[mpich-discuss] Running an mpi program that needs to access /dev/mem

Pavan Balaji balaji at mcs.anl.gov
Thu Jun 13 10:17:15 CDT 2013


No.  Think of hydra as an ssh program.  If you run mpiexec as root, 
it'll try to ssh as root.  You'll need to make sure ssh as root is 
passwordless.

  -- Pavan

On 06/13/2013 10:08 AM, Lee, Eibhlin wrote:
> My apologies,
> So hydra is in effect a super user?
> Eibhlin
> ________________________________________
> From: Pavan Balaji [balaji at mcs.anl.gov]
> Sent: 13 June 2013 16:02
> To: Lee, Eibhlin
> Cc: discuss at mpich.org
> Subject: Re: [mpich-discuss] Running an mpi program that needs to access /dev/mem
>
> Please don't drop the mailing list from the cc.
>
> You can do an strace to see where /dev/mem is being used.
>
> If you are using multiple nodes, hydra only relies on passwordless ssh.
>    It doesn't really care what the user id is (root or non-root).
>
>    -- Pavan
>
> On 06/13/2013 09:27 AM, Lee, Eibhlin wrote:
>> Unfortunately I didn't come across this mailing list until recently. Sods law.
>> ./main does not work but sudo ./main does work.
>> Could hydra compile and run a program where this is the case?
>> I ask because the only way I'll be able to get around using sudo is to change ownership of /dev/mem. It goes without saying that that's dangerous!
>> Eibhlin
>> ________________________________________
>> From: Pavan Balaji [balaji at mcs.anl.gov]
>> Sent: 13 June 2013 15:21
>> To: discuss at mpich.org
>> Cc: Lee, Eibhlin
>> Subject: Re: [mpich-discuss] Running an mpi program that needs to access        /dev/mem
>>
>> smpd was mainly meant for windows support.  It is now deprecated, so we
>> don't officially support that.  Someone on the mailing list might help,
>> but no promises.
>>
>> With respect to hydra, problems with that is what you should have
>> reported on this mailing list and we would have tried to help.  :-)
>>
>> If ./main itself is not working, there's no hope of getting it to work
>> with mpiexec.  You'll need to debug that first.
>>
>>     -- Pavan
>>
>> On 06/13/2013 09:09 AM, Lee, Eibhlin wrote:
>>> Pavan,
>>> I had a lot of trouble getting hydra to work without having to enter a password/passphrase. I saw the option to pass a phrase in the mpich installers guide. I eventually found that for that command you needed to use the smpd process manager. That's the only reason I chose smpd over hydra.
>>> As to your other suggestion. I ran ./main and the same error (Can't open /dev/mem...) appeared. sudo ./main works but of course without multiple processes.
>>> Eibhlin
>>> ________________________________________
>>> From: discuss-bounces at mpich.org [discuss-bounces at mpich.org] on behalf of Pavan Balaji [balaji at mcs.anl.gov]
>>> Sent: 13 June 2013 14:34
>>> To: discuss at mpich.org
>>> Subject: Re: [mpich-discuss] Running an mpi program that needs to access        /dev/mem
>>>
>>> I just saw your older email.  Why are you using smpd instead of the
>>> default process manager (hydra)?
>>>
>>>      -- Pavan
>>>
>>> On 06/13/2013 08:05 AM, Pavan Balaji wrote:
>>>>
>>>> What's "-phrase"?  That's not a recognized option.  I'm not sure where
>>>> the /dev/mem check is coming from.  Try running ~/main without mpiexec
>>>> first.
>>>>
>>>>      -- Pavan
>>>>
>>>> On 06/13/2013 06:56 AM, Lee, Eibhlin wrote:
>>>>> Hello all,
>>>>>
>>>>> I am trying to use two raspberry-pi to sample and then process some
>>>>> data. The first process samples while the second processes and vice
>>>>> versa. To do this I use gpio and also mpich-3.0.4 with the process
>>>>> manager smpd. I have successfully run cpi on both machines (from the
>>>>> master machine). I have also managed to run a similar program but
>>>>> without the MPI, this involved compiling with gcc and when running
>>>>> putting sudo in front of the binary file.
>>>>>
>>>>> When I combine these two processes I get various error messages.
>>>>> For input:
>>>>> mpiexec -phrase cat -machinefile machinefile -n 2 ~/main
>>>>> the error is:
>>>>> Can't open /dev/mem
>>>>> Did you forget to use 'sudo .. ?'
>>>>>
>>>>> For input:
>>>>> sudo mpiexec -phrase cat -machinefile machinefile -n 2 ~/main
>>>>> the error is:
>>>>> sudo: mpiexec: Command not found
>>>>>
>>>>> I therefore put mpiexec into /usr/bin
>>>>>
>>>>> now for input:
>>>>> sudo mpiexec -phrase cat -machinefile machinefile -n 2 ~/main
>>>>> the error is:
>>>>> Can't open /dev/mem
>>>>> Did you forget to use 'sudo .. ?'
>>>>>
>>>>> Does anyone know how I can work around this?
>>>>> Thanks,
>>>>> Eibhlin
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> discuss mailing list     discuss at mpich.org
>>>>> To manage subscription options or unsubscribe:
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>>>>>
>>>>
>>>
>>> --
>>> Pavan Balaji
>>> http://www.mcs.anl.gov/~balaji
>>> _______________________________________________
>>> discuss mailing list     discuss at mpich.org
>>> To manage subscription options or unsubscribe:
>>> https://lists.mpich.org/mailman/listinfo/discuss
>>> _______________________________________________
>>> discuss mailing list     discuss at mpich.org
>>> To manage subscription options or unsubscribe:
>>> https://lists.mpich.org/mailman/listinfo/discuss
>>>
>>
>> --
>> Pavan Balaji
>> http://www.mcs.anl.gov/~balaji
>>
>
> --
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji
>

-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji



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