On Thursday, VMware's Chief Technology Officer Mendel Rosenblum told attendees that Linux is an ideal operating system for running virtual machines in the data center of the future. That's because Linux, with its modules surrounding a kernel of key functions, is easily stripped down and specialized for particular applications.

"Linux is a highly customizable operating system. This is a place where Linux will dominate, will shine," he predicted.

A day earlier, Ron Hovsepian, CEO of Novell, the distributor of Suse Linux, said that Linux "will capture 36% of the virtualization market by 2011," citing market research firm IDC as the source of his figures. Linux is typically adopted for its open source code characteristics -- freely available, maintained by a large community, and reliable server functionality. But Rosenblum ignored those qualities and lauded it for its modular design, the ease of adding and subtracting what's known as its tagged software "packages." The ease of add/remove in it make up gives Linux its overall adaptability.

Rosenblum said modern operating systems try to be general purpose managers for all conceivable applications that might run on top of them. As a result, they are large and complex -- a change in one part affects many other parts.

"Even with a huge team of engineers, Microsoft had trouble doing anything" with its Vista release of Windows, dropping several wanted features because of Windows size and complexity, he said. Microsoft and VMware compete on virtualization products. An IDC spokesmen said the same report that gives Linux a 36% share of virtualization software revenues by 2011 says Microsoft will capture 52% of virtualization software revenues in the same timeframe.

Nevertheless, the Linux share reflects an estimated broad use of Linux for virtualization purposes, explained IDC spokesman Michael Shire.

Microsoft charges for each copy of Windows that is used in a virtual machine, along with annual maintenance fees. Linux suppliers, such as Red Hat and Novell, usually sell the operating system on a subscription basis with no upfront license fee. They charge instead for annual support. The virtualization revenues IDC projects for Linux mean that Linux will be running in a large number of virtual machines, and technical support from Red Hat, Novell and other vendors will amount to 36% of total projected virtualization revenues. Novell