adding boostrap code to boot system

[walt]

Jeremy C. Reed wrote:
> My test laptop has:
> 
> ad0s1 -- NetBSD
> ad0s2 -- unused
> ad0s3 -- FreeBSD
> ad0s4 -- DragonFly
> 
> I used NetBSD to partition ad0s4 for ID 165. The fdisk tool asked me for 
> the boot label name. I entered "DFly".
> 
> I then used the latest official DragonFly CD "installer" to install to 
> ad0s4.
> 
> I chose to skip installing the boot manager, since I already had one that 
> worked for ad0s1 and ad0s3.
> 
> Rebooting gave me a choice for "DFly" but it didn't work and ended up 
> booting my NetBSD.
> 
> I booted the LiveCD again and ran:
> 
> disklabel -B ad0s4
> 
> It complained:
> 
> ad0s1: rejecting partition in BSD label: it isn't entirely within the slice

Frankly, I don't know the answer -- but I'm betting that the error
message above is a red herring.  I say that because I see the same
error every time I boot any machine with both NetBSD/OpenBSD and
FreeBSD/DFly installed.  The two disklabel formats are incompatible
because the Net/OpenBSD disklabel begins numbering sectors at the
start of the physical disk -- whereas Free/DFlyBSD starts numbering
from zero at the beginning of the slice.

I've just learned to ignore that error message altogether.

 > Any ideas on how I can get my ad0s4 partition to boot?

I always use GRUB and I've never had any cause to regret it.  GRUB
doesn't need any boot sectors to be installed because it bypasses
them completely.  It loads /boot/loader directly from the hard disk
in the case of DFly/FreeBSD or loads the NetBSD kernel directly.
(It actually does use the OpenBSD bootsector, but that isn't your
current problem.)

When in doubt:  make a GRUB boot floppy and try it before installing
GRUB to the hard disk.  (Do laptops still have floppy drives?  Dunno.)