Manual

1. A bit of history

Linux is an operating system based on UNIX. It is said to be a UNIX-like operating system, as it behaves in a way similar to a UNIX system. In order to study and understand Linux, we must therefore first take a look at UNIX.

UNIX originated from an internal need at AT&T, an American telecommunications company. The goal was to organize data found on various types of supports and on heterogeneous systems using a single system, independent of the equipment. The AT&T team first developed the UNIX tree structure that we know today, and before long, modelled the entire behaviour of a computing machine.

Studying Linux therefore involves the study of a machine model, that is, the UNIX model.

• 1960 - Developed by Ken Thompson, Dennis Ritchie at Brian Kernighan at the AT&T Bell Laboratories.
• 1970 - Commercialization of UNIX.
• 1974 - AT&T gives UNIX source code to the University of California, Berkeley.

The Internet revolution and the development of UNIX in parallel:

• 1962 - Development of the DARPA (Defense Advanced Research Project Agency).
• 1962 - Development of the ARPAnet (Advanced Research Project Agency NETwork).
• 1969 - UNIX – TCP/IP.
• 1974-80 – Creation of the GNU project and of the Free Software Foundation.
• 1980 OpenGroup, X/Open, POSIX, X/Free, GNU, FSF.
• 1991 Start of the Linux Project.

2. Versions and standards

There are other variants of the UNIX operating system. A few of them would be: Berkeley System Distribution (BSD - also known as UNIX Berkeley), FreeBSD, SCO UNIX, SunOS / Solaris, NextStep, NCR, IBM/AIX, Apple Mac OS X, HP-UX.

• UNIX is well-established in the industrial sector, in research and in universities.
• The advent of Intel's 80386 chip allows UNIX to be ported to PCs (MS XENIX).
• First release of Linux in 1991.

3. Linux

Linux, also called GNU/Linux, is free and is one of the most well-known versions of UNIX. Linux is distributed under the GPL (General Public License) and was developed by Linus Torvalds (photo), a Finnish student attending the University of Helsinki at the time. As of today, the development of Linux, and more particularly that of its core, is still being supervised by Linus Torvalds.

Linux proposes a technical approach as opposed to the commercial approach of many proprietary versions of UNIX. The Linux system:

• integrates many standard elements of SYSTEM V,
• is C2-compliant (Orange book, a set of security norms),
• and is free and under GNU/GPL (GNU General Public License).

“Free”, in the Linux and open-source world, is taken in the “Freedom” sense. The Linux source code is free for use by anyone who wishes to, and can be modified and redistributed freely.