I was configuring Xen virtual machines to run MPI programs. Running MPI,Hadoop, or even CGL-MapReduce require password less login between the nodes of a cluster.
It is the same old steps that we need to perform, but found this simple tutorial which list the process very succinctly.
To get MPI to work you also need to add the following line to your bash (or your shell) profile.
export LAMRSH="ssh -x"