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

Barnet Wagman

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

Ralph Castain <rhc <at>> 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

Happy to know that it is OK to use user<at>

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?



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:
user <at>

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:

  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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