The jury is no longer out on Linux. Oracle, Novell and even Microsoft have acknowledged the Penguin as suitable for the enterprise.

Oracle, for instance, has begun actively recommending Linux to customers over all other operating environments, including the Unix flavours and Windows. More worrying for Microsoft is Oracle's claim that its user-developers are moving away from Windows to Linux.

"Since January Oracle has been recommending all customers deploy on Linux," said Mark Jarvis, Oracle chief marketing officer, speaking in London last week. "This is a very strategic decision. The economics of Linux make total sense."

An internal benchmark test running Oracle on Intel, with Linux versus Unix on an equivalent-sized Risc system, showed improved performance for one-sixth the hardware cost, Jarvis said.

Novell, whose Netware operating system once held 70 per cent of the network operating system market, has said it will soon offer key parts of its product portfolio on Linux - accepting that co-existence will not be enough.

Among the hardware vendors, IBM, Hewlett Packard (HP), Sun and Dell endorse Linux. This leaves only Unisys as still wholeheartedly behind Windows, having carved a niche with its Windows-based ES7000 enterprise servers, although that now supports Linux too.

For now there are a couple things slowing Linux adoption: awareness at senior company level and the quality of management tools. When both these issues are addressed, the sheer weight of support should enable the Penguin to go on to own the server market.

Independent software vendors (ISVs) told Oracle that more customer awareness of Linux was needed. So part of Oracle's new Unbreakable Linux Partner Initiative, with $150m (£96m) for ISV migration and support funding, will be used to raise awareness.

Not that Microsoft will roll over and accept defeat. Sources close to the Redmond giant say the company is training 140 of its systems staff on Linux and Java - because it now realises Windows technologies will need to co-exist and interoperate with them in many enterprises.

Oracle claims that a sizeable number of the ISVs that attended a recent Oracle New York event had moved systems from Windows. The company said it will soon provide case studies to illustrate this.

Meanwhile, Merrill Lynch now rates Microsoft shares as 'neutral', citing Linux, supported (especially) by IBM, as a threat.