Login as "Su" in new ubuntu machines: you are not in sudoer list

While working on UBUNTU  your may incur in a situation where you need to login as root to execute some task.  When you login as sudo you may get error like: "you are not sudoer list". This ideally due to reason  that when you are trying to log for first time, root as a user is not enabled. Do make root as user ans to enable logging as root.  One has to activate root account in new UBUNTU  machine it is not activated by default. 

Execute command to activate root and set password

sudo passwd root

Once password setting successful then one can go ahead to login a root by executing command below. 

su root