File permissions

Linux, like UNIX, is a multi-user system, and as such, it needs to implement various security features to protect against tampering or unauthorised (nay even malicious) access. File permissions ensure that only users that have been explicitly (or implicitly) allowed access can read, write or execute files on a system. they can protect user documents as well as system configuration files, executables, directories, basically anything. Permissions are important, so pay close attention.