[mvapich-discuss] [rsh] <defunct> ????

[Pavel Shamis]

Hi all,
I what extend the answer on question "Why ssh is default".  
I see follow reasons:

1. SSH is remote shell that is installed by default on all distribution.
2. RSH use privileged ports for client process. The maximum number of
these ports for UNIX system is 1024 and most of them are used by other
applications (cat /etc/services). So on big clusters the rsh fails to
allocate ports for all jobs. SSH does not have this limitation. 
3. If application that launched via rsh exits with error the rsh does
not report it. For example;
 	rsh node1 lsss && echo "Test PASS"
this command will report PASS but the rsh will report error that lsss
does not exits.
mpirun_rsh use the same mechanism (rsh) and will report (print) error
but the exits status will be incorrect.
SSH does not have this problem, and it reports correct exit code.

Regards,
Pasha
   


> > Can you explain why you choose ssh as default ?
> 
> We chose ssh as default since many Linux distributions 
> disable rsh because of security reasons. We believe the 
> choice of rsh/ssh shouldn't impact end application 
> performance, because once the jobs are launched all 
> communications happen over InfiniBand (and unencrypted).
> 
> However, the final choice of rsh/ssh is left to the user.
> 
> > I have not upgraded to 1.8.1 or 1.8.2 yet, because I am 
> afraid of that 
> > it may cause other unknown issues.
> 
> OK. If you face any problems with the current installation, 
> we'll be glad if you could consider upgrading. The latest 
> IBGD stacks feature updated firmware too.
> 
> Thanks,
> Sayantan.
> 
> --
> http://www.cse.ohio-state.edu/~surs
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