debugging.md

Debugging

cluster/kubectl.sh version

will try to connect to the apiserver.

Retrieving Logs

To investigate the logs of a pod, you can view the logs via cluster/kubectl.sh logs. To view the logs of virt-api, type

cluster/kubectl.sh logs virt-api -f

Sometimes a container in a pod is crashlooping because of an application error inside it. In this case, you normally can't see any logs, because the container is already gone, and so are the logs. To get the logs from the last run attempt, the --previous flag can be used. To view the logs of the container virt-api in the pod virt-api from the previous run, type

cluster/kubectl.sh logs virt-api -f -c virt-api -p

Note that you always have to select a container inside a pod for fetching old logs with the --previous flag.

Watching Events

Both, Kubernetes and KubeVirt are creating events, which can be viewed via

cluster/kubectl.sh get events --all-namespaces --watch

This way it is pretty easy to detect if a Pod or a VM got started.

Entering Containers

It can be very valuable to enter a container and do some investigations there, to see what is going wrong. In this case the kubectl exec command can be used. To enter virt-api with an interactive shell, type

cluster/kubectl.sh exec virt-api -c virt-api -i -t -- sh

Kubelet Logs

After all you might not see errors in the logs provided by Kubernetes. In that case you can take a look at the logs of the kubelet on the host where the issue is appearing. Depending on the error it is getting logged to either the system logs or to the kubelet logs, you can use the following commands to view them:

journalctl
# or
journalctl -u kubelet

References

• kubectl overview
• kubectl reference

Using a Debugger (delve)

This shows the basic principle on how remote debugging can be done.

• Add delve to the container
• Start delve on a specific port ( dlv attach <pid> --headless --listen=0.0.0.0:1234)
• Use kube-proxy to forward the port to your machine