Dear Alexander,

right now it's not possible to specify a device for the memdisk image.
This makes it impossible to boot out of the box with a separate /boot
partition. I have marked the bug as important as this is an option
that's available in the debian installer. I've implemented a trivial two
line fix that

- Adds a BOOTDISK parameter to /etc/default/grub-imageboot
- Prepends that to the BOOTDISK in /etc/grub/60_grub-imageboot

I realize that this should probably be automated, and would be happy to
work on it some more and prepare a proper patch. It seems like calling
grub-probe with efi_hints as target could help, but I don't know enough
about grub to make an informed decision. I also think that simply adding
the parameter is probably good enough.

Thanks for developing + maintaining this package,

Nicolas