users - How to enable root login?

I would like to enable the root account on my Ubuntu installation.

I realize the security implications of this.

While it's possible to do, it is not recommended.

To actually enable root logins first you have to set a password for the root account and then unlock the locked root account. If you don't set a password for the root account the passwd command will return

passwd: unlocking the password would result in a passwordless account.  

So, first execute in a terminal

sudo passwd root

you will be prompted for a new Unix password. Write it twice (second for confirmation).

Then execute

sudo passwd -u root 

to unlock the account. This should return

passwd: password expiry information changed

If you want to disable root account in Ubuntu you need to lock the root account by using the following command sudo passwd -l root

If you want to work on a root console you can also use sudo -i.

Only do this if you know what you are doing. More information on why to stay with sudo here

pkexec gnome-terminal will open a terminal with a root prompt.

passwd root will allow you to create a password for root.

Note: Running users-admin with elevated privileges no longer works because of a bug that is marked as "Won't Fix" for security reasons. See https://bugs.launchpad.net/ubuntu/+source/gnome-system-tools/+bug/685215 for an explanation.

pkexec users-admin will open the users screen: