The pressure on businesses to drag themselves into the information age with the establishment of intranets or company Web sites and databases can cause expensive corporate headaches.

Building a reliable server on which to run e-mail, Web, file transfer protocol, and shared database information is a daunting task. But there is a cost-free solution to the problem.

Linux - a powerful version of the Unix operating system - can be downloaded free from the Internet, and embodies all the features required in a modern environment.

It can be readily customised for individual requirements, and comes complete with the source code, which means problems can be sorted in-house, without having to recruit outside expertise.

When it comes to building a reliable server, the Unix operating system (OS) is regularly called upon to meet the needs of enterprise. OSs civilise a computer's basic behaviour and teach it how to interact with different applications and peripherals.

Most people will have heard of Unix, though very few people actually understand its relevance. It is widely held to be the most influential piece of software ever invented the design of Microsoft's DOS, the most powerful operating system for personal computers, owes a large intellectual debt to Unix. This patriarch of OSs was the foundation for the establishment of the Internet, and the most popular programming language for small computers, C, was developed in conjunction with Unix.

The only snag with Unix is that it is widely viewed as being difficult to use and administer. Commercial Unix solutions can require expensive hardware and support, and they don't always come with the answers to your specific problems.

Windows NT is increasingly being touted as the leading enterprise solution for small to medium organisations. In fact it is quite costly - running at around £600 - and generally involves a commitment to purchase further products from Microsoft.

But there is a cost-free alternative in the shape of Linux, a powerful version of Unix which can be downloaded without payment from the Internet.

It is not designed to handle the requirements of huge corporate enterprises but increasingly it is appealing to small to mediumsized businesses. It can run shared printers, FTP, e-mail, act as a router connection to the Internet and configure a firewall.

And the trend seems to be catching on, as increasingly, free software - like Apache, which is used by more than half of Web servers worldwide - can be loaded on top of Linux for day-today personal computer requirements. Though Linux has been available free since 1991, the takeup by businesses has been slow. The only explanation is an innate suspicion by consumers of anything that is free or even cheap.

"People pay big money for commercial operating systems because they like the security of the backup name and support. Organisations are generally oriented towards buying major brands, and there is a perception if it costs nothing, then it doesn't work," says Mr Barry Redmond, head of electronic engineering at the Dublin Institute of Technology (DIT) on Kevin Street.

Linux is used as a platform in the college to run a Web server which registers around 30,000 hits per week. It is also run separately on another machine as a name and mail server. When Mr Redmond originally went about installing Linux as an experimental Web server he set aside three or four days to complete the task. He completed it in one afternoon.

"You need a high level of technical confidence more than technical competence. Once it is up and running it is very simple to maintain. Unlike Unix itself, there is never any need to restart it - both stable and reliable, it is a very professional piece of software," says Mr Redmond.

Gradient Solutions, which exclusively connects more that 7,000 travel agents worldwide to its infrastructure in Dundrum in Dublin runs more than half its network on Linux.

According to Mr Stuart Coulson, technology director at Gradient, Linux runs faster and more reliably than commercial OSs. By accessing Slackware.org, virtually all the software necessary to run a company's peripherals off one machine can be downloaded.

Some customers can have reservations about running free software on their commercial systems, but Gradient prefers using Linux for its bug-fixing and customising capabilities. He debunks the myth that the absence of official technical back-up is a stumbling block.

"Because Linux is run and maintained by enthusiasts, bugfixes are usually available before any commercial OS. Sometimes a fix can be posted within three or four hours, where the commercial OS could take a couple of weeks," says Mr Coulson. So why is Linux free, when other companies are amassing huge profits by selling their OSs? It basically comes down to one man and the magnanimous spirit of the Internet.

Linux was the brainchild of Linus Torvalds - a computer science student at the University of Helsinki in Finland in 1990. At college he was using expensive Sun Workstation hardware which he wanted to use on his computer at home.

He developed his own version of Unix over the Internet, so by the time the first version came out computer junkies everywhere jumped on it to try and perfect it. In 1993, version 1.0, the first "production" version was released under a free-distribution license.

Today Linux is an international product distributed under the GNU General Public License, meaning the source code must accompany the software. A network of hundreds of volunteers around the world handles development and maintenance.

Though Linux is free, most people choose to pay a minimal amount for a vendor-backed distribution, such as Red Hat, Caldera or Slackware. More often people buy a complete package on CD-ROM, the advantages being easier installation and some level of support. It can also be very time consuming to download Linux straight from the Internet, particularly if access is slow. The cost of a Linux CD-ROM can run anywhere between $3 and $100, depending on the distribution.

Caldera, which has one of the most complete Linux programs, offers a support contract for $1,500 a year or $60 an incident. Walnut Creek offers only installation support, while Red Hat has established a system of support through third parties, whereby they sign up as Linux supporters offering help to the Linux public.

Linux remains at the coalface technologically, because it is constantly honed and updated by enthusiasts. Drivers for new hardware are likely to be available for Linux even before they are available for other versions of Unix, such as Solaris.

Even NASA has used Linux to build supercomputers, rather than invest in hugely expensive machines like the Cray computer. Instead, scientists will buy cheap commodity hardware and use Linux to link them up.

Digital Domain, a movie postproduction company based in LA, recently used Red Hat Linux to render scenes for the new movie Titanic. A network of 200 Alphabased machines was used to speed up rendering times by more than three times.

Some words of warning though. It is generally accepted that Linux assumes a certain knowledge of computers, and Unix in particular. It is not idiot-proof, though companies like Red Hat and Caldera have been doing their best to make it more user friendly. It is not an enterprise-wide operating system either, and even operating on a small scale, applications tend to be geared towards scientific, statistical and engineering use.