Security is a big part of filesystems.

But you can’t have a secure filesystem if you don’t understand how it works.

This is one thing you’re bound to come up against when programming. Just like when you come home and need to unlock your house door. If you forget your key, you get locked out. The types of security problems you’ll be likely to face as a programmer are not usually the type where you forget the key. You’ll be more likely to face issues where you have to manipulate the locks, or pass your identity to other parts of your program, or even take on a different identity for a while.

Let’s say you do forget your house keys for a moment. After calling a relative with spare set of keys or the locksmith, you might be interested in things you can do to prevent this from happening again.

One solution is to just stop locking your door. Or hang the key from a chain next to the door on the outside so that anybody can use it. Would you consider doing this? Chances are, you want to keep your locks.

This episode will explain how traditional file system security works for Unix, or Linux, or Mac computers. They all follow a similar design. These operating systems could have another security system depending on the version. I’ll describe that system in another episode.