Under Linux, access to files and directories is controlled by a
system of permissions. Those permissions define who can see a
file, whether they can modify it in any way, and in the case of
some files, whether the commands within that file (or the file
itself) can be executed. By executed, we mean "can we run that
program?". Let's take a look at permissions and how you you can
work with them. Your introduction is one of the first commands I
told you about, "ls", the program you use to list files. When we
use the 'ls -l' command, we get our first look at Linux
security, this time at the file (or directory) level. Here is an
example of a long 'ls' listing. $ ls -l total 3 drwxr-x--- 5
root system 512 Dec 25 12:01 presents -r-xr--r-- 1 zonthar users
123 Dec 24 09:30 wishlist -rw-rw---- 1 zonthar users 637 Nov 15
09:30 griflong The first entry under the total column shows a
directory (we'll talk about the next nine characters in a
moment). The first character is a 'd' which indicates a
directory. Right at the end