Fedora 4 - the first major update to Red Hat's free Linux distribution for seven months - will be launched on 13 June.

Fedora Core 4 will be the first release to include support for the Xen virtualisation software. It will also mark the first time Red Hat has included new community-contributed features, called Extras.

The software has been delayed by a week thanks to legal hiccup over permission for the OS' codename, yet to be determined, said Jeremy Katz, a Red Hat engineer.

Fedora Core 4 will include a number of performance enhancements, integration with Red Hat's Red Hat Global File System, and updated versions of the compiler and desktop software used in Red Hat's Linux.

But the most high-profile new feature remains Xen virtualisation software, which allows users to run more than one copy of an operating system on the same computer. When used in combination with Intel's Vanderpool Technology, expected to begin appearing in chipsets soon, Xen allows users to run copies of both Windows and Linux simultaneously on the same computer.

Xen is still in the early stages of development, but over the next year Red Hat plans to develop tools that will make it easier for administrators to configure and manage "virtual" copies of the operating system using Xen, said Rik van Riel, a Red Hat engineer.

Red Hat originally released Fedora as an unsupported alternative to its Red Hat Enterprise Linux (RHEL) product. Fedora includes many cutting-edge features, such as Xen, that are intended for inclusion in upcoming versions of RHEL. Unlike Red Hat's commercial products, however, users are free to make as many copies of Fedora as they wish, without paying for support licenses.

Red Hat was initially criticised for dictating what features would and would not be in the Fedora release. This year, however, it launched the Extras project as a way to let contributors outside of Red Hat decide what features to add to the release, said Michael Tiemann Red Hat's chief technology officer. "We are basically saying, 'OK, we heard you and here's our response'," he said.