1   BASICS OF LINUX

1.1 Why Linux?

There are several reasons why Linux is such a widely used operating
system.

1.1.1 I's free (as in beer)

Linux is free to download, install and use. This is especially desirable
from a a hobbyist viewpoint since there are no software consts involved.
Most Linux distributions (a term which we will explain below) are free to
use, however there exist some paid distributions. These are generally so
called enterprise distributions which include a maintenance contract and a
license fee. The most well known enterprise distribution is Red Hat Linux,
although there exists a free version of it, called Fedora Linux.

1.1.2 It's free (as in speech)

This type of freedom is of ideological nature: the idea of free software
(sometimes called open source, but that term is often misleading) is that
anyone should be allowed to use, inspect, modify and redistribute
programs. The importance of this ideological freedom is a matter of
personal taste, while some people refuse to use any non-free software at
all, most are not so fanatical. Of course most normal people do not even
know what free software even means.

A highly visible figure in the free software community is Richard Stallman
(1953-) the president of the Free Software Foundation and a profilic
privacy activist. See http://stallman.org for more infomation.


1.1.2 Technical reasons for using Linux

Linux is very flexible and various versions of it can be (and have been)
created for various use-cases. It is possible to use Linux for virtually
any computing task, ranging from digital doorbells to super computing.
This is possible because of the high scalability of the Linux kernel (a
term which will be explained below): it is possible to create a Linux
implementation as small as 10 MB, but it is equally possible to use 2048
processor cores simultaneously.

Linux is also the most commonly used operating system in the world, due to
the approximate 1.3 billion Android devices in use worldwide.


1.2 The most fundamental difference between Linux and Windows

All of the matters discussed above are quite theoretical and do not impact
the day to day use of a coputer system. Additionally while most students
taking this course today are reasonably well-versed in using computers
(this was not the case 20 years ago) the operating system they are most
likely to have used in the past is Microsoft Windows.

Despite the title of this section the difference described here is not
necessarily the *most* fundamental difference, but it is of great
importance when it comes to systems administration, the subject of this
course. This difference is, that generally on Linux systems *software is
installed from a central repository*. The benefits of this arrangement are
manifold, including

* program installation is easy (there is no need to search for downloads
 on the internet)
* programs are easy to update and they can be kept up-to-date easily
* accidentally installing malware is difficult

Of course it is still possible to install software manually, but it
should generally be avoided.


1.3 Linux distributions

We already mentioned two Linux distributions above, namely Red Hat and
Fedora Linux. We will now explain, what is meant by the word distribution.

Linux on its own is only a core of the operating system, called the
kernel, which, on its own, cannot be used for any computing. What is
needed are software or programs, such as sytem utilities. A combination of
the Linux kernel and some set of software is called a distribution or
distro. There are countless of Linux distributions with various
differences in the software selection, but all distros require some set of
utility programs.

The most common set of utility programs, software that is necessary for
operating the computer, are the GNU coreutils which form an integral part
of the vast majority of Linux distros. This is the reasong you sometimes
see the term 'GNU/Linux'.

Some popular Linux-distributions

* Debian: a general use distro, calls itself 'The Universal Operating
 System'.
* Ubuntu: a distro aimed at desktop users, various variants exist,
 based in Debian.
* Fedora: as mentioned above, Fedora is the free version of Red Hat.
* Gentoo: a distro for intermediate and advanced users, highly
 customisable
* Arch Linux: another highly customisable distro, but different
 in philosophy to Gentoo.

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