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 gremlin gremlind -y
5. modprobe sch_netem
6. gremlin attack cpu -l 30 (document any errors)
7. gremlin attack latency -l 30 (document any errors)
8. if there is a qdisc error, reboot the server and repeat step 5.
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