During your career, you will invariably come across multiple operating systems regardless of your job role. Only a handful of operating systems dominate the IT world, and Linux is definitely part of that group. If you never had the opportunity to work with Linux, now is the perfect time to do so. There are many wireless security tools available for Linux that simply do not run on Windows or the Mac OS. The Linux operating system not only makes a perfect desktop OS for wireless users, but is also a dominant player in the server market. Familiarizing yourself with Linux will prove to be a huge benefit to you in your career.

All of the attack tools covered in Chapters 4 and 5 come preinstalled on BackTrack. Some of the tools of defense covered in Chapter 6 come preinstalled on the BackTrack distribution of Linux. At the time of this writing, BackTrack version 5 R1 is currently offered. BackTrack can be run on both 32-bit and 64-bit Intel computers.

You can download the BackTrack operating system from the BackTrack download page (http://www.backtrack-linux.org/downloads/). On the download page, you may be prompted to register. If you wish to give your e-mail address, feel free to do so; however, it’s not necessary.

As an alternative to burning a bootable DVD, you can use a program called UNetbootin to extract the ISO file to a USB drive and make the drive bootable (see Figure A-2). To create a bootable Linux USB drive, download UNetbootin from http://unetbootin.sourceforge.net. Click the large Download button for the operating system you’ll be running UNetbootin from.

Booting to your new BackTrack DVD or USB drive is very straightforward. When you first boot up, you’ll see a boot prompt similar to Figure A-3. You can simply press ENTER at this screen to see the boot selection menu, shown in Figure A-4.

The Linux interface is very intuitive, and in very little time you’ll be moving around like a pro. The bar at the bottom of the screen shows you all your open windows, very much like the taskbar in Windows. These bars are referred to as panels in Gnome. Unlike Windows, the button at the bottom left is not the Start button; instead, it minimizes all the currently open windows (very handy). Also, you’ll notice four squares along the right side of the same bar. These represent virtual desktops, which keep your open windows separate. This can be extremely handy when you have many windows open. You can open windows designated for a specific task on one desktop and then switch through the other desktops by clicking the corresponding icons in the bottom right.

Historically, people think of Linux as being a somewhat difficult operating system to use, partly because it’s command line centric. In the past it was true that the graphical environments weren’t half as intuitive as they are today; however, most of the power of Linux comes from the fact that you can perform any task you need right from the command line. This also means that every task is also scriptable, making common tasks much, much faster.

In Windows, you’re used to running cmd.exe if you want to use command-line tools. In Linux, you actually have a few options for command-line interfaces. At the most basic level, most shells are nearly the same. The only time you see a real difference is when you start creating scripts for different shells. We’ll cover scripting more in depth shortly.

Running a command from a shell is extremely easy—just type the command. You need to be aware of the PATH variable, which tells the shell which folders to look in for the programs you’re trying to run. In the bash shell, your path is configured with the $PATH variable. To view your current path, simply type echo $PATH (note that variables are case sensitive).

Obtaining help and additional information on Linux programs and systems is extremely easy to do. Beside the usual Internet resources, such as forums and websites, you have a few built-in options for obtaining help. The three most helpful commands for obtaining help for a known program are man, info, and help. The man command stands for manual, and you simply provide the name of the program as the argument. For example, to see the manual page for the nslookup command, you would type the following:

The Linux file system is very straightforward, and in time you’ll find it much easier to use than the Windows file system. In Windows, you’re probably used to the C drive being your root partition; in Linux, the root partition is referred to by a single forward slash. Everything, including other drives, are mounted somewhere under the root folder.

BackTrack is based on the Debian distribution of Linux, which means the core system for installing software is the apt group of tools. It couldn’t be any easier to install software on a Debian-based operating system. You can search for a program, and once you’ve identified the name of the package, you simply run the apt program, which automatically downloads the program, along with any necessary files from a list of defined (and approved) servers, and installs it on your system.

Users and groups are created and managed a little differently than in Windows systems. User accounts are stored in the /etc/passwd file (called the password file). The password file is a text-based file with each account on a separate line. Let’s take a look at a few of the entries in the passwd file (see Figure A-8).

Linux is an extremely network-centric operating system. This is great news for you, given that you’re reading a book on networking! Numerous built-in commands and default programs are installed to perform a myriad of networking tasks, including the ability to script every network configuration you can think of.

Linux file permissions are very different from Windows file permissions. This can be a little tricky for new comers, but it’s easy once you get used to it. To view the permissions for a file or directory, simply use the –l argument for ls. Figure A-15 shows a directory with two results.

Scripts are extremely easy to create to perform even very complicated tasks. The most basic scripts use the native shell of choice; however, more robust languages such as Perl exist to handle more advanced tasks. Using scripts, you can call any external program by simply typing it exactly as you normally would, with all the same arguments.

You’re now armed with enough knowledge to start using Linux as a desktop operating system with the details in this appendix. From connecting to and configuring network settings, to adding new user accounts and creating scripts to perform common tasks quickly, you’ll find you can easily perform most of the tasks you’re familiar with in the Windows operating system. Most operating systems include many configuration options—enough to fill entire books—and Linux is no exception. If you plan on making Linux your OS of choice, be sure to check out Linux: The Complete Reference, Sixth Edition, by Richard Petersen (McGraw-Hill, 2007), or Linux Administration: A Beginner's Guide, Sixth Edition, by Wale Soyinka (McGraw-Hill, 2012).