A specification was started about this problem: https://features.launchpad.net/distros/ubuntu/+spec/no-automatic-root-login-for-grub-recovery Somebody needs to work on it.
-- on fscheck a root shell is presented without password https://launchpad.net/bugs/66001 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
