Trying to understand the boot process

[Pierre Lamy]

I've got a nice little Atom box with a CF and hard drive, and I can 
currently boot NanoBSD off the flash no problem.

I would like to optionally select the HD as a bootable device, and it 
does show up in the boot:

1  FreeBSD
3  FreeBSD
5  Drive 1

Now, I have already set a slice and put /boot in ad4s1a, and FreeBSD is 
manually installed out of a chroot'ed install (tar'd on seperate system 
and extracted correctly to the appropriate local HD filesystem) but I 
can't figure out how to actually get it booted, it seems to be missing 
the MBR?

I have already RTFM, and used bsdlabel -B ad4s1, and also tried fdisk 
-B. I simply get the "Reboot and select proper boot device or insert 
boot media..." message.

Does anyone have any suggestions?

My second question is how to label the boot options so that 1 says 
NanoBSD, 3 doesn't show up at all, and 5 days FreeBSD.

-Pierre