9.1 install wipes out gpart boot blocks? [solved]

[Gary Aitken]

On 01/30/13 15:02, Robert Huff wrote:
> 
> Gary Aitken writes:
> 
>>  I used gpart to set up a new disk,
>>  then went through a 9.1 install.
>>  Everything seemed to go fine, but when time came to boot the new drive,
>>  it wouldn't boot.
> 
> 	While the "it wouldn't boot" is catastrophically imprecise,

I knew I'd get hammered on that :-)
Screen goes blank, 
spinner spins maybe two notches, then just sits there.
So gptboot isn't even started.

> I
> had what sounds like a similar problem about a month ago.
> 	I installed from the 9.0 CD and everything appeared to go
> correctly.  However, on final re-boot the loader couldn't identify
> the root partition.
> 	The solution was to identify the disks using the GPT labels in
> fstab.
> 	Check the archive of questions@ for more details.

Found the archive, didn't really help.

However, I did rewrite both boot areas and that solved the problem:

gpart bootcode -b /boot/pmbr ada3
gpart bootcode -p /boot/gptboot -i 1 ada3

So apparently the 9.1 installer wipes out at least the boot code in partition 1.
Since the spinner went a few notches, I suspect the primary boot block is ok,
but it crashed when it can't execute the gptboot code.