strace is the first thing I skimmed down the thread for. You can learn a lot about how things work (or aren't working) by getting really familiar with an strac

strace is the first thing I skimmed down the thread for. You can learn a lot about how things work (or aren't working) by getting really familiar with an strace. Some of my coworkers give me grief for how easily I jump to "let me see an strace" but it works.