Re: Boot off PCIe NVMe SSD by chain booting into its grub

[Pascal Hambourg]

Le 01/05/2021 à 14:32, Vladilen Kozin a écrit :
> - install your OS on that SSD,
> - put /boot onto USB stick
> - copy over whatever incantation /dev/SSD/boot/grub/grub.cfg has to
> load the kernel and initrd,
> - but also copy your kernel ash initrd image over to /boot/ on that
> USB and have Grub boot into that.

You do not have to copy anything. Just mount a USB drive partition as 
/boot at installation time, and install GRUB in that drive MBR.

> So, instead I would like to also employ indirection but somehow chain
> into Grub installed on that SSD. That's probably not Grub's own
> "chain" cause it still won't see that drive.

Indeed.

> Maybe I could put some
> kernel / initrd on USB that would boot with those drives visible and
> then have it run Grub on SSD somehow?

The kernel cannot run the boot loader. It only works the other way around.

> Or maybe I can load a kernel and
> initrd into memory which will probe and find that drive and then Grub
> would be able to see somehow?

You may be able to do this with kexec.

> Or maybe there's some magical Grub module already that can find these
> PCIe NVMe SSDs?

AFAIK GRUB has no native NVMe driver yet.