Re: EFI boot: 'could not prepare Boot variable: Invalid argument'

[post]

> On Sun, Nov 6, 2022 at 4:58 AM <post@thomasdanckaert.be> wrote:
> > 'Could not prepare Boot variable: Invalid argument'
>
> You have not yet rebooted, have you?
>
> What do you see with this command?
>
>     ls /sys/firmware/efi/vars/

efivars --list produces the following output:

8be4df61-93ca-11d2-aa0d-00e098032b8c-BootCurrent
4d1ede05-38c7-4a6a-9cc6-4bcca8b38c14-FirmwareFeatures
8be4df61-93ca-11d2-aa0d-00e098032b8c-ErrOutDev
8be4df61-93ca-11d2-aa0d-00e098032b8c-LangCodes
4d1ede05-38c7-4a6a-9cc6-4bcca8b38c14-FirmwareFeaturesMask
8be4df61-93ca-11d2-aa0d-00e098032b8c-ConOut
eb704011-1402-11d3-8e77-00a0c969723b-MTC
8be4df61-93ca-11d2-aa0d-00e098032b8c-BootFFFF
8be4df61-93ca-11d2-aa0d-00e098032b8c-ConOutDev
8be4df61-93ca-11d2-aa0d-00e098032b8c-Lang
8983fd2d-113c-4e2b-8f47-0abfeb20a41a-SmmS3NvsData
af9ffd67-ec10-488a-9dfc-6cbf5ee22c2e-AcpiGlobalVariable
4dfbbaab-1392-4fde-abb8-c41cc5ad7d5d-Setup

> Diagnosing boot problems can be difficult even when sitting in front
> of the equipment. I believe your system booted via the legacy boot
> sector method instead of UEFI, which made the EFI variables
> unavailable.
>
> If so, the only way to fix it is to boot via EFI.
>
> > I fear my system is currently unbootable.
>
> In Guix, you should have old system generations available in the GRUB
> menu. That is your preferred method.

My fear is that the GRUB menu will not come up, because the bootloader 
is likely broken (at least that's what happened last time I ran into 
issues with EFI boot, though that was on another machine).  Is there 
anything I can try from the still running system, or should I just try 
to reboot and see what happens?

> You may also be able to manually link the EFI image you wish to load
> via the "removable media path". A third option that I have used is to
> load your kernel directly via its EFI stub. The two latter options may
> require further help from this list and lots of patience. They also
> carry a higher risk of failure.

I don't know how I'd go about these two options, so I'd definitely like 
some help with that.  I've also read about rEFInd, which (from my 
understanding of the documentation) might be able to boot the existing 
kernel.  Not clear if that's the way to go.

Thomas