I just got my system to boot up (Scientific Linux), but at the login screen I can't login as root. It doesn't even ask for a password, just says Login incorrect. So what I see is: localhost login: rootlogin incorrectThen: login: rootLogin incorrectWhat did I break this time? I was messing around with essential filesystem files a lot, namely /bin and /sbin. 
System booted up, but can't login as root
login;root