ConfigMaps

Relax. We'll talk through this in plain words — no textbook voice.

What you'll walk away with

Understand ConfigMaps without any of the intimidation
Get comfortable running kubectl commands and YAML yourself
Apply this concept right away in a real project

Take a moment to think about this

If you hardcode a config value (say `API_URL=https://staging.example.com`) into your Docker image, moving from staging to production means rebuilding the image — that's slow and error-prone. With a ConfigMap, you keep the config value as a separate Kubernetes object, and your Pod injects it at run time as an environment variable (or a file) — you can change app behavior just by changing the ConfigMap, without touching the image itself.

Let's connect this to a real scenario

You define a ConfigMap in YAML and pull it into your Pod spec with `envFrom` (all its key-value pairs as env variables) or `volumeMounts` (as a config file). You can keep separate ConfigMaps for staging and production and switch environments just by swapping the ConfigMap, without ever touching the Deployment YAML.

ConfigMap = storing config data outside the container image
Can be injected into a Pod as environment variables or as a file
For sensitive data (passwords, API keys), use a Secret instead of a ConfigMap (covered next lesson)

Let's look at it together

yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  API_URL: "https://api.example.com"
  LOG_LEVEL: "info"
---
apiVersion: v1
kind: Pod
metadata:
  name: app-with-config
spec:
  containers:
    - name: app
      image: my-app:latest
      envFrom:
        - configMapRef:
            name: app-config

You should see

$ kubectl exec app-with-config -- printenv API_URL
https://api.example.com

5-minute try-it

Create a ConfigMap and hook it up to a Pod using envFrom — verify the value showed up with `kubectl exec <pod> -- printenv`.

A quick word of caution

Anyone can read a ConfigMap's data with `kubectl get configmap -o yaml` — never put any sensitive data in a ConfigMap.

Easy traps

Putting passwords/API keys into a ConfigMap — data in a ConfigMap is plain text, not encrypted (use a Secret instead)
Assuming an updated ConfigMap value shows up instantly without restarting the Pod — if you're using envFrom, the Pod needs to be recreated/restarted before it picks up the new value

Now try it yourself

Create a ConfigMap and hook it up to a Pod using envFrom — verify the value showed up with `kubectl exec <pod> -- printenv`.

You'll know it worked when: $ kubectl exec app-with-config -- printenv API_URL https://api.example.com