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Subject: [OMPI users] How to use a wrapper for ssh?
From: Paul Kapinos (kapinos_at_[hidden])
Date: 2011-07-12 16:34:24


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?

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?

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