"As a Linux administrator, you may be called upon to set up a
control system for file access. You probably already know how to
set read, write, and execute permissions on files, and you will
need to make extensive use of that knowledge. But, sometimes,
you'll need more than just these permissions settings to get the
job done. That's where filesystem attributes will come in handy.
You can set different attributes on files in order to gain more
control over how they are accessed.
"There are two slight catches, though. You can only set file
attributes on machines with hard drives that are formatted with
either the ext2 or ext3 filesystems..."