i had a issue with uefi and grub2 today, found out a realy simple solution

  • boot into a live cd (uefi mode)
  • mount /dev/sda1 /boot
  • grub-install --target=x86_64-efi --efi-directory=/boot/ --bootloader-id=grub --recheck --debug
  • grub-mkconfig -o /boot/grub/grub.cfg

found some of the info @ slackware docs