[Beowulf] problem of mpich-1.2.7p1

Gus Correa gus at ldeo.columbia.edu
Thu Feb 4 12:09:43 PST 2010

Yes, Mark, you are right.

Passwordless ssh is not a strict requirement,
although it is a simple way to make things work.
Yes, host based trust is better than unencrypted private keys.
I don't even know if the cluster in question is
connected to the Internet, though.

My suggestions were directed to someone who is still using
MPICH-1, claimed to have trouble with it,
not to be familiar to clusters and MPI,
and to have a pressing deadline.
Therefore, I thought it would be more helpful to give him
simple and focused suggestions,
rather than a full gamut of possibilities.

I guess it would be a great help to him if you post
simple instructions (or a link) on how to setup passwordless ssh
through host based trust.

Gus Correa

Mark Hahn wrote:
>> In MPICH2 you need to establish passwordless ssh (not rsh!)
>> connection across your machines.
> it should be said that mpich2 doesn't strictly require this.
> all mpi flavors can operate with other spawning methods - some have 
> hooks to be spawned by the resource manager, for instance, which 
> bypasses ssh/rsh type access.
>> In OpenMPI you also need to establish passwordless ssh connection
> same for OpenMPI: doesn't actually require passwordless ssh.
> but if you do want passwordless ssh, IMO the only sane solution is to 
> configure hostbased trust.  having an unencrypted private key in your 
> home directory is hideous (moral equivalent of putting your password in 
> a file, in the clear...)
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