Hi, I was able to compile & install MPICH on a master virtual machine for a user cosy11. There are identical 2 VM running with IPs 198.125.163.212, 198.125.163.207 I picked IP=212 as my master node. On this node I can run pi computation on two processes: cosy11@mpi-be6bebee-55e3-4901-a5bb-637395ba46f6 mpich-3.1]$ mpiexec -n 2 ./examples/cpi Process 1 of 2 is on mpi-be6bebee-55e3-4901-a5bb-637395ba46f6 Process 0 of 2 is on mpi-be6bebee-55e3-4901-a5bb-637395ba46f6 pi is approximately 3.1415926544231318, Error is 0.0000000008333387 wall clock time = 0.000310 The next step of instruction (h) http://www.mpich.org/static/downloads/3.1/mpich-3.1-README.txt tells me to define machinefile , below is my definition: $ cat machinefile 198.125.163.207:2 198.125.163.212:2 Note, I verified I can ssh to both machines from IP=212, but I must type in the password $ ssh [email protected] $ ssh [email protected] Now, I try to compute pi on both VMs and mpiexec get stuck asking for the password (see the screen shot) mpiexec -f machinefile -n 4 ./examples/cpi I must somehow pass credentials for user=cosy11 to both VMs - how? Have I missed this step of the instruction? Do I need to use ssh-key added to my ssh-add list on IP=212 to make mpiexec to work with remote hosts? Is there other solution you prefer? Can you help me how to overcome that? Thanks Jan