mlel...@serpens.de (Michael van Elst) wrote: > bea...@sdf.org (beaker) writes: > > > gpt biosboot [-A] [-c bootcode] [-b startsec] [-i index] [-L label] > > >for a gpt partitioned disk or is this relatively recent addition > >just an alternative of convenience? > > A regular BIOS (not UEFI) loads the MBR from block 0 of a disk. > The boot program in the MBR checks the embedded partition table > and then continues to load a PBR from the first block of the > active partition. The PBR is then executed and continues with > the boot process. > > MBR = master boot record > PBR = partition boot record > > We maintain the regular MBR (and the partition table) with > the fdisk program (and the PBR with the installboot program). > > If you use a GPT, there is only a "protective MBR" for compatibility. > But it's still possible to include a boot program in that "protective MBR" > that understands a GPT. This allows to use BIOS to boot from a > GPT formatted disk. > > We maintain the GPT with the gpt program and 'gpt biosboot' > stores such a special boot program. > > In your case however, you provide your own MBR (with grub) > and 'gpt biosboot' would just overwrite grub with our boot > program.
Thanks for that explaination. It does seem like I could do a targeted storage with # gpt biosboot -A -i 3 # gpt3 == FFS netbsd partition which is how I managed to wipe out GRUB the first time. Also is the default bootcode (XXX) correct or should another boot code be used via '-c' for this non-UEFI + gpt scheme? -B
