Access Control Lists (ACL) is a way to support fine-grained per-user or per-group permissions for files and directories. POSIX-like Access Control Lists are now part of many commercial UNIX systems but with these patches available, the same level of flexibility is available for Linux. Extended Attributes are arbitrary name/value pairs that are associated with files or directories. They can be used to store system objects (e.g. capabilities of executables, Access Control Lists) and user objects (e.g. the character set or mime type of a file). The patches support specific kernel versions and only the ext2 and ext3 filesystems. Filesystems like SGI’s XFS under Linux support extended attributes (meta-data) natively. Other operating systems that have similar meta-data support built-in to their filesystems are Windows2K/XP, BeOS and AtheOS.