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2.1 OVERVIEW
Linux is a free UNIX clone that was developed by volunteers around the world. Although Linux is almost a decade old, it went largely unnoticed by the general public until a couple of years ago. Since then it has become very popular with individual users, universities and large corporations. For example, IBM has made it a major part of their business strategy for server hardware. Many software companies already offer Linux versions of their software, including products such as Oracle, Labview and MSC Nastran. Other companies have developed embedded applications using Linux. Currently Linux can be found in devices as small as a wristwatch [1] and as large as a Beowulf class supercomputer [2]. The popularity of Linux is based on three factors:
This chapter will present the Linux operating system in general, and its current status in computing.
2.1.1 What is it?
Linux is an open source operating system. It is open because users and developers can use the source code any way they want. This allows anyone to customize it, improve it and add desired features. As a result Linux is dynamic, evolving to respond to the desires and needs of the users. In contrast, closed operating systems are developed by a single corporation using static snapshots of market models and profit driven constraints.
Linux is free. This allows companies to use it without adding cost to products. It also allows people to trade it freely. And, with the profit motive gone, developers have a heightened sense of community interest. The Linux community has developed a tremendous spirit because of these core development concepts.
2.1.2 A (Brief) History
Linux has existed since the early 1990s [3], but it grew out of previous developments in computing [4]. It was originally developed to be a Unix clone that would run on low cost computer hardware. Unix was developed in the 1970s. Through the 1970s and early 1980s it was used on large computers in companies and universities. During this time many refinements and enhancements were made. By the mid 1980s Unix was being used on many lower priced computers. By the end of the 1980s most universities were making use of Unix computers in computer science and engineering programs. This created a wealth of graduates who understood what they could expect from a mature operating system. But, it also created a demand to be able to do high level work at home on low priced machines.
Early in the 1990s Linux started as a project to create a Unix clone that would run on a personal computer. This project gained momentum quickly and by the mid 1990s it was ready for users. The first groups to adopt it were hobbyists, academics and internet services. At this time the general public was generally unaware of Linux but by the end of the 1990s it was beginning to enter the public sphere. By 2000 it had entered the popular press, and it was cited as a major threat to at least one existing operating system vendor. Now, it is available off-the-shelf in software and book stores.
2.1.3 Hardware required and supported
Modern computers have ample power for most computer applications. This is more true for Linux. At present there are versions of linux that will run on any platform from an IBM mainframe computer to a Palm Pilot. The smallest Linux installations can fit on a single floppy disk, and run on a diskless computer with a few MB of memory. On the other end of the spectrum, Linux will run on most high end computer systems. An average user would expect reasonable performance on a computer with an old Pentium 100 processor, 64MB of memory, and 2 GB of disk space. On newer computers the performance of the operating system is extremely fast. The list below gives some idea of the capabilities, but complete lists of supported hardware are available [5].
2.1.4 Applications and uses
By itself an operating system is somewhat useless, software applications are added to give desired functionality. Some of the common applications that a computer might be used for are listed below. Linux will support all of these applications, and more, with the right software [6].
2.1.5 Advantages and Disadvantages
A partial list of advantages and disadvantages is given below. The cost, stability and open nature of the system have been winning over a large number of corporate adopters. But, adoption has been slowed by people who don't understand the nature of free software or have a perception that it is difficult to use. In some cases there are also some software packages that are not available for Linux, and won't run under simulators [22] - the most notable of these applications are first person shooting games.
2.1.6 Getting It
There are multiple distributions of Linux. While these all contain the Linux Kernel, they often include different pieces of software, and installation processes vary somewhat. The basic licensing agreement that Linux is distributed under requires that even if it is sold for a fee, it must be made available at no cost and it may also be copied freely by the user. As a result you can often download these distributions over the network at no cost [12][13]. The total download size can be up to 600MB. An alternative is to buy a distribution (the typical cost is $30) which includes a floppy disk, a CD-ROM and a brief manual. These can be found at any store that sells software. Sometimes the distribution will have a higher cost for `deluxe' versions - this more costly package often includes telephone support.
2.1.7 Distributions
In total there are hundreds of Linux distributions. Many of these are specialized for features such as embedded systems, foreign languages, internet servers and security. The list below is for user-friendly installation and usage. The most successful of these distributions is Redhat. Some distributions, such as Mandrake, are based on the Redhat distribution, but with enhancements.
2.1.8 Installing
Each distribution of Linux will have a slightly different installation procedure, but they all follow the basic steps below. The total time to install Linux will between one to two hours. Users with a high level of knowledge can opt to do advanced setup, and new users will have the option of letting the system suggest installation options.
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