No Ethernet

[Moltke]

That post in that link is exactly the same as my problem, but where do i add the

Which one? There are two of them.

And when i do su and enter my password it says su: Authentication failure.

Why do you need su for? As far as I remember root account password is locked by default in Ubuntu and I believe it is too in LL since it's based on it. Sudo command is not enough? Try sudo su and see if that works.