ConfigMaps

[!NOTE] This module explores the core principles of ConfigMaps, deriving solutions from first principles and hardware constraints to build world-class, production-ready expertise.

1. The Problem

Hardcoding configuration (DB URLs, API Keys) in container images is bad practice.

  • Rebuilds: You have to rebuild the image to change config.
  • Security: Secrets might leak.
  • Environment: Dev/Staging/Prod need different configs.

2. The Solution: ConfigMap

A key-value store for non-sensitive data. You can inject data into Pods as:

  1. Environment Variables: Good for simple flags.
  2. Files (Volume Mount): Good for nginx.conf or application.properties.

3. Interactive: Config Injection Visualizer

See how data flows from ConfigMap to Pod.

ConfigMap

DB_HOST=db.prod DEBUG=false
→

Pod (Env Vars)

DB_HOST=??? DEBUG=???

4. Code Example: Using ConfigMaps

ConfigMap
Pod (Env)
Pod (Volume)
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  # Key-Value pairs
  DB_HOST: "postgres-svc"
  LOG_LEVEL: "info"

  # File content
  nginx.conf: |
    server {
      listen 80;
    }

apiVersion: v1
kind: Pod
metadata:
  name: env-demo
spec:
  containers:
  - name: app
  image: my-app
  envFrom:
  - configMapRef:
    name: app-config

apiVersion: v1
kind: Pod
metadata:
  name: volume-demo
spec:
  containers:
  - name: nginx
  image: nginx
  volumeMounts:
  - name: config-volume
    mountPath: /etc/nginx/conf.d
  volumes:
  - name: config-volume
  configMap:
    name: app-config