Day 54beginnerMar 26, 2026

Load Config Files into Pods with ConfigMap

ConfigMaps decouple configuration from images so you can change settings without rebuilding.

kubernetesconfigurationpods

What

ConfigMaps let you decouple configuration from container images. You can create them from files, directories, or literal key-value pairs, then mount them as volumes inside pods or expose them as environment variables. This means the same container image works across dev, staging, and production with different configs.

Why It Matters

Hardcoding configuration into container images means you need to rebuild and redeploy every time a setting changes. ConfigMaps separate config from code, letting you update database URLs, feature flags, or application settings without touching your image. This is a core principle of twelve-factor app design.

Example

# Create a ConfigMap from a file
kubectl create configmap app-config --from-file=config.yaml

# Create from literal values
kubectl create configmap app-settings \
  --from-literal=DB_HOST=postgres.default.svc \
  --from-literal=LOG_LEVEL=info

# Mount ConfigMap as a volume in a Pod
apiVersion: v1
kind: Pod
metadata:
  name: my-app
spec:
  containers:
  - name: app
    image: myapp:latest
    volumeMounts:
    - name: config-volume
      mountPath: /etc/config
  volumes:
  - name: config-volume
    configMap:
      name: app-config

# View ConfigMap contents
kubectl get configmap app-config -o yaml

yaml

Common Mistake

Updating a ConfigMap and expecting running pods to pick up the changes automatically. Pods that mount ConfigMaps as volumes will eventually see updates (with a delay), but pods using environment variables from ConfigMaps will NOT update until they are restarted.

Quick Fix

After updating a ConfigMap, restart your deployment with `kubectl rollout restart deployment/<name>`. For automatic reloads, use a tool like Reloader (stakater/Reloader) that watches ConfigMaps and triggers rolling restarts when they change.