Sorry, Unix file security

Thanks

Here are the basics, you may want to check out the "FAQ" section for recommendations on beginners books that will provide a lot more information.

Every file on the system has an "owner" and a "group" that it belongs to. These are stored on disk as integers, and are mapped to human readable names using the /etc/passwd file and /etc/group file. Each file also has a set of permissions controlling who can access it. There are three sets of permissions for each file: user, group, and world (everyone else). For each set there are three (not strictly accurate, but I'm sticking to basics here) attributes that can be set: read permission, write permission, and execute permission. These are displayed when you do a long listing with "ls -l".

example:

$ ls -l test
-rwxrwxr-x 1 foo users 13780 Mar 13 13:18 test

So the permissions on this file grant read, write and execute to the user (foo) and group (users), and read & execute to anyone else.

You modify these file attributes using the "chmod", "chown" and "chgrp" commands. Please refer to the respective man pages for details.