Cluster Poll Results (tangent into OS choices)

Robert G. Brown rgb at phy.duke.edu
Tue Nov 4 14:59:30 EST 2003


On Tue, 4 Nov 2003, John Hearns wrote:

> If I may, I'll join Bob in a blue sky thought. How about applications
> being installed as RPMs? Then the RPM would have dependencies - 
> application Z needs library-b between x and y. 
> Could you then get a message back saying 'sorry - this cluster won't
> support this application: it needs x-y'
> 
> Sorry - a huge bly sky here. But we do keep hearing about grid and
> infrastructure on demand.

Curiously and not terribly coincidentally, we REQUIRE all our linux
applications to be installed as RPMs at Duke.  Even commercial ones we
get in some other form, we typically repackage into an RPM.  Otherwise
it IS very difficult to know whether dependencies are being met or
warped, and a good rpm also facilitates de-installation (an rpm --erase
or yum remove away).

This isn't to say that individuals may not install applications that
aren't rpm's on their own systems from time to time or force rpm
installs from mismatched distributions without a rebuild, but this is
the Dark Path and leads to RPM Hell.

This also means that you don't even get the message above.  If you use
yum as in:

 yum install clusterapp

and clusterapp is on one of the repositories in its /etc/yum.conf, then
yum will fire back a message such as

"clusterapp needs packages: clusterlib clustergui clusterdevel
to be installed.  Install (y/n)?:

Press y and all four packages are grabbed and installed so clusterapp is
ready to run, possibly from the clustergui you may not have known
existed.  Or use yum -y -d 0 install clusterapp and install clusterapp
AND its dependencies right now and you mean it and only say something if
you encounter a condition that makes the install fail.  You also get
warnings if clusterapp contains and wishes to replace files "belonging"
to installed packages, if there are obsoletes in its dependencies, if
there are dependency loops -- basically if there is anything whatsoever
that cannot be automagically resolved and requires human intervention to
make happen safely.  

(Getting such a message usually means that your system is in RPM Hell
from a previous RPM force; NOT getting such a message when you should
have usually means that you built something and installed it from source
so that it isn't in the rpm db but is on the system anyway.)

If you install strictly RPM's strictly with anaconda or yum, and never
override or force anything, your system has an excellent chance of
staying out of RPM Hell and being consistently automagically
installable, upgradeable, updateable, and so forth.  If nothing else
when you put a "bad rpm" on your repository (and there are plenty out
there) it won't install and you'll be forced to fix/rebuild it so that
it does instead of breaking your system with a force.

   rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu



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