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Subject: Re: [OMPI users] Problem with mpirun -preload-binary option
From: Qing Pang (qing.pang_at_[hidden])
Date: 2009-11-12 15:50:03

Now that I have passwordless-ssh set up both directions, and verified
working - I still have the same problem.
I'm able to run ssh/scp on both master and client nodes - (at this
point, they are pretty much the same), without being asked for password.
And mpirun works fine if I have the executable put in the same directory
on both nodes.

But when I tried the preload-binary option, I still have the same
problem - it asked me for the password of the node running mpirun, and
then tells that scp failed.


Josh Wrote:

Though the --preload-binary option was created while building the
checkpoint/restart functionality it does not depend on
checkpoint/restart function in any way (just a side effect of the
initial development).

The problem you are seeing is a result of the computing environment
setup of password-less ssh. The --preload-binary command uses 'scp' (at
the moment) to copy the files from the node running mpirun to the
compute nodes. The compute nodes are the ones that call 'scp', so you
will need to setup password-less ssh in both directions.

-- Josh

On Nov 11, 2009, at 8:38 AM, Ralph Castain wrote:

> I'm no expert on the preload-binary option - but I would suspect that
is the case given your observations.
> That option was created to support checkpoint/restart, not for what
you are attempting to do. Like I said, you -should- be able to use it
for that purpose, but I expect you may hit a few quirks like this along
the way.
> On Nov 11, 2009, at 9:16 AM, Qing Pang wrote:
> > Thank you very much for your help! I believe I do have password-less
ssh set up, at least from master node to client node (desktop -> laptop
in my case). If I type >ssh node1 on my desktop terminal, I am able to
get to the laptop node without being asked for password. And as I
mentioned, if I copy the example executable from desktop to the laptop
node using scp, then I am able to run it from desktop using both nodes.
> > Back to the preload-binary problem - I am asked for the password of
my master node - the node I am working on - not the remote client node.
Do you mean that I should set up password-less ssh in both direction?
Does the client node need to access master node through password-less
ssh to make the preload-binary option work?
> >
> >
> > Ralph Castain Wrote:
> >
> > It -should- work, but you need password-less ssh setup. See our FAQ
> > for how to do that, if you are unfamiliar with it.
> >
> > On Nov 10, 2009, at 2:02 PM, Qing Pang wrote:
> >
> > I'm having problem getting the mpirun "preload-binary" option to work.
> >>
> >> I'm using ubutu8.10 with openmpi 1.3.3, nodes connected with
Ethernet cable.
> >> If I copy the executable to client nodes using scp, then do mpirun,
everything works.
> >>
> >> But I really want to avoid the copying, so I tried the
-preload-binary option.
> >>
> >> When I typed the command on my master node as below (gordon-desktop
is my master node, and gordon-laptop is the client node):
> >>
> >>
> >> gordon_at_gordon-desktop:~/Desktop/openmpi-1.3.3/examples$ mpirun
> >> -machinefile machine.linux -np 2 --preload-binary $(pwd)/hello_c.out
> >>
> >>
> >> I got the following:
> >>
> >> gordon_at_gordon-desktop's password: (I entered my password here,
why am I asked for the password? I am working under this account anyway)
> >>
> >>
> >> WARNING: Remote peer ([[18118,0],1]) failed to preload a file.
> >>
> >> Exit Status: 256
> >> Local File:
> >> Remote File: /home/gordon/Desktop/openmpi-1.3.3/examples/hello_c.out
> >> Command:
> >> scp
> >> /tmp/openmpi-sessions-gordon_at_gordon-laptop_0/18118/0/hello_c.out
> >>
> >> Will continue attempting to launch the process(es).
> >>
> >>
> >> mpirun was unable to launch the specified application as it could
not access
> >> or execute an executable:
> >>
> >> Executable: /home/gordon/Desktop/openmpi-1.3.3/examples/hello_c.out
> >> Node: node1
> >>
> >> while attempting to start process rank 1.
> >>
> >>
> >> Had anyone succeeded with the 'preload-binary' option with the
similar settings? I assume this mpirun option should work when compiling
openmpi with default options? Anything I need to set?
> >>
> >> --qing
> >>
> >>