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Subject: Re: [OMPI users] Accessing OpenMPI processes over Internet using ssh
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-11-30 09:30:13


This has come up before - I would suggest doing a quick search of "ec2" on our user list. Here is one solution:

On Jun 14, 2011, at 10:50 AM, Barnet Wagman wrote:

> I've put together a simple system for running OMPI on EC2 (Amazon's cloud computing service). If you're interested, see
>
> http://norbl.com/ppe-ompi.html
>
>
> Barnet Wagman

On Nov 30, 2011, at 4:03 AM, Jaison Paul wrote:

>
> Ralph Castain <rhc <at> open-mpi.org> writes:
>
>>
>>
>> On Nov 24, 2011, at 2:00 AM, Reuti wrote:
>>
>
>
> Thanks a lot to Ralph and Reuti.
>
> Actually we are trying to use EC2 nodes as compute nodes and my local PC as host
> node.
>
> Happy to know that it is OK to use user<at>somehost.com
>
> We used that but failed. Would try again.
>
> Yes, we have set up .ssh file on remote EC2 hosts. Is there anything else that
> we should be taking care of when dealing with EC2?
>
> Jaison
>
>
>>> 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> remotehost.com
>>>
>>> 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
>>> _______________________________________________
>>> users mailing list
>>> users <at> open-mpi.org
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>
>
>
>
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