Gremlin Agents on RHEL8 Reporting as Unhealthy After Fresh Install

Problem: Gremlin agent reports as unhealthy in the app.gremlin.com UI when gremlin is installed on RHEL8.

Cause: Red hat removed certain kernel modules and packages (iproute-tc and kernel-modules-extra, which contains the required sch_netem module that facilitates network attacks) that were part of the core package selection in RHEL7. 

Resolution: Install the required packages via the following steps.

1.      yum remove gremlin -y
2.      yum install iproute-tc -y 
3.      yum install kernel-modules-extra -y ( this may be installed already. just leave it.)
4.      yum install kernel-modules-extra-$(uname -r) -y  ( this may be installed already. just leave it.)
5.      yum install gremlin gremlind -y
6.      modprobe sch_netem
7.      gremlin attack cpu -l 30 (document any errors)
8.      gremlin attack latency -l 30 (document any errors)
9.      if there is a qdisc error, reboot the server and repeat step 5.