Today I experienced a small heart-attack while rebooting a Debian Linux VM.
grub2 told me "no argument specified" after the GRUB-Splashscreen when normally loading the initrd and the kernel.
The solution was as simple as that:
OLD: search --no-floppy --fs-uuid --set 857d5af9-23cd-4d9b-908b-cc075e866758
NEW: search --no-floppy --fs-uuid --set=root 857d5af9-23cd-4d9b-908b-cc075e866758
There must have been some syntax change recently I didn't realize.