Before I left, I've set up an old computer with Lubuntu 14.04 32-bit. While trying to set up rtorrent, I did something to lock myself out while following this tutorial.
Normally my computer has one user only, and I login through SSH. However, I added a new user while doing this just like it said and now I can't login as the new user or myself. I do still have a living FTP connection.
How can I restore access to my server?