[UEFI] GRUB 2 installation method

[Andrew Gunnerson]

With more UEFI based systems now, it's pretty important that GRUB 2 is installed correctly on those systems.

The way Ubuntu installs GRUB 2 on UEFI systems puts the GRUB 2 configuration files in EFI_PARTITION/efi/ubuntu/grub.cfg. I'm not sure how it actually is installed, but the behavior can be replicated by installing GRUB 2 with:

grub-install --boot-directory=/boot/efi/efi --bootloader-id=ubuntu --force --recheck

The problem with this is that the configuration files are inconsistent with the BIOS version GRUB 2, making all scripts that depend on the /boot/grub directory structure useless.

If GRUB 2 UEFI is installed this way:

grub-install --bootloader-id=ubuntu --force --recheck

GRUB 2 will continue to use /boot/grub, just like the BIOS version and generates a grubx64.efi file in EFI_PARTITION/efi/ubuntu/ that will ALWAYS load /boot/grub/grub.cfg from the /boot partition, which the grub-install script identifies during installation. This is exactly the same behavior in the BIOS version, where GRUB 2 in the MBR always boots from the /boot partition that was mounted during installation.

Not only does this method make things more consistent, it can also shave off a little bit of the boot time, because the EFI partition will no longer need to be mounted every boot.

[Andrew Gunnerson (cxl)]

This bug was marked as a duplicate of 879858, but I don't think that they're the same bugs. The other bug is about a kernel error when using efibootmgr while installing GRUB EFI. This bug suggests a better command that can be run to install GRUB EFI (more of a feature enhancement).