luc.run

Exercise

Create a ConfigMap named mycfg containing the key pairs token=12345 and level=debug
Use the jsonpath output format to only get the content of the data key
Create a pod named demo1 with a container based on nginx:1.20, making sure each piece of data of the ConfigMap is available in the container as an environment variable of the same name
Run a shell in the nginx container and verify both environment variables are present
Create a pod named demo2 with a container based on nginx:1.20, make sure the content of the ConfigMap is available in files in /etc/app_cfg
Run a shell in the nginx container of pod demo2 and verify the content of /etc/app_cfg
Delete the ConfigMap and the pods

Documentation

https://kubernetes.io/docs/concepts/configuration/configmap/

Solution

Create a ConfigMap named mycfg containing the key pairs token=12345 and level=debug

k create configmap mycfg --from-literal=token=12345 --from-literal=level=debug

Use the jsonpath output format to only get the content of the data key

k get cm mycfg -o jsonpath={.data}

Create a pod named demo1 with a container based on nginx:1.20, making sure each piece of data of the ConfigMap is available in the container as an environment variable of the same name

k run demo1 --image=nginx:1.20 --dry-run=client -o yaml > demo1.yaml

Edit the specification so it defines the environment variables coming from the ConfigMap:

apiVersion: v1
kind: pod
metadata:
  labels:
    run: demo1
  name: demo1
spec:
  containers:
  - image: nginx:1.20
    name: demo1
    env:
    - name: token
      valueFrom:
        configMapKeyRef:
          name: mycfg
          key: token
    - name: level
      valueFrom:
        configMapKeyRef:
          name: mycfg
          key: level

Create the pod:

k apply -f demo1.yaml

Run a shell in the nginx container and verify both environment variables are present

k exec demo1 -- env
...
token=12345
level=debug

Create a pod named demo2 with a container based on nginx:1.20, make sure the content of the ConfigMap is available in files in /etc/app_cfg

k run demo2 --image=nginx:1.20 --dry-run=client -o yaml > demo2.yaml

Edit the specification so it defines a volume based on the mycfg ConfigMap and mount the content in the nginx container’s filesystem:

apiVersion: v1
kind: pod
metadata:
  labels:
    run: demo2
  name: demo2
spec:
  containers:
  - image: nginx:1.20
    name: demo2
    volumeMounts:
    - name: cfg
      mountPath: /etc/app_cfg
  volumes:
  - name: cfg
    configMap:
      name: mycfg

Create the pod:

k apply -f demo2.yaml

Run a shell in the nginx container of pod demo2 and verify the content of /etc/app_cfg

k exec demo2 -- cat /etc/app_cfg/level
debug

k exec demo2 -- cat /etc/app_cfg/token
12345

Delete the ConfigMap and the pods

k delete cm/mycfg pod/demo1 pod/demo2