[Beowulf] cloning issue, hidden module dependency

Joe Landman landman at scalableinformatics.com
Mon Dec 8 13:05:20 PST 2008

David Mathog wrote:
> Mark Hahn wrote:
>>> Any ideas where else the amd74xx module load command might be hidden
> away?
>> in the initrd, I bet...
> That was it, unfortunately.  Mandriva went from a very small, and very
> general sort of "init" script to a larger, very machine specific "init".
>  See the thread cited in the original post for more details.  Sort of a
> PITA for cloning purposes - much easier to shuffle around a couple of
> small files like modprobe.conf than to have to build a new initrd for
> each node with different hardware.  FC, RedHat, CentOS etc. might
> have similar changes, since they are all closely related.

Well RHEL is annoying in that if you decide to use a custom kernel and a 
software raid, you are, for lack of a better term, toast (if you stick 
with their tools/config).  This is not to say that it is impossible, in 
fact it works very well in other distributions.

We worked around this for some customers, but the surgery is neither 
easy nor pleasant.   It involves upgrading nash, initrd-tools, and quite 
a few other things.  This is because RHEL 5.x still uses dmraid for 
building software RAID while FCx (x>=8) have switched to mdadm (go 
figure).  The latter works.

Unfortunately, all of this is buried in initrd.  Doing initrd surgery is 
not for the faint of heart.


Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://www.scalableinformatics.com
phone: +1 734 786 8423 x121
fax  : +1 866 888 3112
cell : +1 734 612 4615

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