Re: Get/set UEFI variables or NVMe driver?

[JZB]

On 3/26/24 20:00, Marek Marczykowski-Górecki wrote:
> Hi,
>
> Is there a command for getting/setting UEFI variables? I see
> grub_efi_{get,set}_variable functions in the source code, but can't find
> if it's connected to any command. Alternatively, is there an NVMe driver
> for grub?
>
> I know the alternative looks a bit weird, so let me explain. I use
> grub2-efi loaded over PXE to boot different systems depending on some
> external settings (a config file loaded over network too). One of the
> boot paths is booting Linux that is installed on the local disk. With
> SATA it's simple - I can load grub.cfg from the local disk and jump
> there. But for NVMe, grub doesn't see the disk when it's loaded from
> network (my guess is that firmware doesn't load its NVMe driver when
> booting from network). The same grub can access the disk when loaded
> from local disk. My current workaround is booting Linux (loaded
> from network too) that sets BootNext variable to local system and
> reboot. Booting whole Linux kernel just for that feels silly...
> So, I'd like to set the BootNext from grub directly.
>
> An NVMe driver would solve the problem for me too, but I guess that's
> much more work (for a rather niche use case, I realise). And the BootNext
> approach is more reliable anyway, because it ensures the grub version
> matching its config, and would work with non-grub bootloader too.

Try this in your PXE grub.cfg:

menuentry 'Local Boot'
{
  exit
}

BIOS will interpret this as a failure and move on to the next device 
after PXE boot.  Arrange that in your boot order, and you should get 
your local NVMe boot.  Granted, its not very flexible, but the better 
solution would be more work and require that grub tell the BIOS to 
"reconnect" its partition driver (long story).

--jzb