Replying to my own post.

I was able to get my system to automatically boot from my drive with:

  /usr/mdec/installboot -v /usr/mdec/biosboot.sym /dev/rwd0f

(Notice that I used the "f" partition.)

I realized I was trying to boot from the wrong place before.

On Mon, 20 Nov 2000, Jeremy C. Reed wrote:

> I have one drive which has four partitions (because at one time, I planned
> to try booting four different OS's). It was installed with a boot selector
> that defaulted to the third partition (partition number 2) -- NetBSD. This
> has been working since installed in February. At first, all I used was the
> NetBSD partition; but over time I needed more space, so I used disklabel
> and started using the other partitions.
> 
> I had never used the first partition. Last week, I added a new slice from
> the first partition and did a newfs -- this worked great and added a lot
> of needed space.
> 
> Today, the first time I rebooted, it would just hang at the boot menu. I
> am able to boot with the install floppy: "boot wd0a:netbsd".
> 
> Some things I have tried include:
>  fdisk -i
>  /usr/mdec/installboot -v /usr/mdec/biosboot.sym /dev/rwd0a

> #        size   offset     fstype   [fsize bsize   cpg]
>   a:   238896  6331248     4.2BSD     1024  8192    16   # (Cyl. 6281 - 6517)

>   f:  3164049       63     4.2BSD     1024  8192    16   # (Cyl.    0*- 3138)

   Jeremy C. Reed
   http://www.reedmedia.net/