mknbi is a program that makes network bootable images for various operating
systems suitable for network loading by Etherboot or Netboot, which are ROM
boot loaders. If you are looking to boot using PXE, look no further, mknbi is
not what you want. You probably want something like PXELINUX which is part of
the SYSLINUX package.

WWW: http://www.etherboot.org/