootme trick did work, on a different host/setup and sometime ago.
>
> before GPT, when we had MBR, I could switch between slices/partitions either
> via the menu or via boot0cfg, so maybe I should go back to mbr.
>
You can erase boot record of the first disk, then your BIOS will try to
use second one. Be careful, some BIOS'es try only first disk.
--
Andrey Zonov
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