ATLAS grid compute cluster with virtualized service nodes

The ATLAS Computing Grid consists of several hundred compute clusters distributed around the world as part of the Worldwide LHC Computing Grid (WLCG). The Grid middleware and the ATLAS software which has to be installed on each site, often require a certain Linux distribution and sometimes even specific version thereof. On the other hand, mostly due to maintenance reasons, computer centres install the same operating system and version on all computers. This might lead to problems with the Grid middleware if the local version is different from the one for which it has been developed. At RZG we partly solved this conflict by using virtualization technology for the service nodes. We will present the setup used at RZG and show how it helped to solve the problems described above. In addition we will illustrate the additional advantages gained by the above setup.