Managing Kubernetes ConfigMaps and Secrets

Applications running in Kubernetes often require configuration settings such as database URLs, API keys, and environment variables. Kubernetes provides two key resources for managing this configuration data:

1. ConfigMaps – Store non-sensitive configuration data like environment variables and configuration files.
2. Secrets – Store sensitive information like passwords, tokens, and certificates securely.

What is a ConfigMap?

A ConfigMap allows you to store configuration data separately from your application code. This enables dynamic configuration updates without modifying container images.

Use Cases:

• Storing environment variables.
• Managing configuration files and command-line arguments.
• Decoupling application code from configuration.

Example: Creating a ConfigMap

Using YAML:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_ENV: "production"
  DATABASE_URL: "postgres://db-service:5432/mydb"

Apply the ConfigMap:

kubectl apply -f configmap.yaml

Using kubectl CLI:

kubectl create configmap app-config --from-literal=APP_ENV=production --from-literal=DATABASE_URL=postgres://db-service:5432/mydb

Using ConfigMap in a Pod

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
    - name: my-container
      image: nginx
      envFrom:
        - configMapRef:
            name: app-config

Verify the ConfigMap:

kubectl get configmap app-config -o yaml

What is a Secret?

A Secret is similar to a ConfigMap but is used for storing sensitive data like passwords, API keys, and certificates.

Use Cases:

• Storing database passwords securely.
• Managing API keys and tokens.
• Securing TLS certificates for encrypted communication.

Example: Creating a Secret

Using YAML (Base64 Encoded Values):

apiVersion: v1
kind: Secret
metadata:
  name: db-secret
type: Opaque
data:
  DB_USER: cG9zdGdyZXM=  # Base64 encoded "postgres"
  DB_PASSWORD: cGFzc3dvcmQ=  # Base64 encoded "password"

Apply the Secret:

kubectl apply -f secret.yaml

Using kubectl CLI:

kubectl create secret generic db-secret --from-literal=DB_USER=postgres --from-literal=DB_PASSWORD=password

Using a Secret in a Pod

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
    - name: my-container
      image: nginx
      env:
        - name: DB_USER
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: DB_USER
        - name: DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: DB_PASSWORD

Verify the Secret:

kubectl get secret db-secret -o yaml

ConfigMap vs. Secret: Key Differences

Feature ConfigMap Secret Purpose Store non-sensitive config data Store sensitive data securely Data Type Plain text Base64-encoded Security Stored as plain text in etcd Stored as base64-encoded data in etcd Access Environment variables, mounted as files Environment variables, mounted as files

Best Practices for Using ConfigMaps and Secrets

• Use ConfigMaps for non-sensitive data like application settings.
• Use Secrets for sensitive data like credentials and API keys.
• Restrict access to Secrets using Role-Based Access Control (RBAC).
• Avoid hardcoding credentials in deployment files; use Secrets instead.
• Use mounted volumes for secrets instead of environment variables when security is a concern.

Kubernetes ConfigMaps and Secrets provide a way to manage configuration and sensitive data securely and efficiently. Understanding their differences and best practices ensures better application management in Kubernetes.