Not all platforms that NetBSD runs on support fdisk.  Besides, until 
  recently you were limited to four fdisk partitions, which was a 
  nuisance for NetBSD.

Indeed, very few platforms natively use BIOS-style labels.  A key
point is that disk labels have to match the hardware/PROMs native
expectations for finding and booting a kernel.

  The right answer is a program that can read fdisk labels and generate 
  NetBSD label data.  It shouldn't be too hard to write, either.

You don't even have to write it - mbrlabel(8).

-- 
        Greg Troxel <gdt@ir.bbn.com>