Chain-loadable UEFI firmware?

bifferos · 01-31-2021, 12:28 PM

I have an old laptop that I want to use to boot an UEFI USB stick. I wondered if there is some magic that I can put on a bootable DVD to boot the system into something that behaves like a UEFI PC, recognizing the fat partition on the USB and booting that in turn.

Is it possible?

thanks!

Emerson · 01-31-2021, 12:55 PM

No, but you can make this USB stick bootable in both, legacy and EFI mode. How hard it is depends on what exactly is on that USB stick. For instance, once upon time I knew nothing about UEFI, but I wanted to be ready for it. So I created ESP partition during install and placed my kernel(s) there. Using GPT partition table I resorted to legacy boot from MBR. Then one day I built myself an EFI stub kernel. Now I was able to boot in EFI mode. I still could boot the very same kernel also in legacy mode, it is just a matter of going into BIOS and choosing CSM mode.

colorpurple21859 · 01-31-2021, 02:15 PM

Another option is to set up grub on the usb to boot in both legacy and uefi mode.
As has already been said it depends what is on the usb.

Quote:

I wondered if there is some magic that I can put on a bootable DVD to boot the system into something that behaves like a UEFI PC, recognizing the fat partition on the USB and booting that in turn.

Not sure what you mean by this, does the old laptop not have the ability to boot from a usb?

TorC · 01-31-2021, 03:04 PM

Quote:

Originally Posted by Emerson

No, but you can make this USB stick bootable in both, legacy and EFI mode. How hard it is depends on what exactly is on that USB stick. For instance, once upon time I knew nothing about UEFI, but I wanted to be ready for it. So I created ESP partition during install and placed my kernel(s) there. Using GPT partition table I resorted to legacy boot from MBR. Then one day I built myself an EFI stub kernel. Now I was able to boot in EFI mode. I still could boot the very same kernel also in legacy mode, it is just a matter of going into BIOS and choosing CSM mode.

Ran across this from SourceForge -- similar to what you are saying, it seems to me. Don't know it it works for OP.

bifferos · 02-01-2021, 06:16 AM

The laptop recognises bootable USB in theory but I've found it to be incredibly fussy about it, and this wasn't the only time I've seen this. I can easily create UEFI compatible boot media on Mac, Windows etc... no special tools required. It just happens that every device that's 'too old' to boot the latest 'bootable' USBs has a DVD, so I figured that would be a nice way to solve the problem. Can understand why such a thing hasn't been created, because it would be just for antiquated hardware.

My last resort is as you say to start going through the various utilities that make an image 'legacy bootable' e.g. WoeUSB and friends, but I didn't get on very well with these in the past.

thanks.

colorpurple21859 · 02-01-2021, 06:55 AM

super grub may do what you want. https://www.supergrubdisk.org/catego...2-disk-stable/
https://www.supergrubdisk.org/super-grub2-disk/

bifferos · 02-02-2021, 06:32 PM

It's a little hard to figure out exactly what it does from the docs, but it does seem worth trying, thanks.