Recently I faced a huge issues in my production environment ,where ppl try to login as root to system which made system more unstable(Yes I know its in mess- super democracy server). As you know Ubuntu came with ‘Sudo’ concept which gives all the privilege’s that you want in systems. There for don not allow root user in your system especially in production. More details can be found in : https://help.ubuntu.com/community/RootSudo
Two steps to block any root logins :
1. Disable Root user :
sudo passwd -dl root
2. Disable root login in ssh config:
And restart sshd -- > /etc/init.d/sshd restart
BTWAY: I was able to recover lost root password from a linux machine. Will update on that in future release .