The fisrt thing I do when starting whith a new group of students is to have a relaxed conversation with all of them tring to make it sound and feel as casual as possible but always staing in topic, this is being helping me to identify the base knowledge of my students as well as getting them to relax in such an abstract topic (Linux OS), also they have the opportunity to get to know me better and to take the rest of the class with interest as we go on some relevant examples an something they don't know yet.