Linux Closely Resembles Un

Linux is often called Unix-like,a Unix clone, or an operating system based on Unix. Such descriptions are accurate but not very illuminating if you’ve never used Unix. Let me remedy that.

Unixhas ancient roots. In 1964, MIT, General Electric, and Bell Labs (then a division of AT&T) collaborated on an operating system called theMultiplexed Information and Computing System, or MULTICS. The MULTICS project, I’m sorry to say, was a disaster. It was large, unwieldy, and buggy.

Despite that early failure, good things emerged from the MULTICS project. Ken Thompson, a programmer from Bell Labs, felt that he could do better. In 1969, with assistance from fellow programmers Dennis Ritchie and Joseph Ossanna, Thompson did just that.

Some signs of the times: America was at war in Vietnam, the number-one hit single was Marvin Gaye’s “I Heard It Through the Grapevine,” and if you were cool, you were driving a Dodge Charger. It was against this backdrop that Thompson did his work.

Thompson’s early Unix was shaky, but that quickly changed. He rewrote Unix in the C pro- gramming language a year later. The result was a quicker, more stable operating system that was both portable and easily maintained.

What happened next was critical. In the early 1970s, Unix was distributed to universities. There, students and educators alike found Unix to be practical, versatile, and relatively easy to use. Unix was therefore incorporated into the computer science curriculum at many universi- ties. As a result, a generation of computer science graduates acquired Unix experience. When they later took that experience to the marketplace, they brought Unix to the mainstream. However, the events that would ultimately make Unix an immensely popular network operating system occurred elsewhere. Around the same time, the U.S. government was working on an internetwork for wartime communication. This network was designed to be impervious to a Soviet nuclear first strike. The problem was this: Although the government had a suitable trans- mission medium, the telephone system, it had no operating system to match. Enter Unix.

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In all fairness to Linux, it should be mentioned that the best NT/2000 administrators also use the command line. The difference between administering Linux/Unix and Windows is mainly one of perception. The assumption is made that you can point and click your way to every- thing you’d ever want to do in Windows, but experienced administrators will tell you other- wise. Linux’s GUI administration tools are often as good as or even surpass their Windows counterparts, but you’ll still need the command line to fine-tune your settings.

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Internetwork engineers chose Unix based on several factors. By then, roughly 1974, Unix already had powerful networking capabilities. For example, thanks to Ray Tomlinson of Bolt, Beranek, and Newman, Unix had electronic mail. Other network protocols would follow, and by 1978, Unix was jam-packed with networking software. The U.S. government got its inter- network after all, which we now call the Internet, and Unix became a phenomenon.

So, Unix is the operating system of yore that was used to create the Internet. Linux shares a common lineage and many characteristics with Unix. For example:

• Much of Linux is also written in C.

• Linux supportspreemptive multitasking, or the capability to handle multiple processes simultaneously. Using Linux, you can simultaneously compile a program, download e- mail, and play solitaire. The system divides up the processor time automatically, so each program can continue to run in the background.

• Linux supports multiuser sessions. Multiple users can log in to Linux simultaneously (and during these sessions, they can also multitask).

• Linux offers a hierarchical file system. Its top-level directory holds subdirectories that branch out to even further subdirectories. Together, these subdirectories form a tree struc- ture. Multiple drives show up within the same tree, rather than as separate entities, as in Windows and Mac OS.

• Linux’sgraphical user interface (GUI)is MIT’s X Window System, or X.

• Linux offers extensive network functionality, supporting most internetworking protocols and services.

Finally, many Unix applications have been ported to Linux, or require no porting at all. Thus, Linux has a pronounced Unix-like look and feel.

In these respects, Linux is very much like Unix. Indeed, Linux so closely resembles Unix that casual users could confuse the two. They shouldn’t. Beyond these similarities, Linux and Unix part ways when it comes to the philosophy behind their development.

For example, Unix evolved into a mostly academic variation (BSD), and a commercial operat- ing system (System V) that, for many years, ran on expensive proprietary hardware. Linux runs on almost anything, including

• Advanced Micro Devices and Cyrix processors • Digital Alpha processors

• Intel 80386, 80486, and Pentium family of processors • Motorola/IBM PowerPC processors

• Sparc processors Linux Security Basics

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Also, Unix licensing can be quite restrictive. Developers must often pay hefty fees for indus- try-standard programming libraries (nearly $17,000 for a full Motif ensemble). As discussed above, Linux imposes no such restrictions.

Finally, there is one major difference between Unix and Linux. Unix vendors provide technical support, but unless you purchase a commercial boxed distribution, Linux vendors don’t (although that’s rapidly changing). Linux was developed by freelance and independent pro- grammers, and in large part continues to be. This brings us to the next issue:Where did Linux come from?

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