Microsoft dropped something of a bombshell yesterday at the LinuxWorld Conference and Expo in Boston.

The Redmond giant shook the server virtualisation market with the revelation that it will now provide technical support for Linux running on Virtual Server, and would make Virtual Server 2005 R2 available free.

Zane Adam, director of product marketing in the Windows Server Division at Microsoft, explained that the company will support Linux running as a "guest" in Microsoft Virtual Server 2005 R2 from a technology and support perspective.

"This will help customers safely consolidate their Linux-based applications on Virtual Server," he said.

"With this expanded support, we are providing software that they can install in the Linux guest operating systems to realise significant improvements and usability enhancements with those guests.

"Initially, we are supporting multiple Linux distributions from Red Hat and Novell, two of the most widely used commercial Linux distributions."

Microsoft also announced that Virtual Server 2005 R2 is now available as a no-charge download.

"Combined with the flexible virtualisation licensing now available with Windows Server 2003 R2 Enterprise Edition, this means there is little barrier to adoption for customers who want to realise the benefits of server virtualisation," said Adam.

In a third announcement, Adam claimed that Microsoft is seeing momentum around its Virtual Hard Disk (VHD) format licensing programme. VHD captures the entire virtual machine operating system and the application stack in a single file.

"As a common virtualisation file format, VHD will help provide more seamless manageability, security, reliability and cost-efficiency for customers, and help to ensure a uniform product support system," said Adam.

"We now have more than 45 vendors signed up in this royalty-free licence programme, which is more than double the number we had six months ago."