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Subject: [OMPI users] Setting up Open MPI to run on multiple servers
From: Rayne (lancer6238_at_[hidden])
Date: 2008-08-11 20:25:51


Hi all,
I am trying to set up Open MPI to run on multiple servers, but as I
have very little experience in networking, I'm getting confused by the
info on open-mpi.org, with the .rhosts, rsh, ssh etc.

Basically what I have now is a PC with Open MPI installed. I want to
connect it to, say, 10 servers, so I can run MPI programs on all 11
nodes. From what I've read, I think I need to install Open MPI on the
10 servers too, and there must be a shared directory where I keep all
the MPI programs I've written, so all nodes can access them.

Then I need to create a machine file on my local PC (I found a default
hostfile "openmpi-default-hostfile" in {prefix}/etc/. Can I use that
instead so I need not have "-machinefile machine" with every mpiexec?)
with the list of the 10 servers. I'm assuming I need to put down the
IP addresses of the 10 servers in this file. I've also read that the
10 servers also need to each have a .rhosts file that tells them the
machine (i.e. my local PC) and user from which the programs may be
launched from. Is this right?

There is also the rsh/ssh configuration, which I find the most
confusing. How do I know whether I'm using rsh or ssh? Is following
the instructions on http://www.open-mpi.org/faq/?category=rsh under
"3: How can I make ssh not ask me for a password?" sufficient? Does
this mean that when I'm using the 10 servers to run the MPI program,
I'm login to them via ssh? Is this necessary in every case?

Is doing all of the above all it takes to run MPI programs on all 11
nodes, or is there something else I missed?

Thank you.

Regards,
Rayne

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