Supply Nginx Configuration Using ConfigMap¶

Now, let's see how you can use ConfigMap to supply configuration to applications. In this example, we will use ConfigMap to provide configuration to the nginx application.

Nginx Deployment Without ConfigMap¶

First, let's explore the default behaviour of nginx application.

By default, Nginx serves responses from a virtual server that listens on port 80 and serves the default index.html file located at /usr/share/nginx/html.

Let's test this out!

1. Create nginx deployment manifest¶

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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

2. Apply the manifest to create the nginx deployment¶

kubectl apply -f nginx-deployment.yml

3. Verify deployment and pods¶

# List deployments
kubectl get deployments

# List pods
kubectl get pods

4. View default 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 80 by default
• Nginx serves the default index.html page at /usr/share/nginx/html

Get response from nginx server:

# Hit port 80
curl localhost
{OR}
curl localhost:80

What if you want nginx to serve response from port 8080 instead of port 80?

ConfigMap can help. Let's try it out!

Step 1: Create a ConfigMap That Stores Nginx Configuration¶

First, let's create a ConfigMap that stores nginx configuration as follows:

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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;
      }
    }

Observe the following:

• The nginx server listens on port 8080
• Nginx will serve the default 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: Update Nginx Deployment to Use Configuration From ConfigMap¶

Let's update the nginx deployment to use nginx configuration from the ConfigMap we created in the previous step.

The updated deployment should look like the following:

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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"
      volumes:
      - name: my-volume
        configMap:
          name: nginx-configmap

Apply the manifest to update 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>

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 now listens on port 8080
• Nginx serves the default index.html page 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/