Re: [OMPI users] Some Newbie questions / ssh_known_hosts

Mon, 29 Jun 2009 07:17:32 -0400 

Hi,

Am 29.06.2009 um 08:08 schrieb jody:


Hi Umanga

Yes, ssh (or rsh) should be configured on every machine, and it must
be configured
in such a way that no passwords are needed to make a connection. For example, for passwordless connection using ssh i place every node's public key into 
the file ~/.ssh/authorized_keys of every node.
this is the common approach. But instead of preparing these keys for everyone, you can also adjust /etc/ssh/ssh_known_hosts on all of the machines one time and supply there the keys from the other machines and have there three names per entry for a) the hostname, b) TCP/IP address and c) FQDN. This file will then be used twice: on the target machine to allow the source machine to connect, and on the source machine to avoid the cluttering of the user's ~/.ssh/known_hosts file.
There is a program called ssh-keyscan to collect the hostkeys from all the machines. 

-- Reuti



And, yes, 1.2.7 is a rather old version - the current one is 1.3.2. It
would be good
if you could update your version to a newer one.

Jody

On Mon, Jun 29, 2009 at 7:00 AM, Ashika Umanga
Umagiliya<auma...@biggjapan.com> wrote:

Hi Vipin ,
Thanks alot for the reply.
I went through the FAQ and it also answered some of my questions.
But my problem is, since I am using TCP/Ethernet I guess that MPI uses 
SSH/RSH to communicate between peers.
And for that, each peer should have the copy of the application right? 

I use 1.2.7rc2 (from Debian/Lenny repo) , and I didn't see the option
"--preload-binary" , is it because the lower version?

Bets regards,
umanga.



vipin kumar wrote:

Hi,
I am not expert, I am user like you but I think I can help you,

Q. After installing OpenMPI on each machine ,do i need to run a
service/daemon on each machine?
Ans. No, not at all, Open MPI takes care of that for you.

Q. How does peers in MPI environment communicate ?
Ans. Using Communicator(name of the group of processes to whom it belongs, 
technically handle) and rank of the process in that Communicator.

Q. After implementing parallel program , do I have to install the
application on every machine ?
Ans. Not necessary. Use "--preload-binary" option while launching the
application through mpirun or mpiexec.

Useful links:
1. http://www.open-mpi.org/faq/?category=running#simple-spmd-run
2. http://www.open-mpi.org/faq/
3. man page for mpirun

Regards,
Vipin K.

On Mon, Jun 29, 2009 at 8:21 AM, Ashika Umanga Umagiliya
<auma...@biggjapan.com> wrote:


Greeting all,
I am new to Open MPI and I have some newbie questions. I have given 4 
machines at our laboratory to set up Open MPI.Our net work is simply
TCP/Ethernet running Debian Linux.

1) After installing OpenMPI on each machine ,do i need to run a
service/daemon on each machine? (How does peers in MPI environment
communicate ?)

2) After implementing parallel program , do I have to install the
application on every machine ? (I thought the program automatically
propagated to other peers , like in RMI applications? )



Thanks in advance,
Umanga


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--
Vipin K.
Research Engineer,
C-Dot, Bangalore, India

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