[Beowulf] ganglia on CentOS 8?

[David Mathog]

Solved it.

The problem was that firewalld was running on CentOS 8.  It sets up a 
firewall but those changes are NOT visible in "iptables --list", so
I didn't know it was there until an nmap from another machine showed port 
9090 on the CentOS 8 machine.  lsof had nothing attached to 9090. This was
super confusing. It turned out that firewalld for some reason had
opened that port for "cockpit" even though that package is not only not 
running, but is not installed.  (And never was.)  Good thing that it did
so, it turns out, or I would never have started looking for _another_ 
firewall.

So the solution is to stop firewalld and then disable it.  Otherwise, add 
rules to firewalld allowing gmond/gmetad connections.  The RPMs that were
rebuilt from the Fedora src.rpm did not contain commands to set these 
rules, apparently.

Regards,

David Mathog
mathog at caltech.edu