ACL: Using Access Control Lists on Linux

Access Control Lists aka ACL's are one of those obscure Linux tools that isn't used every day; and if you find yourself using ACL's every day than you probably have a very complicated Linux environment. A few years ago I had an engineer tell me “Any thing you want to solve with ACL's can be solved with standard unix permissions” and while he may have just been justifying why he didn't know ACL's very well.