Linux Access Control Lists

ACLs are available with the ext3 file system. By default, Red Hat Enterprise Linux 5 sets the capability for ACLs on all the ext3 partitions at install time. What this means is that if you create a new partition that was not in existence at install time and try to use access control lists on it, you can't: you will have to add the mount option ACL in the /etc/fstab file to make that feature available.

Most relevant commands support ACL lists, but some don't; if you're in doubt, you should check the man pages to make sure. "tar", for example, does not support access control lists.