OECS 204 LINUX OPERATING SYSTEM ASSIGNMENT 1 Linux History DOÑA ANA COMMUNITY COLLEGE THE HISTORY OF UNIX AND GNU-LINUX • Developed by Linus Torvalds while he was an undergraduate student • He released it to the world in September 1991 • The name Linux is a combination of Linus and UNIX THE HISTORY OF UNIX AND GNU-LINUX • He immediately made the source code available to others for free • Programmers around the world quickly extended the kernel and developed other tools • The Linux operating system, was developed through the cooperation of numerous people around the world What is “Free” Software • "Free software" is a matter of liberty, not price • To understand the concept, you should think of "free" as in "free speech," not as in "free beer" THE CODE Is FREE • The tradition of free software dates back to the days when UNIX was released to universities at nominal cost • This contributed to its portability and success. • This tradition eventually died as UNIX was commercialized and manufacturers came to regard the source code as proprietary • As each manufacturer tuned UNIX for a specific architecture, the operating system became less portable and too unwieldy for teaching and experimentation THE HERITAGE OF LINUX: UNIX • UNIX system was developed by researchers who needed a set of modern computing tools to help them with their projects • Universities and colleges played a major role in furthering the popularity of the UNIX operating system through the "four-year effect.“ • Schools started using it in their computer science programs, causing the CS students to see its potential • The students became acclimated to this programming environment • When they graduated and went into industry, they expected to work with a similar environment • As more of them worked their way up the ladder, the UNIX operating system found its way into industry GNU Project • Richard Stallman (http://www.stallman.org) announced the GNU Project for creating an operating system, both kernel and system programs • He also presented the GNU Manifesto, which begins as follows: • GNU, which stands for Gnu's Not UNIX, is the name for the complete UNIX-compatible software system which I am writing so that I can give it away free to everyone who can use it. • Some years later, Stallman added a footnote to the preceding sentence when he realized that it was creating confusion: • The wording here was careless. The intention was that nobody would have to pay for *permission* to use the GNU system. GNU Project • In 1991, when Linus Torvalds finished writing the Linux kernel, his friends looked around for free software to finish a UNIX-like system • What they found was the GNU system • The available “free software" added up to a complete system • The GNU Project had been working since 1984 to make a UNIX- like system Obtaining Linux • You can obtain Linux at no cost over the Internet • You can also obtain the GNU code via the U.S. mail at a modest cost for materials and shipping • You can support the Free Software Foundation (www.fsf.org) by buying the same (GNU)code in higher-priced packages • You can also buy commercially packaged releases of Linux that include installation instructions, software, and support GPL License • Linux and GNU software are distributed under the terms of the GPL (GNU General Public License • The GPL says you have the right to copy, modify, and redistribute the code covered by the agreement • When you redistribute the code, however, you must also distribute the same license with the code, thereby making the code and the license inseparable • If you download source code from the Internet for an accounting program that is under the GPL and then modify that code and redistribute an executable version of the program, you must also distribute the modified source code and the GPL agreement with it • Because this arrangement is the reverse of the way a normal copyright works (it gives rights instead of limiting them), it has been termed a copyleft. LINUX Is MORE THAN A KERNEL • Although technically Linux is the name of the kernel, the term Linux has come to mean much more • By itself, a kernel is not of much use, so the Linux kernel is typically packaged with utilities and application programs • Many of the utilities that are distributed with the Linux kernel were written as part of the FSF's GNU Project • Although the FSF prefers to refer to the combination of programs as GNU/Linux, most people simply call it Linux. • Click on this link to listen too Richard Stallman talk about his project: https://www.youtube.com/watch?v=UK52v6bCPvg Distribution • These packages of kernel and programs are distributions of Linux and are referred to simply as distributions or distros • A distribution typically includes word processors, spreadsheets, media players, database applications, and a program to install the distribution • A distribution also includes libraries and utilities from the GNU Project and graphics support from the X Window System OPEN-SOURCE SOFTWARE AND LICENSING • On January 22, 1998, Netscape announced it