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Subject: Re: [OMPI users] How to use a wrapper for ssh?
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-07-12 23:40:35


On Jul 12, 2011, at 2:34 PM, Paul Kapinos wrote:

> Hi OpenMPI folks,
>
> Using the version 1.4.3 of OpenMPI, I wanna to wrap the 'ssh' calls, which are made from the OpenMPIs 'mpiexec'. For this purpose, at least two ways seem to be possible for me:
>
> 1. let the wrapper have the name 'ssh' and paste the path where it is into the PATH envvar *before* the path to real ssh
>
> Q1: Would this work?

Probably - but I wouldn't recommend it

>
> 2. use MCA parameters described in
> http://www.open-mpi.org/faq/?category=rsh#rsh-not-ssh
> to bend the call to my wrapper, e.g.
> export OMPI_MCA_plm_rsh_agent=WrapPer
> export OMPI_MCA_orte_rsh_agent=WrapPer
>
> the oddly thing is, that the OMPI_MCA_orte_rsh_agent envvar seem not to have any effect, whereas OMPI_MCA_plm_rsh_agent works.
> Why I believe so?

orte_rsh_agent doesn't exist in the 1.4 series :-)

Only plm_rsh_agent is available in 1.4. "ompi_info --param orte all" and "ompi_info --param plm rsh" will confirm that fact.

>
> Because "strace -f mpiexec ..." says still trying for opening 'ssh' if OMPI_MCA_orte_rsh_agent is set, and correctly trying to open the 'WrapPer' iff OMPI_MCA_plm_rsh_agent is set.
>
> Q2: Is the supposed non-functionality of OMPI_MCA_orte_rsh_agent a bug, or do I have just misunderstood something?
>
> Best wishes,
> Paul
>
> P.S. reproducing: just set the envvars and do 'strace -f mpiexec ...'
>
> example:
>
> export OMPI_MCA_plm_rsh_agent=WrapPer
> ---> look'n for 'WrapPer';
> stat64("/opt/lsf/8.0/linux2.6-glibc2.3-x86_64/bin/WrapPer", 0xffff8324) = -1 ENOENT (No such file or directory)
>
> export OMPI_MCA_orte_rsh_agent=WrapPer
> (do not forget to unset OMPI_MCA_plm_rsh_agent :o)
> ---> still looking for 'ssh'
> stat64("/opt/lsf/8.0/linux2.6-glibc2.3-x86_64/bin/ssh", 0xffff8324) = -1 ENOENT (No such file or directory)
>
> ===> OMPI_MCA_orte_rsh_agent does not work?!
>
> --
> Dipl.-Inform. Paul Kapinos - High Performance Computing,
> RWTH Aachen University, Center for Computing and Communication
> Seffenter Weg 23, D 52074 Aachen (Germany)
> Tel: +49 241/80-24915
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