Using the downward API in Kubernetes

Kubernetes has something called the Downward API that allows pods to get information of their own running state and then expose it as env variables (As the below example)

What is exposed

See Official Documentation for more fields

Name	Description
metadata.name	the pod's name
metadata.namespace	the pod's namespace
metadata.uid	the pod's unique ID
metadata.annotations['<KEY>']	the value of the pod's annotation named (for example, metadata.annotations['myannotation'])
metadata.labels['<KEY>']	the text value of the pod's label named (for example, metadata.labels['mylabel'])
spec.serviceAccountName	the name of the pod's service account
spec.nodeName	the name of the node where the Pod is executing
status.hostIP	the primary IP address of the node to which the Pod is assigned
status.podIP	the pod's primary IP address (usually, its IPv4 address)

Example Manifest

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - image: nginx:latest
    name: downward-test
    command:
    - my-app --pod_id=$(POD_ID) --pod_name=$(POD_NAME) --namespace_name=$(NAMESPACE_NAME)
    env:
    - name: POD_ID
      valueFrom:
        fieldRef:
          fieldPath: metadata.uid
    - name: POD_NAME
      valueFrom:
        fieldRef:
          fieldPath: metadata.name
    - name: NAMESPACE_NAME
      valueFrom:
        fieldRef:
          fieldPath: metadata.namespace

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