Subject: Re: booting from an alternate partition?
From: David Laight <firstname.lastname@example.org>
Date: 07/15/2002 00:45:21
> I'd like to be able to menu-select from the mbr_bootselect thing that I
> want to boot from wd1i, rather than wd1a.
Yes - not unreasonable IHMO.
Unfortunately the (standard) 'mbr' code doesn't tell the 'pbr' code
where it was loaded from. This means that although you execute the
first sector of ptn 2, that code reads in the rest of the 2nd stage
bootstrap from ptn 1 (there may be trouble if they are different
versions - I'm not sure).
By the time the bootloader is entered (read in by the extended 'pbr'
code) all history of whether you typed F1 or F2 has long since vanished!
Now I have a version of the mbr code that does pass the sector number
through to the pbr code, and hence into the boot code.
(So F1 boot 1.5.x and F3 1.6.x on my system)
However I have 2 disklabels - and setting the second one up was 'fun'.
Maybe leaving the disklabel on the lowest numbered netbsd partition 
and using the sector number to select a slice is a better idea?
Obviosly if the sector number is invalid wd<n>a would be used.
 might be safer to write it to all of them....
David Laight: email@example.com