How many ways to disable root user login not in GUI as well as CLI mode?
 

For security feature I have to disabled root login (CLI & GUI) in my company, so that how can I disabled it?

Ubuntu has the root account disabled by default and uses sudo; you could use that.
Or edit /etc/passwd, per instructions here.
Since passwd applies for both GUI and CLI, it will disable both.

It's difficult to understand why this is a security feature. Sounds like security by obscurity. What do you want to achieve?

This does not make sense.....do you mean that you want to enable it again?

I want to say delete the root account.


Could make a password that is so long it takes forever to put it in.

How do you intend to do any administrative work? Are you planning on just giving one of the users full sudo capability? Because that seems like a big step backwards as far as security goes.

If you want to disable REMOTE root login, then set
in /etc/ssh/sshd_config.

For local login, as above, disabling it is risky; you might paint yourself into a corner.
Giving full sudo rights to another user a la Ubuntu is non-std.
If you are the Company Admin and you want to stop local users using root, then change the passwd to something only you know & make it strong).
Note that physical access to a box means they could bypass that ...