Why can't Ubuntu 16.04 LTS shut down?
update 2016/07/01 6pm: SOLVED. Details here (but DO read anyway the whole post, because the cause of this problem on your computer may still be one of those below!)
update 2016/07/01 6pm: SOLVED. Details here (but DO read anyway the whole post, because the cause of this problem on your computer may still be one of those below!)