Supply Multiple Nginx Configuration Using ConfigMap¶

In the previous lesson, we learned how to use a ConfigMap to supply nginx configuration file to nginx. More specifically, we used a ConfigMap to modify the default nginx port.

In this example, we will explore how to use a ConfigMap to supply multiple nginx configuration files. Specifically, we will learn how to use a ConfigMap to modify the default nginx port and serve a custom HTML page.

Step 1: Create a ConfigMap That Stores Nginx Configuration¶

Let's create a ConfigMap that stores nginx configuration:

nginx-configmap.yml

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-configmap
data:
  default.conf: |
    server {
      listen       8080;
      listen  [::]:8080;
      server_name  localhost;

      #access_log  /var/log/nginx/host.access.log  main;

      location / {
          root   /usr/share/nginx/html;
          index  index.html index.htm;
      }

      #error_page  404              /404.html;

      # redirect server error pages to the static page /50x.html
      #
      error_page   500 502 503 504  /50x.html;
      location = /50x.html {
          root   /usr/share/nginx/html;
      }
    }
  index.html: |
    <!DOCTYPE html>
      <html>
        <head>
          <title>Welcome to My Website!</title>
        </head>
        <body>
          <h1>Welcome to My Website!</h1>
        </body>
    </html>

Observe the following:

The nginx server listens on port 8080
Nginx will serve the modified index.html page at /usr/share/nginx/html

Apply the manifest to create ConfigMap:

kubectl apply -f nginx-configmap.yml

Step 2: Verify ConfigMap¶

# List configmaps
kubectl get cm

# Describe the configmap
kubectl describe cm nginx-configmap

Step 3: Create Nginx Deployment That Uses Configuration from ConfigMap¶

Let's create nginx deployment that uses configuration files from the ConfigMap we created in the previous step:

nginx-deployment.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        volumeMounts:
        - name: my-volume
          mountPath: "/etc/nginx/conf.d/default.conf"
          subPath: "default.conf"
        - name: my-volume
          mountPath: "/usr/share/nginx/html/index.html"
          subPath: "index.html"
      volumes:
      - name: my-volume
        configMap:
          name: nginx-configmap

Observe the following:

We have created a volume from nginx-configmap ConfigMap
We have mounted default.conf file from nginx-configmap to the nginx container at /etc/nginx/conf.d/default.conf
We have mounted index.html file from nginx-configmap to the nginx container at /usr/share/nginx/html/index.html

Note

By using subPath to specify the specific file within the ConfigMap volume, we can selectively mount only the necessary configuration files or data that a container needs.

Apply the manifest to create the deployment:

kubectl apply -f nginx-deployment.yml

Step 4: Verify Deployment and Pods¶

# List deployments
kubectl get deployments

# List pods
kubectl get pods

# Describe the Pod
kubectl describe pod <pod-name>

Observe the Mounts field of the nginx container. You'll see 2 mounts from my-volume.

Step 5: View Nginx Configuration Files¶

# Start a shell session inside the container
kubectl exec -it <pod-name> -- bash

# View the content of the default.conf file
cat /etc/nginx/conf.d/default.conf

# View the content of the default web pages
cd /usr/share/nginx/html
ls
cat index.html

Observe the following:

The nginx server listens on port 8080
Nginx serves the supplied index.html page mounted at /usr/share/nginx/html

Get response from nginx server:

# Hit port 8080
curl localhost:8080

Clean Up¶

Assuming your folder structure looks like the one below:

|-- manifests
│   |-- nginx-deployment.yml
│   |-- nginx-configmap.yml

Let's delete all the resources we created:

kubectl delete -f manifests/