I have been running MPI programs on my testbed with ssh without problems. But when I wanted to switch to rsh to avoid encryption and run a program with mpirun, there is no output. I inspected the traffic with Wireshark and there is a TCP packet with PUSH flag, where the data says:
bash: orted: command not found
Open MPI is installed in the same directory in both machines, and they both have Ubuntu 16.04. I set it so there is no password for rsh needed within the testbed from the other machines. I can run programs on the remote machine with rsh, but not mpirun. Any idea what the problem could be?