OpenShift Downward API Operations

Internal

• OpenShift Operations
• Downward API

Expose OpenShift Information to Pod via Environment Variables

Edit the deployment configuration for the pod we want to expose data to:

oc edit dc/<dc-name>

Add the following environment entires:

...
spec:
  ...
  template:
    ...
    spec:
      containers:
      - name: printenv
        env:
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace

The deployment configuration will produce a pod that contains the following environment properties in its environment:

POD_NAME=printenv-3-cm34t
POD_NAMESPACE=lab4

This can be verifying by oc rsh into the pod and executing "printenv".

Expose OpenShift Information to Pod via Volumes

Edit the deployment configuration for the pod we want to expose data to:

oc edit dc/<dc-name>

Add the following environment entires:

...
spec:
  ...
  template:
    ...
    spec:
      containers:
      - name: printenv
        volumeMounts:
        - name: downward-api-volume
          mountPath: /downward-info
          readOnly: false
      ...
      volumes:
      - name: downward-api-volume
        metadata:
           items:
           - name: "pod-name"
             fieldRef:
               fieldPath: metadata.name
           - name: "pod-namespace"
             fieldRef:
               fieldPath: metadata.namespace
           - name: "pod-label"
             fieldRef:
               fieldPath: metadata.labels
           - name: "pod-annotations"
             fieldRef:
               fieldPath: metadata.annotations

The deployment configuration will produce a pod will mount a /downward-info volume, which contains four files:

pod-name:

printenv-3-tm5m4

pod-namespace:

lab4

pod-label:

app="printenv"
deployment="printenv-3"
deploymentconfig="printenv"

pod-annotations:

kubernetes.io/config.seen="2017-11-22T20:53:05.131680613-08:00"
kubernetes.io/config.source="api"
kubernetes.io/created-by="{\"kind\":\"SerializedReference\",\"apiVersion\":\"v1\",\"reference\":{\"kind\":\"ReplicationController\",\"namespace\":\"lab4\",\"name\":\"printenv-3\",\"uid\":\"2dc22525-d00a-11e7-947c-525400360e56\",\"apiVersion\":\"v1\",\"resourceVersion\":\"517382\"}}\n"
openshift.io/deployment-config.latest-version="3"
openshift.io/deployment-config.name="printenv"
openshift.io/deployment.name="printenv-3"
openshift.io/generated-by="OpenShiftNewApp"
openshift.io/scc="restricted"