Metal.SmurfAn insightful primer by Scott and Nate on linux file permissions. For years I erroneously thought 'world' permissions literally meant everyone, which is in fact, not quite correct.
https://www.youtube.com/watch?v=qGfSVUrrTt0&list=PLXJyD2dL4oqeX-C3MvsMUJuEzWM4vLK2C