Group and file permissions: Linux file sharing

Linux systems have multiple users -- and a permissions system that lets each user share or protect their files. This unique system has some odd twists. For example, did you know that, to rename or remove a file, you need write permission for the directory that the file is in? A thorough understanding of permissions lets you make your system more secure, share data easily with other users, and protect files from accidental changes. Let's look into the basics -- and some dark corners -- of Linux filesystem permissions.