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