CODEWITHSUNDEEP
dockerkubernetes
Dimuthu
Dimuthu

Reputation: 8636

Kubernetes access labels from containers

When we create a yml for the replication controller, we can give labels for the pod that is being created.

apiVersion: v1
kind: ReplicationController
metadata:
  name: redis
spec:
  template:
    metadata:
      labels:
        app: redis
        tier: backend

Can the containers that reside in this pod access those label values?

Upvotes: 1

Views: 2058

Answers (2)

Yu-Ju Hong
Yu-Ju Hong

Reputation: 7337

Check out the Downward API, which allows the container to know more about itself.

Upvotes: 5

Manya Tripathi
Manya Tripathi

Reputation: 109

One way to access information of pod from inside the container is by using environment variables. The yaml file for pod is: 

apiVersion: v1
kind: Pod
metadata:
  name: pod-env
spec:
  containers:
    - name: test-container
      image: ubuntu
      command: [ "sh", "-c"]
      args:
      - while true; do
          echo -en '\n';
          printenv MY_NODE_NAME MY_POD_NAME;
          printenv MY_POD_IP 
          sleep 1000;
        done;
      env:
        - name: MY_NODE_NAME
          valueFrom:
            fieldRef:
              fieldPath: spec.nodeName
        - name: MY_POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: MY_POD_IP
          valueFrom:
            fieldRef:
              fieldPath: status.podIP
  restartPolicy: Never

The mY_POD_NAME environment variable gets its value from the pod's field spec.nodeName. Likewise we can also container's fields as values. To verify this connect to the pod using the command:

kubectl exec -it pod-env -- /bin/bash

and print the environment variable:

printenv MY_POD_NAME

Other way of passing information from pod to container is using downwardAPI : https://kubernetes.io/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/

Upvotes: 2

Related Questions