Introduction to Linux

Before you start

Objectives: learn the history of Linux and the different types of licences.

Prerequisites: no prerequisites.

Key terms: source, licence, software, code, cost, free, minix, gnu, public, artistic, linus, project


Unix

Thompson and Ritchie designed UNIX operating system to be something radically different then what was currently begin used. Because of its availability and portability it caught on really quick. Academic institutions and businesses copied, adopted and modified it. The problem was that AT&T didn’t allow UNIX to be sold at first, but it was allowed to be released as a demo or development environment. About 10 years later, when it really caught on and when a number of people and institutions were using it, AT&T realised that they could profit from this so they decided to start licencing it. In 1979 AT&T introduced their UNIX licence, which was licenced per CPU, and was pretty expensive. Educational institutions could get single CPU licence for 750$. Full commercial licence was about 60000$ per CPU. The problem with licencing in general is that when we buy some software, we really do not own it. We are actually granted a licence to use the software. This licencing move form AT&T caused reactions from some people. One of them was Richard Stallman who grew up in a world of open computer programming. Before AT&T started licencing UNIX, the source code was freely available and customizable. People wrote software and shared it with their friends, who then tweaked it. Stallmans solution to this problem was the Free Software Foundation and the GNU Project. The Free software Foundation was designed to promote open source software, which means that the source code was freely available.

Open Source vs Freeware vs Shareware

The Open Source means that the software is distributed with the source files. Users can modify those source files and then recompile the software. In contrast to Open Source, we have Closed Source software, which is distributed without the source code. Example of Closed Source software is Microsoft Windows. We also have Freeware software which is distributed without cost, but can be open or closed source. Another category is Free Software which means that the software is freely distributable, includes the source code and enables users to modify the software. The catch with the Free Software is that it can be distributed at a cost. In this case the “free” doesn’t mean no cost, it means freedom of use. Shareware is software distributed free of cost on a trial or limited use basis. Users are expected to pay the shareware software if they would like to continue to use it after the trial period or to use it with all features enabled. Another important type of licence is Artistic Licence, which allows users to distribute open source software. The example of an Artistic Licence is GNU General Public Licence.

General Public Licence

To accomplish his idea about open source, Stallman created the GPL (General Public Licence), which protects software while still making the source code available. It is a licence which allows us to publish our software and to protect it legally, but the source code always has to be freely available. That means that we can do whatever we want with the binary format of our software. For example, we can sell binary format of our software, but if we use the GPL licence, the source code of our software has to be freely available.

MINIX

Another person who reacted to AT&T UNIX licencing was Andrew Tanenbaum. He used UNIX to teach his students how to program and use operating systems. When UNIX licencing emerged, it was beyond his budget. Because of that he started to work on his own UNIX clone called MINIX. MINIX had a lot of followers, but there was a limitation on the source code. Unlike the GNU Project, with MINIX we could look at a source code but we could not use it.

Linux

MINIX source code restrictions caused a reaction from the guy named Linus Torwalds. In 1991, Linus wanted to create his own MINIX clone, but completely open source. He described what he wanted to do on Usenet and called anybody willing to help him. From that initial post Linux has grown and now it is the fastest growing operating system in the world. Linus first wanted to call it FREAX, but Torvald’s coworker at the Helsinki University of Technology did not think that “Freax” was a good name. So, he named the project “Linux” without consulting Torvalds.

Remember

Linux emerged from the Unix OS which was created by Ken Thompson and Dennis Ritchie. After the AT&T decided to licence UNIX, Richard Stallman founded the Free Software Foundation and the GNU Project. The Open Source means that the software is distributed with the source files. Freeware is distributed without cost, but can be open or closed source. Free Software means that the software is freely distributable, includes the source code and enables users to modify the software, but it doesn’t mean that it is distributed without cost. Shareware is software distributed free of cost on a trial or limited use basis. Artistic Licence allows users to distribute open source software. The example of an Artistic Licence is GNU General Public Licence. When we use GPL the source code always has to be freely available. Andrew Tanenbaum created MINIX and denied the use of its source code. Linus Torvalds created Linux which is licenced under GNU General Public Licence.

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