I am using FreeBSD 6 ... and I use putty to remotely login to FreeBSD ... But the problem is that I can login with all my logins except the root ... when I login through root it gives me an error :

server sshd[500] : error : PAM authentication error for root from backupserver.

What should be the cause ??

That's by design.

You should never log in remotely as root directly. If your password were the slightest bit insecure, you could be open to a brute-force password attack, and your whole system can be compromised.

As an alternative, add your user to the wheel group. That allows you to use the su command to gain root priviledges. Either that, or study up on the sudo command, which gives a finer-grained control on who can do what, and with what priviledges.

Sorry for late reply .. actually I didnt get a chance to get my hands on FreeBSD. But now I've done it ... I added my user to wheel user group and now I can login through root using su command. Thanks for the help. Thread Solved.