Here I sum up how to configure a VPS (virtual private server) running Ubuntu GNU/Linux. I tried it with Digital Ocean, but it must be the same with others too, like Linode, etc.
The original version of these notes was written for Ubuntu 14.04, but then the notes were updated for Ubuntu 16.04. Both versions are available:
If you find a mistake or you have an idea how to extend the notes, let me know (indicate it as an issue).