boot-update-1.7.4 (null-keyworded) generates grub.cfg with new parameter rootflags=noatime and it's added before rootfstype. This results in, kernel panic during boot with message: unable to find root device, please add correct root="' cmd line. Manually removing rootflags=noatime form grub.cfg workarounds this. System boots fine, Attaching
grub.cfg that is generated, modified grub.cfg and /etc/fstab.