Enable root user login in ubuntu linux

FREQUENTLY ASKED QUESTIONS (Linux)
Q: How to enable root user account in Ubuntu linux?

By default root user account is disabled in ubuntu linux. Actually this is due to no password is set for root user. And you will get an authentication error message like

su: Authentication failure


Set password for root user

user@ubuntu:~$ sudo passwd root
Enter new UNIX passwd:
Retype new UNIX passwd:
passwd: password updated successfully


Now you can switch to root user
user@ubuntu:~$ su root
Passwd:
root@ubuntu:~$

LABELS: Debian, FAQ, How-To, linux, Ubuntu