Ubuntu Linux distribution, by default, disables the root account. To run a command with root privileges, sudo has to be used before the command.

During the Ubuntu installation, you will never be asked to enter the root password. If you view the /etc/shadow file, you will notice that the encrypted password (2nd) field for root is usually marked with ‘!’, meaning that it is inactive.

ibrahim@anfield:~$ sudo cat /etc/shadow | grep '^root'
[sudo] password for ibrahim:
root:!:14239:0:99999:7:::

If you want to enable the root account, enter the following:

ibrahim@anfield:~$ sudo passwd
[sudo] password for ibrahim:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

You should now be able to login using the root account.

If you want to disable the root account, lock the root account by using the following command:

ibrahim@anfield:~$ sudo passwd -l root
[sudo] password for ibrahim:
Password changed.