Unix is one of the most popular operating systemsworldwide because of its large support base and distribution. It wasoriginally developed as a multitasking system for minicomputers andmainframes in the mid-1970s. It has since grown to become one ofthe most widely used operating systems anywhere, despite its sometimesconfusing interface and lack of central standardization.
The real reason for Unix’s popularity? Many hackersfeel that Unix is the Right Thing—the OneTrue Operating System. Hence, the development of Linux by an expandinggroup of Unix hackers who want to get their handsdirty with their own system.
Versions of Unix exist for manysystems, ranging from personal computers to supercomputers suchas the Cray Y-MP. Most versions ofUnix for personal computers are quite expensive andcumbersome. At the time of this writing, a one-machine version ofAT&T’s System V for the 386 runs at about $US1500.
Linux is a freely distributable version of Unix,originally developed by Linus Torvalds, who began work on Linuxin 1991 as a student at the University of Helsinki in Finland.Linus now works for Transmeta Corporation, a start-up in Santa Clara,California, and continues to maintain theLinux kernel, that is, the lowest-level corecomponent of the operating system.
Linus released the initial version of Linux for free on the Internet,inadvertently spawning one of the largest software-development phenomenaof all time. Today, Linux is authored and maintained by a group of severalthousand (if not more) developers loosely collaborating across the Internet.Companies have sprung up to provide Linux support, to package it intoeasy-to-install distributions, and to sell workstations pre-installed withthe Linux software. In March 1999, the first Linux World Expo trade showwas held in San Jose, California, with reportedly well over 12,000people in attendance.Most estimates place the number of Linux users worldwide somewhere around the 10 million mark (and we expect this number will look small by the timeyou read this).
Inspired by Andrew Tanenbaum’s Minix operating system (anotherfree Unix for PCs—albeit a very simple one), Linux beganas a class project in which Linus wanted to build a simpleUnix system that could run on a 386-based PC.The firstdiscussions about Linux were on the Usenet newsgroup comp.os.minix. These discussions wereconcerned mostly with the development of a small, academicUnix system for Minix users who wanted more.
The very early development of Linux dealt mostly with thetask-switching features of the 80386 protected-mode interface, all writtenin assembly code. Linus writes:
After that it was plain sailing: hairy coding still, but I had somedevices, and debugging was easier. I started using C at this stage,and it certainly speeds up development. This is also when I start toget serious about my megalomaniac ideas to make “a better Minixthan Minix.” I was hoping I’d be able to recompilegcc under Linux some day ...
Two months for basic setup, but then only slightly longer until I hada disk driver (seriously buggy, but it happened to work on my machine)and a small filesystem. That was about when I made 0.01 available[around late August of 1991]: it wasn’t pretty, it had no floppydriver, and it couldn’t do much anything. I don’t think anybody evercompiled that version. But by then I was hooked, and didn’t want tostop until I could chuck out Minix.
No announcement was ever made for Linux Version 0.01. The 0.01 sourcesweren’t even executable: they contained only the bare rudiments of thekernel source and assumed that you had access to a Minix machine tocompile and play with them.
On October 5, 1991, Linus announced the first “official”version of Linux, version 0.02. At this point, Linus was able to runbash (the GNU Bourne AgainShell) and gcc (the GNU Ccompiler), but not much else was working. Again, this wasintended as a hacker’s system. The primary focus was kerneldevelopment; none of the issues of user support, documentation,distribution, and so on had even been addressed. Today, the situationis quite different—the real excitement in the Linux worlddeals with graphical user environments, easy-to-installdistribution packages, and high-level applications such as graphicsutilities and productivity suites.
Linus wrote in comp.os.minix:
Do you pine for the nice days of Minix-1.1, when men were men andwrote their own device drivers? Are you without a nice project andjust dying to cut your teeth on an OS you can try to modify for yourneeds? Are you finding it frustrating when everything works on Minix?No more all-nighters to get a nifty program working? Then this postmight be just for you.
As I mentioned a month ago, I’m working on a free version of aMinix-lookalike for AT-386 computers. It has finally reached thestage where it’s even usable (though may not be depending on what youwant), and I am willing to put out the sources for wider distribution.It’s just version 0.02 ... but I’ve successfully runbash, gcc,GNU make, GNUsed, compress, etc. under it.
After Version 0.03, Linus bumped the version number up to 0.10, asmore people started to work on the system. After several furtherrevisions, Linus increased the version number to 0.95, to reflect hisexpectation that the system was ready for an “official”release very soon. (Generally, software is not assigned the versionnumber 1.0 until it’s theoretically complete or bug-free.) This was inMarch 1992. Almost a year and a half later, in late December 1993, the Linux kernel was still at Version0.99.pl14—asymptotically approaching 1.0. Version 1.0 appeared in March1994. As of the time of this writing (March 1999), the current kernelversion is 2.2.6, while the 2.3 kernel versions are being concurrentlydeveloped. (We’ll explain the Linux versioning conventions in detaillater.)
Linux could not have come into being without theGNU tools created by the Free Software Foundation.Their gcc compiler, which we’ll discuss in Chapter 13 gave life to Linus Torvalds’s code. GNUtools have been intertwined with the development of Linux from thebeginning. Because of the critical contributions of these tools, theFree Software Foundation even requests that distributions of Linuxwith accompanying utilities be called GNU/Linux.
Berkeley Unix (BSD) has alsoplayed an important role in Linux—not so much in its creation,but in providing the tools that make it popular. Most of theutilities that come with Linux distributions are ported fromBSD. Networking daemons and utilities areparticularly important. The kernel networking code for Linux wasdeveloped from the ground up (two or three times, in fact), but thedaemons and utilities are vintage BSD.
Today, Linux is a complete Unix clone, capable ofrunning the X Window System, TCP/IP, Emacs, Web,mail and news software, you name it. Almostall major free software packages have been ported to Linux, andcommercial software is becoming available. In fact, many developersstart by writing applications for Linux, and port them to other Unixsystems later. More hardware issupported than in original versions of the kernel. Many people haveexecuted benchmarks on Linux systems and found them to befaster than workstations from Sun Microsystems and Compaq, and Linuxperforms better than or as well as Windows 98 and Windows NT on a wide range ofbenchmarks.Who would have ever guessed that this“little” Unix clone would have grown upto take on the entire world of personal and server computing?
