When Hyper-V was released in June 2008 Microsoft initially only supported the SUSE Enterprise Linux distribution by releasing so called Linux Integration Components providing drivers for synthetic devices. In July 2009 when Hyper-V 2.0 was released, Microsoft extended support to Red Hat Enterprise Linux. Today at its annual Teched conference in Atlanta, Microsoft announced that it will now support the CentOS Linux distribution.
After Microsoft released the Linux Integration Components for hyper-V under the GPL v2 license, many efforts have been taken by the community to extend the Integration Services to other distributions, like for example by Yusuf Ozturk which released a Debian package to install the Integration Services, this remains unsupported by Microsoft though.