Log-in as root on Linux Terminal

I am going to show you three most used methods to log-in as root.

First way :
If you have sudo privileges as a user, you can use following command to log-in as root on terminal.

$ sudo -i

It asks for your (user's) password. After enter your password, you can log-in as root on terminal.

Second way :

$ su -
or
$ su - root

It asks for root's password. If you know root's password, you can log-in as root.

Third way:
You can log-in as root using secure shell (ssh)

$ ssh ip-of-the-server

If client and server are two different systems, the first two methods do not work to log-in as root on server. Only third method will work.

If client and server are in same system (root and users are in same system) , the first two methods do not require internet to log-in as root on terminal.

Third method requires internet to log-in as root on terminal.