Don't feel too bad about it. Many of those questions are arcane/trivia rather than practical day to day knowledge you must know. Don't get me wrong, it's import

Don't feel too bad about it. Many of those questions are arcane/trivia rather than practical day to day knowledge you must know. Don't get me wrong, it's important to understand concepts (like the encryption question they asked), but knowing off the top of your head how to rm a file named "-f" is not important, but knowing how to figure out how to unlink it is.