[Beowulf] What services do you run on your cluster nodes?

[Prentice Bisbal]

The more services you run on your cluster node (gmond, sendmail, etc.)
the less performance is available for number crunching, but at the same
time, administration difficulty increases. For example, if you turn off
postfix/sendmail, you'll no longer get automated e-mails from your
system to alert you to a problem.

My question is this: how extreme do you go in disabling non-essential
services on your cluster nodes? Do you turn off *everything* that's not
absolutely necessary, do you leave somethings running to make
administration easier?

I'm curious to see how everyone else has their cluster(s) configured.

-- 
Prentice