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Have you ever wondered where your user accounts or group file are? How do you install X? What's the relationship to BSD? How do you set up an account or group with particular uid or gid? In short, what are the little differences and how do you cope as a Unix or Linux user moving to OS X?

This book is the answer. It describes features which in fact are the differences that a Unix user would notice. If you're from a Unix background, this'll make the peace with OS X.