Re: gpt booting status?

[David Laight <david%l8s.co.uk@localhost>]

On Wed, Dec 24, 2014 at 09:30:31PM -0500, Greg Troxel wrote:
> 
> and a further question:
> 
>   I know /boot (with MBR) can skip the raidframe header.  So given a
>   disk with a single MBR partition of type RAID, and an inside-the-RAID1
>   disklabel with raid0a starting at 0, booting works.  (I'm sure because
>   I do this all the time.)
> 
>   But, if I have gpt, with a RAID partition, and in the RAID1 have
>   another gpt label, and in that a partition, is there any way to boot
>   from that?  Basicallly I'm thinking
> 
>     sd0
>       A=gpt partition 1, type raid, starts at 1024, big
>         raid0  (so starts at 1024*64)
>           B=gpt partition 1, starts at say 1024+64+64
> 
>    and would like the bootxx_ffsv2 code written to the beginning of
>    A to see type 'raid', skip 64, and then interpret gpt vs mbr and find
>    the active inner gpt partition.

The code that reads /boot (last time I looked) doesn't inspect any inner
labels (of any type). It just had a nasty hack to look for a filesytem
a further 64 sectors down the disk if it doesn't find /boot in the
expected place.

Maybe a gpt disk has space for a larger boot image?
In which case it might be possible to have more code to find /boot.

	David

-- 
David Laight: david%l8s.co.uk@localhost