[Beowulf] /dev/random entropy on stateless/headless nodes

[Stuart Barkley]

We have a couple of clusters with headless, diskless and stateless
nodes using CentOS 5.  One of our users just ran onto a problem with
/dev/random blocking due to the lack of entropy.

I had the user change the program to use /dev/urandom and this has
handled the immediate problem.

/proc/sys/kernel/random/entropy_avail shows 0 across the compute
nodes even just after boot.

It appears that our Ethernet and Infiniband drivers don't add any
entropy to the random pool.

hw_random/intel-rng doesn't seem to work on our systems.

Some questions:

Do others have this problem?  What do you do?

Do you just refer users to /dev/urandom?

Do you modify network drivers to introduce entropy?

Are there other suggested methods of adding entropy to /dev/random?

Are there ways to introduce entropy from the random number generator
on some Intel systems?  Did Intel remove this from more recent chips?

How reliable is /dev/urandom without initial entropy?  We boot from
stateless disk images and don't carry any entropy over from previous
boots.  /dev/urandom appears to be different across several servers
just after boot, but I have not found any other initialization of the
entropy pool.  I haven't checked that single systems get different
results on different boots.  I'm concerned about users getting poor
random numbers from what should be good sources.

Thanks for any suggestions,
Stuart Barkley
-- 
I've never been lost; I was once bewildered for three days, but never lost!
                                        --  Daniel Boone