[SOLVED] Thought Experiment

business_kid · 09-08-2020, 02:27 PM

This is a Post I made on the hardware forum Thought Experiment And nobody is crying yet over spilt milk.

The question seems to boil down to this: will the RazPi tolerate an X86 grub MBR on the /boot partition? It's just the MBR, I gather.

So on a RazPi: OS will ignore grub and cow-tow to the eeprom's tune.
And on X86_64, it will read the mbr, jump to the appropriate partition, and boot there. Everything else can be sorted.

Any contributions welcome.

elcore · 09-12-2020, 02:32 AM

No experience with RazPi or EFI, but I did read the other thread in hardware forum.
What is normally done on x86 when the loader is not flexible; chainloading is configured in another loader.
In case of 2 loaders where none is flexible, they pass the loading job to one another with a chain module.

business_kid · 09-13-2020, 04:02 AM

The very first thing the RazPi 4 EEprom does is d/l the firmware file bootcode.bin, which is the gpu firmware. I suppose the only test of whether a dual boot will work is to install a grub mbr to a usb. That will pick up in an X86 box, I hope, and try it. I will report back. I'll just need to investigate grub a little. I presume it's the usual?

Code:

grub-install /dev/sda

sndwvs · 09-13-2020, 05:12 AM

try using bootmenu

michaelk · 09-13-2020, 08:15 AM

I don’t think it will matter. The eeprom only cares about reading the vfat partition for the firmware etc and eventually booting the kernel. It cares not about the 0-445 bytes, just the partition table. What is in the MBR is just grub stage 1. I would not expect problems but without testing you never know exactly what will happen.

fatmac · 09-13-2020, 08:29 AM

Syslinux is another option, it loads Linux from a FAT partition.

https://www.syslinux.org/old/faq.php

Exaga · 09-13-2020, 02:44 PM

Quote:

Originally Posted by fatmac

Syslinux is another option, it loads Linux from a FAT partition.

Linux and FAT partitions aren't exactly the best of friends. sync;sync

business_kid · 09-14-2020, 04:02 AM

I'm surprised. I always found linux handled fat ok. Now fat32 is a crap filesystem imho, and fat16 is worse again. Windows has dropped fat, IIRC. You have to d/l a windows driver for it. And there's poor security, no ownership bits, etc. etc.

Anyhow, fatmac has tried it(Thanks, fatmac), it being grub mbr on a FAT RPi boot partition and it works. Thank you all for your thoughts. That leaves open this sort of dual boot usb

RPI /boot
X86 /boot & maybe EFI
Rpi filesystem
Linux filesystem
Common data partition (for movies, data exchange, weather logs, Rpi & Linux images or isos, whatever).