gpt booting (Was: Re: boot problem after freebsd-update from 9.1-RC2 to 9.1-RC3)

[Warren Block]

On Wed, 21 Nov 2012, Arthur Chance wrote:

> On 11/21/12 05:11, Warren Block wrote:
>> gptboot looks for the first UFS partition.  Maybe /boot/boot can be
>> modified to do that also.
>
> It's a little more complicated than that Warren.
>
> AIUI gptboot first looks (in partition order) for partitions with both the 
> bootme and bootonce attributes set. If it doesn't find any, or if they all 
> failed to boot it then tries booting partitions with just the bootme 
> attribute. It only boots the first UFS partition if no partitions have the 
> bootme attribute set, and IIRC that is for compatibility with the 8.x gptboot 
> which didn't know the boot* attributes.
>
> Confusingly, there's no manual page for gptboot to document this. It's sort 
> of implicit in the gpart manual page, in the section on ATTRIBUTES for GPT, 
> but the best way to understand it is to read the code for gptfind in
>
> /usr/src/sys/boot/common/gpt.c

Well, yes.  The point is that gptboot doesn't just assume that p2, say, 
is where the bootable UFS partition must be.

I've also noted the lack of a gptboot man page, and it's on my long list 
of Things That Should Be Done.  There was a thread on -doc:
http://lists.freebsd.org/pipermail/freebsd-doc/2012-June/020060.html

Help would be greatly appreciated.