Consider the implications of enabling the root account, and then proceed with:
user@ubuntu:~$ sudo passwd root
To disable the root account again, use the following command:
user@ubuntu:~$ sudo passwd -l root
Consider the implications of enabling the root account, and then proceed with:
user@ubuntu:~$ sudo passwd root
To disable the root account again, use the following command:
user@ubuntu:~$ sudo passwd -l root