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Subject: Re: [OMPI users] control openmpi or force to use pbs?
From: Duke Nguyen (duke.lists_at_[hidden])
Date: 2013-02-06 06:23:54


On 2/6/13 1:03 AM, Gus Correa wrote:
>
> On 02/05/2013 08:52 AM, Jeff Squyres (jsquyres) wrote:
>> To add to what Reuti said, if you enable PBS support in Open MPI,
when users "mpirun ..." in a PBS job, Open MPI will automatically use
the PBS native launching mechanism, which won't let you run outside of
the servers allocated to that job.
>>
>> Concrete example: if you qsub a job and are allocated node A, B, and
C, but then try to run with "mpirun --host D,E,F ...", you'll get an error.
>>
>> That being said -- keep in mind what Reuti said: if users are allowed
to ssh between nodes that are not allocated to them, then they can
always bypass this behavior and use just Open MPI's ssh support to
launch on nodes D, E, F (etc.).

>> On Feb 5, 2013, at 2:46 AM, Reuti<reuti_at_[hidden]> wrote:
> Can the users use a plain ssh between the nodes? If they are forced to
> use the TM of Torque instead, it should be impossible to start a job
> on a non-granted machine.
>
Thanks Reuti and Jeff, you are right, users should not be allowed to ssh
to all nodes, which is how our cluster was set up: users can even
password-less ssh to any node. I know this is not appropriate question
in OpenMPI forum, but how can we setup so that user can only ssh (with
password) to nodes that are allocated to them at the time of qsub'ing? I
am still new to all of this cluster thing :)

>
> Besides Reuti's and Jeff's suggestions.
>
> If you build your own Torque/PBS with PAM support
> (./configure --with-pam [other configure flags]),
> you can prevent users that are not running a Torque/PBS job
> on a node to launch processes in that node.
>
> See this:
>
http://docs.adaptivecomputing.com/torque/4-1-3/help.htm#topics/1-installConfig/customizingTheInstall.htm
>
> Of course you will need to rebuild your OpenMPI with Torque
> support again, after you install a version of Torque with PAM
> support.
>
> This is mostly a Torque/Maui issue, with a bit of an MPI issue.
> You may get more help about this on the Torque and Maui
> mailing lists, and in their archives you may find more specific
> guidance on what you need to add to the pam/security
> files to make it work.

Thanks for this! I will try this --with-pam when our test job finishes.

>
> Torque with PAM support is not 100% foolproof,
> because users that *are* running a Torque/PBS job on
> a node can still cheat and launch more processes there,
> but it helps restrict the problem to this case.
>
> Some sys admins also add a cleanup/sweep routine to the
> Torque epilogue script to kill any processes belonging to
> the user whose job just finished.
> However, this not very good because that user may have another
> legitimate job still running there.
> Other cleanup strategies are possible, and you may find some
> suggestions and even scripts if you google around.
>
> Moreover, if you configure your scheduler (Maui?) to
> assign full nodes to jobs (no node sharing),
> the cheaters will be cheating on
> themselves, not stepping on other users' toes.
> Look for "JOBNODEMATCHPOLICY" here:
> http://docs.adaptivecomputing.com/maui/a.fparameters.php
>
> Assigning full nodes to jobs ("EXACTNODE") may or may not be a
> good choice for you.
> E.g. you may consider it wasteful, if there are many serial
> jobs or parallel jobs running only on a few processors, in
> which case you may want to pack those jobs in the fewest
> nodes possible ("EXACTPROC"), so as to have a maximum throughput.
> However, "no node sharing" helps preventing cheaters
> to bother other users that are running jobs on the same node,
> and it is not bad at all if most of the jobs are parallel
> and use many cores (say, >= number of cores per node).

Yes, we use Maui, but I let it at its' default settings since I have no
idea and experience about maui's options. I like EXACTPROC option. Our
cluster is small so that might be better for us.