Wrong /boot/grub/grub.cfg processed after change of GRUB_DISTRIBUTOR

[UlfZibis]

I have 2 Ubuntu 64-Bit installations on 2 different partitions.
I have added a 2nd UEFI boot directory:
/boot/efi/EFI/ubuntu-64
After booting into the 2nd installation, I have changed in /etc/default/grub:
GRUB_DISTRIBUTOR="Ubuntu-64"
After grub-install and update-grub I got new .efi files in /boot/efi/EFI/ubuntu-64 and a new /boot/grub/grub.cfg and /boot/efi/EFI/ubuntu-64/grub.cfg refers to the partition of the 2nd installation.

When I again boot via /boot/efi/EFI/ubuntu-64 the /boot/grub/grub.cfg of the 1st installation is processed instead the one of the 2nd installation. I think, this is wrong.

Looking into /boot/efi/EFI/ubuntu-64/grubx64.efi of the 2nd installation with a hex editor I find the string EFI/ubuntu instead EFI/ubuntu-64.

The failure can only be avoided when installing GRUB with --no-uefi-secure-boot.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[UlfZibis (ulf-zibis)]

Ubuntu boot loaders (here grubx64.efi), which are signed for secure boot, internally always refer to grub.cfg in the boot directory "EFI/ubuntu/" in the EFI system partition. If changed e.g. via hex editor, the UEFI boot signature check of it will and must fail.

A fix could be to remove the fixation on "EFI/ubuntu/" in grubx64.efi and instead to detect the belonging "EFI/xxx/grub.cfg" by examination of it's own location "EFI/xxx/".