Hopefully this will help some folks out
Apt-get tutorial for beginners.
I would like to add this free source I'm currently using:
Linux Journey - https://linuxjourney.comIt's a lesson based tutorial with exercises presented in a very friendly way.
Not a Cheatsheet but with detailed explanation about the most important Commands - however for German-speaking Readers: Linux-Anwenderhandbuch
It also contains a brief History of UNIX/ Linux in the first Chapter.