Use ConfigMap as Volume¶

Let's see how we can use ConfigMap as a volume and mount it in a container.

Step 1: Create a ConfigMap¶

my-configmap.yml

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-configmap
data:
  # property-like keys; each key maps to a simple value
  foo1: bar1
  foo2: bar2

  # file-like keys; each key maps to a file content
  game.properties: |
    enemy.types=aliens,monsters
    player.maximum-lives=5    
  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;
      }
    }

Apply the manifest to create ConfigMap:

kubectl apply -f my-configmap.yml

Step 2: Verify ConfigMap¶

# List configmaps
kubectl get cm

# Describe the configmap
kubectl describe cm my-configmap

Step 3: Create Pods That Uses ConfigMap as Volume¶

Let's create pods that uses ConfigMap as volume and mounts it in a container. We'll use a deployment to create pods:

my-deployment.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        volumeMounts:
        - name: my-volume
          mountPath: "/config"
      volumes:
      - name: my-volume
        configMap:
          name: my-configmap

Observe the following:

The pod uses the ConfigMap my-configmap as volume
The volume is mounted at /config directory in the nginx container

Apply the manifest to create deployment:

kubectl apply -f my-deployment.yml

Step 4: Verify Deployment and Pods¶

# List deployments
kubectl get deployments

# List pods
kubectl get pods

Step 5: Verify Volume Mount and Data¶

Open a shell session inside the nginx container:
```
kubectl exec -it <pod-name> -- bash
```
View data:
```
cd /config
ls
```

Please note that when a ConfigMap is mounted as a volume in a container, each key in the ConfigMap is stored as a file in the container's file system. This means that the container can read the contents of each file as if they were regular files in the container's file system.

Clean Up¶

Assuming your folder structure looks like the one below:

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

Let's delete all the resources we created:

kubectl delete -f manifests/