K8s-Configmap.md

LAB: K8s Configmap

This scenario shows:

• how to create config map (declerative way),
• how to use configmap: volume and environment variable,
• how to create configmap with command (imperative way),
• how to get/delete configmap

Steps

• Run minikube (in this scenario, K8s runs on WSL2- Ubuntu 20.04) ("minikube start")

• Create Yaml file (config.yaml) in your directory and copy the below definition into the file:

apiVersion: v1
kind: ConfigMap
metadata:
  name: myconfigmap               
data:
  db_server: "db.example.com"        # configmap key-value parameters
  database: "mydatabase"
  site.settings: |
    color=blue
    padding:25px
---
apiVersion: v1
kind: Pod
metadata:
  name: configmappod
spec:
  containers:
  - name: configmapcontainer
    image: nginx
    env:                             # configmap using environment variable
      - name: DB_SERVER
        valueFrom:
          configMapKeyRef:           
            name: myconfigmap        # configmap name, from "myconfigmap" 
            key: db_server
      - name: DATABASE
        valueFrom:
          configMapKeyRef:
            name: myconfigmap
            key: database
    volumeMounts:
      - name: config-vol
        mountPath: "/config"
        readOnly: true
  volumes:
    - name: config-vol               # transfer configmap parameters using volume
      configMap:
        name: myconfigmap

• Create configmap and the pod:

• Run bash in the pod:

• Define configmap with imperative way (--from-file and --from-literal) (create a file and put into "theme=dark")

kubectl create configmap myconfigmap2 --from-literal=background=red --from-file=theme.txt

• Delete configmap: