RI had a no boot device black screen after switching my laptop back on after several weeks. Following dell support instructions I went to the Bios menu (tapping the F2 key during the initial boot sequence). In the Bios menu, I switched the boot mode from Legacy to UEFI and restarted. I now have a initramfs prompt and after typing reboot, GRUB is displayed and if I choose the top Ubuntu option, I get a kubuntu screen followed by the initramfs prompt again.
ALERT! /dev/disk/by-uuid/e93ad2e1 does not exist. Dropping to a shell!
(initramfs) cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.19.0-80-generic.efi.signed root=UUID=e93ad2e1 ro quiet splash
(initramfs) cat /etc/fstab
cat: can’t open ‘/etc/fstab’: no such file or directory