Q. How do I telnet as the root user?
A. This is really a bad idea as telnet is insecure, because passwords are sent as clear text format. Instead, you should use SSH for connections. I suggest that you use SSH to connect to a system instead of Telnet for security purposes. By default, for security purposes, the root user can not telnet. However, here is method in case you need root access via telnet:
Edit /etc/pam.d/login and /etc/pam.d/remote files using a text editor such as vi. Find the line that read as follows:
auth required pam_securetty.so
Comment it out by prefixing # symbol:
#auth required pam_securetty.so
Save and close the file. Now, you should be able to telnet to your system as the root user.