Linux

Linux Basics

In order to become a good ethical hacker or penetration tester, you need to be conversant with
Linux, which is by far one of the most powerful operating systems. Linux is really good for ethical
hacking and penetration testing because it is compatible with a wide variety of related tools and
software, whereas other operating systems such as Mac and Windows support fewer of these software
and tools. In this chapter, I will teach you some of the very basics of operating a Linux OS. If
you are already familiar with Linux basics, you can skip this chapter.

One of the most common questions asked in many forums is “Which Linux distro should I
use?” As there are tons of Linux distros such as Ubuntu, Fedora, Knoppix, and BackTrack you
can use any Linux distro you want as all work in a similar manner. However, I suggest you use
BackTrack if you really wish to dig deeper into this subject because it is all encompassing from a
penetration tester’s perspective.

Major Linux Operating Systems

Before talking about BackTrack, let’s take a look at some of the Linux-based distros that you will
encounter very often:

Redhat Linux—Used mostly for administration purpose.
Debian Linux—Designed for using only in open source software.
Ubuntu Linux—Designed mostly for personal use.
Mac OS X—Used in all Apple computers.
Solaris—Used in many commercial environments.
BackTrack Linux—Used mostly for penetration testing.

 
File Structure inside of Linux

On a Linux system, most everything is a file, and if it is not a file, then it is a process.
Here is a general diagram for file structure in Linux.

Directories—Files that are lists of other files.
Special file—The mechanism used for inout and output. /dev are special files.
Links—A system to make file or directory visible in multiple parts of the systems.
Sockets—A special file type, similar to TCP/IP sockets providing inter-process networking.
Pipes—More or less like sockets; they form a way for process to communicate with each other
with out using network socket.
File types in a long list: