Environment Variables

Inject configuration into containers with environment variables from literals, ConfigMaps, or Secrets.

Syntaxenv: - name: KEY value: "literal" - name: KEY2 valueFrom: configMapKeyRef: { name: cm, key: k }

Containers commonly read their settings from environment variables. Kubernetes gives you several sources for them under a container's env and envFrom fields.

Sources

  • Literal values — a fixed string written right in the manifest.
  • ConfigMap keys — via configMapKeyRef.
  • Secret keys — via secretKeyRef.
  • Pod fields — via fieldRef (e.g. the Pod's own name or namespace).

Bulk import

Use envFrom to pull every key from a ConfigMap or Secret at once, instead of listing them one by one.

Example

Example · yaml
apiVersion: v1
kind: Pod
metadata:
  name: env-demo
spec:
  containers:
    - name: app
      image: busybox:1.36
      command: ["sh", "-c", "env; sleep 3600"]
      env:
        - name: GREETING
          value: "hello"
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: LOG_LEVEL
          valueFrom:
            configMapKeyRef:
              name: app-config
              key: LOG_LEVEL

When to use it

  • A twelve-factor app reads all external configuration from environment variables injected by Kubernetes, keeping the image environment-agnostic.
  • A developer overrides a single environment variable in a pod spec to enable debug mode without changing the shared ConfigMap.
  • A platform team injects pod metadata like the node name and pod IP as environment variables using the Downward API so the app can include them in logs.

More examples

Static and ConfigMap env vars

Shows three env var sources in one container spec: a literal value, a ConfigMap key, and a Secret key.

Example · yaml
spec:
  containers:
    - name: app
      image: myapp:1.0
      env:
        - name: APP_ENV
          value: production
        - name: LOG_LEVEL
          valueFrom:
            configMapKeyRef:
              name: app-config
              key: LOG_LEVEL
        - name: DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: db-creds
              key: password

Downward API env vars

Uses the Downward API to inject pod metadata into the container at runtime, enabling the app to self-identify.

Example · yaml
env:
  - name: POD_NAME
    valueFrom:
      fieldRef:
        fieldPath: metadata.name
  - name: POD_NAMESPACE
    valueFrom:
      fieldRef:
        fieldPath: metadata.namespace
  - name: NODE_NAME
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName

Inspect env vars inside a pod

Runs env inside the pod to list all injected variables, and printenv to retrieve a specific one for debugging.

Example · bash
kubectl exec -it my-pod -- env | sort
# Shows all environment variables available inside the container

kubectl exec -it my-pod -- printenv DB_PASSWORD

Related

k8s configmapsk8s secrets

Discussion

  • Be the first to comment on this lesson.
Environment Variables — Kubernetes | SoundsCode