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Subject: Re: [OMPI users] Accessing OpenMPI processes over Internet using ssh
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-11-24 21:47:45


On Nov 24, 2011, at 2:00 AM, Reuti wrote:

> Hi,
>
> Am 24.11.2011 um 05:26 schrieb Jaison Paul:
>
>> I am trying to access OpenMPI processes over Internet using ssh and not quite successful, yet. I believe that I should be able to do it.
>>
>> I have to run one process on my PC and the rest on a remote cluster over internet. I have set the public keys (at .ssh/authorized_keys) to access remote nodes without a password.
>>
>> I use hostfile to run mpi. It will read something like:
>> -----------------------------
>> localhost
>> user_at_[hidden]
>
> this is not a valid syntax for Open MPI.

This isn't correct - we have long supported that syntax in a hostfile, and there is no issue with having a different user name at each node.

Jaison: are you sure your nodes are setup for password-less ssh? In other words, have you setup your .ssh files on the remote nodes so they will allow us to ssh a process on them without providing a password? This is the typical problem we see.

>
>
>> -----------------------------
>> But it fails.
>>
>> The issue seems to be the user! That is, the user on my PC is different to that of user at remotehosts. That's my assumption.
>>
>> Is this the problem? Is there any work-around to solve this issue? Do I need to have same username at all nodes to solve this issue?
>
> You can define nicknames for an ssh connection in a file ~/.ssh/config like:
>
> Host foobar
> User baz
> Hostname the.remote.server.demo
> Port 1234
>
> While this will work with any nickname for an ssh connection, in your case the nickname must match the one specified in the hostfile, as Open MPI won't use this lookup file:
>
> Host remotehost.com
> User user
>
> ssh should then use the entries therein to initiate the connection. For details you can have a look at `man ssh_config`.
>
> -- Reuti
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