I’ve already written about Unix or Linux commands for changing user rights.
This guide will refresh your UNIX or Linux permissions:
Most mortals who deal with *nix systems occasionally get confused about file and directory permissions. Sometimes it's the order of the read, write, and execute bits.
Other times it's the octal stuff, or maybe how to decipher the setuid and sticky bit trickery.
My goal here is for this page to serve as an instant *nix permissions refresher for those who already understand the stuff but get tripped up sometimes on the details. When you forget something, load up the page and there it is. Eventually it'll become second nature and you won't have to come back at all (that came out wrong).
A Unix/Linux Permissions Refresher [dmiessler.com]