UNHEALTHY | RED HAT 8

Problem: Gremlin agent reports as unhealthy in the app.gremlin.com UI when gremlin is installed on VMs with Red Hat8 OS. 

Cause: Red hat removed certain kernel modules that were shipped OOTB in Red Hat 7. 

Resolution: check for and install these modules with the below steps: 

packages and modules to check for: iproute-tc and kernel-modules-extra(this contains the needed sch_netem module that allows for gremlin to affect the network traffic). 

1.      yum remove gremlin -y
2.      yum install iproute-tc -y (this may be installed already. If yes, just leave it)
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.