When running on Kubernetes, you might need to troubleshoot a Node Exporter pod, and for that you're required to know on which host it's running. Node Exporter metrics see the pod and not the host, so you don't have the hostname available in the metrics that produced. In this scenario, we are required to add the missing information to metrics that didn't have that label originally. Another alternative to this scenario would be to make the required information available in the instance labels via relabeling.