For very long time I have been using linux (fig. 1). Unfortunately, the last 3-4 years I have been using windows or MAC OS as my main desktop operating system due to the fact that in the industry and in most Institutions that I've been, linux never gain as much popularity as a desktop Operating System (OS). In fact, I'm pretty sure that there are many people that have never heard of it, although they might have used it, especially in mobile devices. Fortunately, due to its high reliability, high security and the fact that it's free and open source, linux is very well known in the industry of mobile devices, servers, mainframes and supercomputers [1].

So what is linux?

Linux (pronounced as lee-nuuks) is an open-source unix-like operating system which is in most cases free, even for enterprise solutions [2]. It was created by the Finnish American Linus Torvald in 1991 and was builded on c language [2, 3]. At the beginning it was developed for Intel x86-based personal computers, but currently is being used in servers, mainframe computers, supercomputers and mobile devices. From a technical point of view the linux kernel follows a monolithic architecture making it faster especially for special purpose systems [4]. Finally, the Linux OS comes in a large number of distributions either designed for general use or specialized purposes [5].

I know that there are many terms in this definition that you have never heard of it, such as open-source, unix-like, kernel, distributions and monolithic to name a few. Because the termilogoy of the OS is in general quite difficult, I decided to devide this article into two parts. In the first part I will try to give you an overview of what linux is and how somebody could use it, while in the second part I will try to clarify the previous definition.

I'm qute sure, that everybody have recognized in the previous definition the word free. Linux is not only free but an open source OS. This means than not only you can download it out of charge and have an OS in your computer with similar functionality to Windows or MAC OS, but you can also contribute to its development since its code comes with a free licence [6]. You can even buy a computer without windows installed, saving some money, and install linux afterwards.

The installation procedure is quite straight forward and especially for the average user that wants to use internet and write some documents, linux is the best choise. And if you think that some softwares might not exist in linux, there are many open-source source softwares alternatives to commercial one, such as open office instead of microsoft office, gimp instead of photoshop. Just search in your favorite search engine, such as google or bing, the name of your software with the phrase "open source alternative". I know that all the commercial softwares might be more user friendly and user intuitive, but as I said for the majority of the cases, I would say 90%, you would be happy to work with them.

For more advanced users there is a software called wine though which you can install windows softwares, such as microsoft office and adobe suite [7]. In my humble opinion, although softwares like wine might be quite useful in some cases, if you try to install all your favorite windows softwares in a linux machine you will conclude to have a non-linux computer. Furthermore, because wine is an emulator of windows and not actually windows, you might have many crashes and you will start blaming linux for that. So, if you have so specialized softwares that do not exist in linux it will be better to stay in your favorite OS.

The next thing you might think of, is where you can download linux. The question to that is not that simple because there many, in fact hundrends, different linux OSs, which are called linux distributions [3]. However, if you would like just to check the linux OS in your computer, but you hessitate to change your current OS you might consider using the Knoppix Linux (fig. 3) [8]. The Knoppix linux is a linux distribution which provides the user with a boot CD that runs completely from the CD, without having to install it in your hard disk if you don't want to. The only thing you should do is just download the CD from the Knoppix Linux Boot CD, reboot your computer through your DVD-ROM, and enjoy your new OS. Then if you don't like it then you can just shut down your computer, take out the Boot CD and turn on again your computer with windows untouched.

Now that you might have tried linux, you might want to install it permantely in your computer. The only hurdle to that is to choose the appropriate distro. You will not believe how many distributions exist. SUSE, openSuse, Ubuntu, Kubuntu, Slackware, Knoppix, Fedora, Redhat, Debian, CentOS, Arch Linux, Mageia and Mint Linux are only just some of the more than 300 that exists! If I wanted to write in a piece of paper all of them I would need for sure a lot of ink! I even challenge you to see the graph as indicated in this link. So what is a linux distribution?

Linux distribution (fig. 2-11), or distro, is the linux OS modified in such a way to fit the needs of the end-user [3].

This means that there are many linux OSs specialized in specific purpuses, such as mobile applications, servers and desktop computers. They come most of the times with pre-installed softwares which are in the majority open-source in order to meet the needs of the end user. For instance CentOS is a linux distro specialized in enterprise solutions such as VOIP centers though an open source software called asterisk (similar to services provided by skype or viber), while Ubuntu (fig. 4) is a linux distro specialized in desktop computers that comes with a variety of preinstalled softwares. Even Ubuntu itself has different variants such as Kubuntu (fig. 5), which uses the KDE instead of the default GNOME desktop environment (fig. 4, 6), or Ubuntu Studio which is geared to general multimedia production [9]. There used to be even distros like Damn Vulnerable Linux which was an intentionally vulnerable OS for practice/teaching purposes in regards to Network and Computer Security, or others like Kali linux (fig. 7), or BackTrack linux (fig. 8) which are still active and are used for penetrating and security purposes, i.e. to check whether different systems can be easily hacked or not.

So which linux distro should you install? If you like windows environment and you would like something similar you could download openSuse (fig. 9) or Kubuntu (fig. 5) which are using the KDE desktop environment, while if you just want the most installed and popular linux distribution I would suggest Ubuntu. Especially Ubuntu has many tutorials and forums where you might get easily some advice.

For my case the OSs I have used are mainly openSuse (fig. 9) as desktop linux, CentOS (fig. 11) as web/file server for an enterprise solution, Slackware (fig. 10) and BackTrack linux (fig. 8) for just playing with linux since these distros are considered important for getting deep into the code of linux, Windows as Desktop environment due to some softwares I couldn't find in linux and MacOS for multimedia production.

In case you're interested into learning some more things about linux you could advice some tutorials which are aimed either for novice or more advanced users. Some of which are Getting Started with Linux, Linux Guide, and in