Re: How to control booting via BIOS vs booting via EFI?

[Martin Husemann <martin%duskware.de@localhost>]

On Sun, Oct 12, 2025 at 04:21:51PM +0200, Johan Stenstam wrote:
> Any help would be much appreciated.

I would be suprised if NetBSD/xen could not boot via UEFI but actually all
my xen machines still use BIOS boot (mostly for historical reasons).

We have multiboot2 support, so technically it is unclear to me why xen
would fail.

However, unrelated to that: you can force BIOS boot by installing from
the amd64-bios-install.img[1] USB image and removing all existing partitions
starting from scratch.

Or you can manually modify your exixting setup by something like:

 - remove the EFI partition (details depend on whether you used MBR
   or GPT partitionining)
 - install the proper first stage booloader (either via "gpt biosboot"
   or by "installboot" if using MBR)
 - copy /usr/mdec/boot to / on the NetBSD root partition

Martin

1) https://nycdn.netbsd.org/pub/NetBSD-daily/netbsd-10/latest/images/NetBSD-10.1_STABLE-amd64-bios-install.img.gz
or https://nycdn.netbsd.org/pub/NetBSD-daily/netbsd-11/latest/images/NetBSD-11.0_BETA-amd64-bios-install.img.gz