Check root= bootarg cat /proc/cmdline
or missing modules, devices: cat /proc/modules ls /dev
ALERT: /dev/disk/by-uuid/3ef7ca00-2842-6900-0000-000002000000 does not exist. Dropping to a shell!
BusyBos v1.1.3 (Debian 1:1.1.3-3ubuntu3) Built-in shell (ash)
Enter 'help' for a list of built-in commands.
/bin/sh: can't access tty; job control turned off
(initramfs)