Unable to get metrics from node_exporter

[chlung]

Hi,
I am building custom metrics server by following this github instructions. Thanks. It works. Now, I would like to deploy node_exporter from https://github.com/coreos/prometheus-operator/tree/master/contrib/kube-prometheus/manifests/node-exporter to get node level information, but I don't see any metrics from node_exporter , such as node_memory_MemFree or node_memory_MemTotal, when I invoked kubectl get --raw /metrics. Do I need any additional components?

Thanks.