Read this book to learn the answers to questions like:

• Why do so many problem-solving sites suggest that I repair permissions?
• Why can't I always access my own files when I boot from an external drive?
• What should I do if someone tells me to "set the permissions to -rw-r--r--"?
• What are promiscuous permissions, and should I be informing the vice squad?
• What are access control lists (ACLs), and what's new about them in Snow Leopard?
• What are the default permissions for copied files?
• With the NetInfo database gone, how do I edit account settings such as numeric UID?
• How do I work with account groups from System Preferences?