would make the source code for its next Web browser available for free licensing on the Internet • The month after that, Netscape staffed a project named Mozilla to coordinate the development of the Mozilla Application Suite OSI • Inspired by Netscape's bold move, a group of people got together the next month and held a strategy session that created the term open source • This term provided a label for Netscape's approach and contrasted with the term free software, which was used as a philosophical and political label rather than a pragmatic one • From that session, Eric Raymond and Bruce Perens founded OSI (Open Source Initiative) in late February 1998 to encourage the use of the new term FOSS/FLOSS • FOSS = Free and Open-Source Software • FLOSS (Free/Libre/Open-Source Software • the libre denotes freedom • Free software, the term coined and supported by the Free Software Foundation (FSF), suggests the freedoms it gives its users (as in free speech), whereas open-source software suggests the strengths of the peer-co-peer development model • The terms FOSS and FLOSS incorporate both free software and open-source software and can be used without indicating a preference for either term WHAT Is So GOOD ABOUT LINUX? • In recent years Linux has emerged as a powerful and innovative UNIX work-alike • Its popularity has surpassed that of its UNIX predecessors • Although it mimics UNIX in many ways, the Linux operating system departs from UNIX in several significant ways • The Linux kernel is implemented independently of both BSD and System V • The continuing development of Linux is taking place through the combined efforts of many capable individuals throughout the world • Linux puts the power of UNIX within easy reach of both business and personal computer users • Using the Internet, today's skilled programmers submit additions and improvements to open-source developers such as Linus Torvalds and the GNU Project. POSIX Standards • In 1985, individuals from companies throughout the computer industry joined together to develop the POSIX (Portable Operating System Interface for Computer Environments) standard • POSIX is based largely on the UNIX SVID (System V Interface Definition) • Released in1988, POSIX is a group of IEEE standards that define the API (application programming interface), shell, and utility interfaces for an operating system • With these standards, software developers are able to develop applications that run on all conforming versions of UNIX and Linux type systems Applications • Many applications are available for Linux; both free and commercial • A wide variety of tools is also available, such as: • Graphical, word processing, networking, security, administration, Web server, and many others. • Some large software companies now have on-staff programmers whose job it is to design and code the Linux kernel, GNU, KDE, and other Linux based software • This indicates that Linux is becoming mainstream and is respected as an attractive alternative to other popular operating systems Virtual machines • A virtual machine (VM or guest) appears to the user and to the software running on it as a complete physical machine • It is, however, one of potentially many such VMs running on a single physical machine LINUX Is POPULAR WITH HARDWARE COMPANIES AND DEVELOPERS • Two trends in the computer industry set the stage for the growing popularity of UNIX and Linux: • First, advances in hardware technology created the need for an operating system that could take advantage of available hardware power • PC’s began challenging the large mainframe computers because, in many applications, they could perform the same functions less expensively. • Second, with the cost of hardware continually dropping, hardware manufacturers could no longer afford to develop and support proprietary operating systems LINUX Is PORTABLE • A portable operating system is one that can run on many different machines • More than 95 percent of the Linux operating system is written in the C programming language • Because Linux is portable, it can be adapted (ported) to different machines and can meet special requirements. THE C PROGRAMMING LANGUAGE • Ken Thompson wrote the UNIX operating system in 1969 in PDP-7 assembly language • To make UNIX portable, Thompson developed the B programming language, a machine-independent language, from the BCPL language • Dennis Ritchie developed the C programming language by modifying B and, with Thompson, rewrote UNIX in C in 1973 • Originally, C was touted as a "portable assembler." The revised operating system could be transported more easily to run on other machines. • That development marked the start of C • C can be used to write machine-independent programs • C is a good systems language. • You can write a compiler or an operating system in C LINUX HAS A KERNEL PROGRAMMING INTERFACE • The Linux operating system is a control program for computers • It also has a family of utility programs and a set of tools that allow users to connect and use these utilities to build systems and applications.