how to disabling root user

dear all,
pls give the sollution to disable root login from telnet directly.but it should allow while we type su command

On my Ubuntu Linux machine I can do this by editing /etc/securetty and commenting out all entries except for tty1 through tty8.

**EDIT - Sorry, I didn't realise this was in the SCO section, maybe someone should delete my post. Apologies.

For SCO UnixWare 7.1.x, you need to add the following line to /etc/default/login:

CONSOLE=/dev/console

This ensures that root can only login locally from the console. You must 'su' to root via telnet.