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ConfigMap

How does a ConfigMap work?

ConfigMap

A ConfigMap is a dictionary of key-value pairs that store configuration settings for your applications.

First, create a ConfigMap in your cluster by tweaking our sample YAML to your needs.

Second, consume to ConfigMap in your Pods and use its values.

The ConfigMap described in nginx-cm.yaml bring two key/value entry, the first nginx.conf will be used within a Nginx container to configure the webserver, the second virtualhost.conf will be used to configure a Virtualhost within the same Nginx container.

To understand better how ConfigMaps are declared, please have a look of nginx-cm.yaml file.

Let's create the CM

$ kubectl apply -f nginx-cm.yaml
configmap/nginx-conf created

With the following instructions, the Nginx container uses the CM key/value entries to configure Nginx webserver:

...
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: /etc/nginx # mount nginx-conf volume to /etc/nginx
          readOnly: true
          name: nginx-conf
        - mountPath: /var/log/nginx
          name: log
      volumes:
      - name: nginx-conf
        configMap:
          name: nginx-conf # place ConfigMap `nginx-conf` on /etc/nginx
          items:
            - key: nginx.conf
              path: nginx.conf
            - key: virtualhost.conf
              path: virtualhost/virtualhost.conf # dig directory
      - name: log
        emptyDir: {}
...

Let's create the Nginx Pod

$ kubectl apply -f nginx-deployment.yaml
deployment.apps/nginx created

Verify that the Pod is running

$ kubectl get po 
NAME                     READY   STATUS    RESTARTS   AGE
nginx-5496c46599-k5wzd   1/1     Running   0          21s

The Nginx container has been configured (through the ConfigMap) to proxy requests to http://www.sunnyvale.it website.

To test our Nginx configuration let's create a NodePort service

$ kubectl apply -f nginx-service.yaml 
service/nginx created

If everything has been configured properly, if you point your browser to http://localhost:31719 you should be redirected to http://www.sunnyvale.it website.

To remove everything you created earlier:

$ kubectl delete -f .
configmap "nginx-conf" deleted
deployment.apps "nginx" deleted
service "nginx" deleted