Getting Started - Docker, The linux container engine
docker.io
docker.io
I understand the "type the correct string and go to the next step" kind of tutorial, but as someone who is used to the Linux shell and had heard about Docker, but never used it, it's a bit frustrating to finish the tutorial and not be able to play around a bit with the "simulator" to test Docker without having to install it.
Anyway, I suppose it serves the purpose of "getting started".
That page looks like this under Ubuntu Chrome: http://i.imgur.com/Vr1y8Cf.png
And indeed in a simple test/development setting, you can use Docker without the overhead of installing supervisord, runit, upstart etc.
But once you're in production, you typically want to combine the two: a process supervisor to manage the boot process of your machine, auto-restart etc. (typically upstart on Ubuntu, systemd on Red Hat 7+, etc.). In this case, the supervisor simply calls out to docker, which "wraps" your application in a way similar to chroot.
I hope this helps.
Personally, I found this tutorial being a bit frustrating due to implementation limits. Particularly, because it's just type-correct-substring instead of achieve-the-result. For example, "docker search tut" fails and pasting text's limited to C-v. (However, I was surprised C-r worked. Neat!)