I'm a sysadmin/developer/devops-guy, but despite "knowing" Docker I had a lot of fun going through this course, once I'd completed it I found I'd learned a few useful things, and my understanding was much more comprehensive:
My first time doing online-learning, and registering for the university, but now I've done it I'm gonna work my way through a few more of the courses.
(You don't need to register, you can just start reading/completing the exercises, and use the telegraph chat-group for help. Mixture of English and Finnish, if you ask questions in English people will use that happily. You only need register if you want official credits, which might be useful in the future for me, but probably not people outside the country)