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Re: UEFI: can running grub-install help after a motherboard change?


From: Pascal Hambourg
Subject: Re: UEFI: can running grub-install help after a motherboard change?
Date: Thu, 4 Aug 2022 22:41:04 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:91.0) Gecko/20100101 Thunderbird/91.10.0

Le 04/08/2022 à 22:26, Sébastien Hinderer a écrit :

Still not subscribed to the list, sorry, but I would like to ask your
help again because I have to change my motherboard again and I would
like to aovid relying on sighted assistance as much as possible, except,
of course, the one of the engineer who is going to do the change.

Pascal Hambourg (2022/02/22 23:28 +0100):
Le 22/02/2022 à 20:54, Sébastien Hinderer a écrit :

Given that running grub-install had already been done with my former
motherboard, does it make sense to run it again with the new
motherboard? Does grub-install somehow interact with the motherboard to
let it know it supports UEFI mode?

Yes and yes. The normal way of booting in UEFI mode requires to "register"
the boot loader in the EFI boot variables which are stored in the
motherboard non volatile memory. EFI boot variables can be read and written
with efibootmgr.

A way to not depend on EFI boot variables is to install the boot loader in
the "removable media path". You can do it with

grub-install --removable

So, am I correct that I can run this command before changing the
motherboard (so with the old motherboard in place) and it will make the
EFI boot work also with the new motherboard? Is that correct?

Yes, it should boot from the "removable media path" if the UEFI firmware is not too flawed.

In Debian, you can use

grub-install --force-extra-removable

to install GRUB in both the normal location (and update EFI variables) and
the removable media path.

And then I could for instance use this command once the new motherboard
is in place, to make it sure grub is installed ont he motherboard
itself, too? Does all this make sense?

It is rather an alternative to the previous command on Debian installations (since Buster, --removable may install a weird kind of GRUB signed image which did not work well on one of my machines). If the new board can boot from the "removable media path" then you do not need to create an EFI boot entry.



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