[Beowulf] Puzzling Intel mpi behavior with slurm

[Faraz Hussain]

Here's something quite baffling. I have a cluster running slurm but  
have not setup passwordless ssh for a user yet. So when the user runs  
"mpirun -n 2 -hostfile hosts hostname", it will hang because of ssh  
issue. That is expected.

Now the baffling thing is the mpirun command works inside a slurm  
script! How can it work if passwordless ssh has not been configured?  
Does slurm use some different authentication (munge?) to login to the  
hosts and execute the hostname command?

Or does slurm have some fancy behind the scenes integration with Intel mpi ?