One way to remember these commands without necessarily going "full sysadmin" is to use them on a daily basis. Whether I am developing, managing files, debugging, or really doing anything other than mindlessly browsing the web, I always have at least one (and often many) xterms open. The huge selection of tools and speed of invocation provided by a modern *nix command line is invaluable for many tasks that are not directly related to administrating a system.