Linux file permissions

Permissions can be modified using chmod, and permissions are derived from the following a combination of user, group and world permissions:

      u  g  o           u  g  o           u  g  o
0600  rw-------   0400  r--------   0200  -w-------
0660  rw-rw----   0440  r--r-----   0220  -w--w----
0666  rw-rw-rw-   0444  r--r--r--   0222  -w--w--w-

u = User
g = Group
o = All Others

For a full list please see http://www.askapache.com/security/chmod-stat.html#chmod-0-to-7777