CKAD_Configuring a Pod to Use a ConfigMap

Configuring a Pod to Use a ConfigMap

1. Create a new file named config.txt with the following environment variables as key/value pairs on each line.

• DB_URL equates to localhost:3306
• DB_USERNAME equates to postgres

1. Create a new ConfigMap named db-config from that file.
2. Create a Pod named backend that uses the environment variables from the ConfigMap and runs the container with the image nginx.
3. Shell into the Pod and print out the created environment variables. You should find DB_URL and DB_USERNAME with their appropriate values.

1.Create a new file named config.txt with the following environment variables as key/value pairs on each line.

可使用echo

 echo -e "DB_URL=localhost:3306\nDB_USERNAME=postgres" > config.txt

-e為 使得 echo 命令將 \n 解釋為換行符

或是 printf

printf "DB_URL=localhost:3306\nDB_USERNAME=postgres\n" > config.txt

2.Create a new ConfigMap named db-config from that file.

使用 create configmap

kubectl create configmap db-config --from-file=config.txt

3.Create a Pod named backend that uses the environment variables from the ConfigMap and runs the container with the image nginx.

kubectl run backend --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml

• kubectl run backend: 使用 kubectl run 命令創建一個名為 "backend" 的新 Pod。
• --image=nginx: 指定 Pod 使用 "nginx" 鏡像。
• --restart=Never: 設置 Pod 的重啟策略為 "Never"，即當 Pod 終止後不會自動重新啟動。
• -o yaml: 指定將生成的 Pod 配置以 YAML 格式輸出。
• --dry-run=client: 使用 --dry-run=client 選項進行模擬操作，不會對實際的集群進行任何更改。
• > pod.yaml: 將輸出的 YAML 配置重定向到名為 "pod.yaml" 的文件中，而不是輸出到終端。

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: backend
  name: backend
spec:
  containers:
  - image: nginx
    name: backend
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

產生的yaml

增加
envFrom:
— configMapRef:
name: db-config

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: backend
  name: backend
spec:
  containers:
  - image: nginx
    name: backend
    envFrom:
      - configMapRef:
          name: db-config
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

產生出的configMap

Create the Pod by pointing the create command to the YAML file.

$ kubectl create -f pod.yaml

Log into the Pod and run the env command.

kubectl exec backend -it -- /bin/sh

進入pod內輸入env 查詢環境變數

可以找到DB_URL 跟 DB_USERNAME