Users, Groups, and Permissions

• Any file has three permission sets: Owner, Group, World

• Each set has three binary flags: Read, Write, Execute

• Directories are special: without “Execute”, you can't read the contents of a directory

• me@locutus:~$ ls -l /etc/init.d/apache2 -rwxr-xr-x 1 root root 7621 2011-11-07 17:45 /etc/init.d/apache2

• me@locutus:~$ ls -l /etc | grep init.d drwxr-xr-x 2 root root 4096 2012-02-08 14:29 init.d