Having had this netbook running ubuntu natty for a while, and having experienced the pains of not knowing how to do x, y, or z without fumbling about blindly in a maze alternating command line with google searches for “how to…” or “linux command reference kill,” I am contemplating starting a command-a-day series. My goal would be to learn–not merely to be able to do after having looked up–a good selection of the most important active commands, especially for dealing with wonky programs running on the local machine and for manipulating files/directories both on the server and on the local host, and downloading/installing/running programs from the command line. Also searching: grep confuses the heck out of me! At any rate, I could use your help. What, to your mind, are the most important (and useful, for a beginner) commands to learn? What about the most useful delimiters or modifiers? What should a beginner not mess with until a basic sense of the command structures has been grasped?