boot problem after freebsd-update from 9.1-RC2 to 9.1-RC3

[Warren Block]

On Tue, 20 Nov 2012, freebsd at johnea.net wrote:

> On 2012-11-20 14:28, Gary Aitken wrote:
>> On 11/20/12 13:34, freebsd at johnea.net wrote:
>
>>> freebsd-update upgrade -r 9.1-RC3
> ...
>>> "Not UFS"  "No ada0" "No boot"
>
>>
>> Seems like it isn't supposed to work for 9.1-RC2
>>
>
> I previously used binary update to migrate from 9.0 to 9.1, via:
>
> freebsd-update upgrade -r 9.1-RC1
> freebsd-update install
> reboot
> freebsd-update install
> reboot
>
> I'm starting to think having the swap partition in gm0s1a and the booting UFS partition in ada0s1b is the problem:
> http://forums.freebsd.org/showthread.php?t=31954
>
> The "Not UFS" error comes immediately on boot.
>
> If I boot from rescue media, I can start the gmirror, mount it and chroot into it.
>
> The whole install seems fine except for the first stage boot loader finding the UFS partition.
>
> A handy bootloader config trick would be greatly appreciated!

boot(8) says

   The automatic boot will attempt to load /boot/loader from partition
   `a' of either the floppy or the hard disk.

You could try setting the correct device path in /boot/boot.config, but 
I suspect that won't be read until too late.

gptboot looks for the first UFS partition.  Maybe /boot/boot can be 
modified to do that also.