kubernetes-docs-labels
http://kubernetes.io/docs/user-guide/labels
"Labels selectors for both objects are defined in json or yaml files using maps, and only equality-based requirement selectors are supported:" ^maps
kubectl label nodes <node-name> <label-key>=<label-value> ^add-label-using-kubectl
"or restricting negative matching via exists operator: $ kubectl get pods -l 'environment,environment notin (frontend)'"