What is it?
Linux is a freeware, Unix-type operating system that is distributed along with its source code so users can make changes and then redistribute it.
There is a strange imbalance in the Linux world. At one end it is dependent on a handful of talented individuals, with constant speculation about overwork, burnout and slowing down of creative effort. At the other end, thousands of the world's best-paid IT staff are promoting and selling it, and repackaging it to meet the demands of corporations and governments.
Meanwhile, the argument over total cost of ownership continues. Linux may be "free", or at least cheaper than Windows Server, but Microsoft has been quick to highlight research that has shown it is much more expensive to run, particularly in staff costs. This summer IBM funded a study which claimed that support and maintenance were cheaper on Linux, and Unix people could easily make the transition.
Where did it originate?
In 1991, University of Helsinki student Linus Torvalds requested help developing a free operating system he described as "just a hobby, won't be big and professional".
What's it for?
Linux is still strongest in the server market. IDC figures published in May put server market growth at 13.5%, with Linux at 31.3%, Windows at 10.7% and Unix at 5%.
Examining IDC's figures, analyst Robin Bloor said, "Linux is gaining credibility in areas of server usage where it was weak; package implementations, database applications, decision support and so on." But he warned that where competition depended on the popularity of packages such as Exchange, Sharepoint and Microsoft Business Solutions, "Linux may never get a grip."
For several years it has been predicted that Linux will break into the desktop market, overtaking Macintosh and making a serious dent in Windows. Analyst firm Gartner said, "Given a greenfield environment, most users could get their work done either on Windows or Linux, Microsoft Office or Openoffice. But the world is not a greenfield environment."
What makes it special?
A huge armoury of freely downloadable utilities and development tools, a large and supportive community to push development and help with problems, a growing range of professional service organisations, and effective management tools. Veritas/ Symantec has brought its storage management products for Linux up to the same standard as those for Solaris and other Unix.
Where is it used?
Most organisations start by adopting Linux as a web server, and for some that is where it remains. But Gartner said, "Linux has moved past the curiosity factor stage and is playing a significant role in datacentre deployments."
How difficult is it to master?
Linux is easier for those from a Unix background rather than a Windows background, though major Linux suppliers such as IBM offer training and tools to help make the transition from Windows easier.
What systems does it run on?
Most hardware, from PDAs and mobile phones to mainframes and supercomputers.
What's coming up?
IBM, Red Hat and Trusted Computer Solutions are working together to improve Linux security, with the US government's requirements in mind.