  The NEMO High Performance Computing Cluster at the University of Freiburg has
been made available to researchers of the ATLAS and CMS experiments. Users
access the cluster from external machines connected to the World-wide LHC
Computing Grid (WLCG). This paper describes how the full software environment
of the WLCG is provided in a virtual machine image. The interplay between the
schedulers for NEMO and for the external clusters is coordinated through the
ROCED service. A cloud computing infrastructure is deployed at NEMO to
orchestrate the simultaneous usage by bare metal and virtualized jobs. Through
the setup, resources are provided to users in a transparent, automatized, and
on-demand way. The performance of the virtualized environment has been
evaluated for particle physics applications.
