As everyone knows,ubuntu user password can be easily reset from the recovery mode in Grub menu, it allows to access the root console without any password to enter or something like that.It’s unsafe,I think it would be safe if there’s a password to access the root console.
If you enable your ubuntu root password,and there will ask the password to access the root console.
To enable root password:
sudo passwd root
enter new password and again to confirm.
Now,you need to enter this password to access root console from recovery mode.
To disable root password:
sudo passwd -l root