Can't sudo after removing password from administrator account

Question

I'm using Ubuntu 13.10 64bit. In the "System Settings"->"User Accounts" I chose the "Login without a password". This was my only administrator account, so according to this answer, I encountered bug #1168749, meaning I can't authenticate, not in the terminal and not in the GUI. I tried all of these answers:

• https://askubuntu.com/a/152617
• https://askubuntu.com/a/70445
• https://askubuntu.com/a/136537
• http://www.psychocats.net/ubuntu/fixsudo
• https://askubuntu.com/a/194760/252848
• https://askubuntu.com/a/441575/252848

After the first two I was again able to authenticate in the GUI, but still can't sudo in the terminal after trying all these answers and solutions.. Anyone knows how to fix this bug?

edit

Actually I was wrong, I can sudo (silly mistake, my bad). I just kept trying to enter su and it said:

su: Authentication failure

Answer 1

The behaviour you're describing is normal, because the root account is locked by default in Ubuntu. If you need an interactive root shell you should use sudo -i instead of su

For further information, see the discussion at RootSudo