What is it?
A variant of Unix from the open source community, Linux is now offered by almost every hardware and software supplier not intimately tied to Microsoft.
It has become a viable choice for businesses. IBM and HP offer 24x7 Linux helplines, there are specialist Linux support companies, and distributors such as Caldera and Red Hat provide an accountable source.
Nobody knows how many of the world's servers run Linux. Analysts put annual sales at between 9% and 30%. But people get Linux from all kinds of sources and load it on both new and old servers.
You can copy Linux as often as you like onto as many servers as you like - a big attraction at a time when Microsoft is making its licensing more restrictive and expensive.
Where did it originate?
"I'm doing a (free) operating system (just a hobby, won't be big and professional)," wrote Linus Torvalds in 1992, inviting help with the project that was to become Linux. Linux entered the business arena with distributors Red Hat, SuSE and TurboLinux, and joined the mainstream when big guns IBM, HP and Sun adopted it.
What's it for?
The source code is freely available. Although anybody can make any enhancements they like, they must be kept in the public domain. The best enhancements are incorporated into the current version.
What makes it special?
Less crash-prone than Windows, the Linux operating system is free, or very cheap, and is unencumbered by restrictive licensing. It is also a natural partner for the most widely deployed Web server, Apache - another open source product.
Linux champions say its open source nature means bugs and security loopholes are more likely to be detected before deployment, and any that slip through can be fixed more quickly.
How difficult is it?
"It is a fine Unix variant, and Unix people take to it like ducks to water," says Gary Barnett, research director at analyst firm Ovum. With more tools and standardised user interfaces, Linux is becoming easier to use and manage. But it is still more demanding than Windows or Solaris.
Red Hat specifies certain prerequisites for its developer training programme. These include C programming experience, shell scripting in a
Unix environment, and editors such as vi (Virtual Interface) and Emacs (Editor Macros).
Where is it used?
Linux is most successful as a Web server, but it is used in many other applications too. Red Hat has launched secure, high-performance Advanced and Enterprise servers. Customers include AOL Time Warner, Morgan Stanley, Cisco and Amazon.com.
What does it run on?
Linux can run most Unix applications. Emulation products such as VMware Workstation, Win4Lin, Wine and Crossover Office run popular Windows applications such as MS Office on Linux.
Few people know that
A geek - an insulting name which the open source community has proudly adopted - was originally a term used to describe a fairground freakshow performer who bit the heads off live chickens.
What's coming up?
The first Linux handheld computer designed for enterprise applications, Sharp's Zaurus SL.
Hewlett-Packard is to build an 8.3-teraflop Linux supercomputer - the biggest Linux machine so far.
Rates of pay
Now it is mainstream, Linux can be required for almost any IT function in almost any industry sector, and salaries vary accordingly. According to the Computer Weekly/SSP Survey, an office systems manager with Linux will receive between £29,500 and £40,000, a systems auditor can expect £38,000, and a systems developer, depending on experience, will command between £35,000 and £45,000.
Go the traditional route with IBM, Sun, HP, Red Hat et al; look for Linux specialists such as First Alternative; or try the tutorials at the following Web sites.