[gmx-users] secure gromacs lam setup?

[Jack Howarth]

    I have built and installed both the gromacs and gromacs-mpi rpms
on a dual Xenon Fedora Core 2 Linux workstation. The standard gromacs
works fine however it seems to only use one of the two cpus despite
using threaded code. Thus I am interested in setting up lam-mpi to
run on this box allowing gromacs to fully utilize both cpu's. However
I am very concerned about the security implications and have the
following questions....

1) What is the most secure approach to setting up lam-mpi on a single
dual cpu workstation if that workstation is going to be the only 
member of the cluster? Is it possible to make only localhost the
lam member so that only rsh from localhost to localhost is possible?
2) Related to the question above, if lam is running on a single node
with 2 cpus under what conditions will the messages sent via the mpi
protocol go over the external internet? That is if a have a machine
foobar.bar with 2 cpus and that is the only node in use, will the
mpi messages sent for the 2 cpus on the machine be slowed by going
out onto the nic interface or will they be short-circuited through
the localhost network interface.
 
What I would like to end up with is a lam configuration where rsh
only accepts access from the single dual processor machine itself to
limit the security risk. Also since the machine in question only has
fast ethernet network access I would like to prevent the mpi traffic
from being slowed by going out onto the network by having it 
redirected through the localhost interface. 
      Any hints on how to configure lam to meet these goals would 
be highly appreciated.
                    Jack Howarth