In message <20040521180916.GV7278@snowdrop.l8s.co.uk>, David Laight writes:
>On Fri, May 21, 2004 at 08:09:51AM -0400, Steve Bellovin wrote:
>> I'm trying to install a new disk for my laptop.  I copied the contents of
>> the old one, but when I try to boot I get "Error 3" when I select the
>> NetBSD partition.  
>
>"Error 3" means that the magic number (0x55, 0xaa) wasn't found in the
>first sector of the NetBSD mbr partition.
>
>> Since I get a partition selector, and since I can boot the Win2k
>> slice, I assume that the mbr boot is fine.  I tried running
>> 
>> 	installboot /dev/rwd0a /usr/mdec/bootxx_ffsv1
>> 
>> from the utility menu of a -current installation CD I have; I still get
>> the same error.
>
>Does the 'a' partition start at the beginning of the NetBSD partition?
>That is where the bootxx_ffsv1 file has to be written to.
>(The copy is nothing clever, but must avoid stomping over the label
>in the 2nd sector of the partition.)
>

Ah -- that seems to be the problem.

1: NetBSD (sysid 169)
    bootmenu: NetBSD
    start 21546000, size 56594160 (27634 MB, Cyls 1425-5168)

 a:    567000  21549780     4.2BSD   1024  8192 40504  # (Cyl.  21378*-  21941*)


Now to figure out how best to fix it...

		--Steve Bellovin, http://www.research.att.com/~smb