20241022 11:34
I convinced myself to run OpenBSD on my Mac from 2011.
A three problems matter.
a) How to access the boot menu: press Option / Alt key while starting your Mac.
b) Be sure to not compromise the existing OS: you usb installation shouldn't mount
external hds by device node references; or try
http://fuguita.org project;
c) How to fix a missing EFI boot (the Mac requires it)
You can go ahead adding your EFI boot in this way:
1) backup your usb stick;
2) note down, somewhere your OpenBSD sector boundaries and offset+size of the last existing partition.
3) check you have some unused space on your stick, actually almost 300mb;
4) fdisk -i -b blocks[@offset[:EF]] sdx (<- replacing sdx with your usb disk)
stating carefully the @offset of the new partition
like the offset+size of the last existant partition;
NB: if you calculate well offset and size of the new partition,
without overwriting the existing data you should not lose anything.
5) confirm to fdisk the writing of the mbr; this will create
one only EFI area, partition [i], but..
6) at this point it seems you lose everything because fdisk
if you go in disklabel everything disappeared;
the matter is simple: you just created an empty zone
out the used space, so the subject become to recreate the OpenBSD
area in fdisk, with related boundaries (covering the full disk)
and going in disklabel you will notice everything is back;
7) remaining in disklabel add the partition [i] yourself like MSDOS
with the required offset and size; save labels;
8) now launch: newfs_msdos sdxi (<- replacing x with your usb disk)
9) manually copy BOOTX64.EFI and BOOTIA32.EFI from /usr/mdec to your
new partition in efi/BOOT (BOOT should be uppercase).
Faceborg