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Subject: Re: [OMPI users] Some Newbie questions / ssh_known_hosts
From: Reuti (reuti_at_[hidden])
Date: 2009-06-29 07:17:21


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<aumanga_at_[hidden]> 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
>> <aumanga_at_[hidden]> 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
>>>
>>>
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>>
>> --
>> Vipin K.
>> Research Engineer,
>> C-Dot, Bangalore, India
>>
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