k8s之emptyDir存储卷

一、简介

• emptyDir卷是最简单的卷，主要用于存储临时数据，当pod生命周期结束，emptyDir卷也就销毁。
• emptyDir卷应用场景一般是pod中多个容器共享数据，即在pod中定义一个emptyDir卷，然后容器A挂载到某个目录，容器B也挂载到某个目录，这样，容器A和容器B就能读写文件，就能共享数据。

二、存储介质

• medium:此目录所在的存储介质的类型，可用值为“default”或“Memory”。
• sizeLimit:当前存储卷的空间限额，默认值为nil，表示不限制。

三、实现emptyDir存储卷

root@k8s-master01:~/learning-k8s/examples/volumes# cat pod-with-emptyDir-vol.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pods-with-emptydir-vol
spec:
  containers:
  - image: ikubernetes/admin-box:v1.2
    name: admin
    command: ["/bin/sh", "-c"]
    args: ["sleep 99999"]
    resources: {}
    volumeMounts:
    - name: data
      mountPath: /data
  - image: ikubernetes/demoapp:v1.0
    name: demoapp
    resources: {}
    volumeMounts:
    - name: data
      mountPath: /var/www/html
  volumes:
  - name: data
    emptyDir:
      medium: Memory
      sizeLimit: 16Mi
  dnsPolicy: ClusterFirst
  restartPolicy: Always

root@k8s-master01:~/learning-k8s/examples/volumes# kubectl apply -f pod-with-emptyDir-vol.yaml 
pod/pods-with-emptydir-vol created

root@k8s-master01:~/learning-k8s/examples/volumes# kubectl get pod  
NAME                     READY   STATUS    RESTARTS   AGE
pods-with-emptydir-vol   2/2     Running   0          5m20s

四、验证容器之间的数据共享
1、进入admin容器创建test.html文件，进入dempapp容器中验证。

root@k8s-master01:~/learning-k8s/examples/volumes# kubectl exec -it pods-with-emptydir-vol -c admin bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
root@pods-with-emptydir-vol /# cd /data/
root@pods-with-emptydir-vol data# echo "<h1>Index Page</h1>" > test.html
root@pods-with-emptydir-vol data# cat test.html 
<h1>Index Page</h1>

2、在admin容器的挂载目录下生成了test.html

root@k8s-master01:~/learning-k8s/examples/volumes# kubectl exec -it pods-with-emptydir-vol -c demoapp /bin/sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
[root@pods-with-emptydir-vol /]# cd /var/www/html/
[root@pods-with-emptydir-vol /var/www/html]# ls
test.html
[root@pods-with-emptydir-vol /var/www/html]# cat test.html 
<h1>Index Page</h1>

3、同理，在demoapp创建test02在admin容器也能看到

[root@pods-with-emptydir-vol /var/www/html]# echo $(date) $(hostname)> test02.html
[root@pods-with-emptydir-vol /var/www/html]# cat test
test.html    test02.html
[root@pods-with-emptydir-vol /var/www/html]# cat test02.html 
Mon Jan 22 13:19:03 UTC 2024 pods-with-emptydir-vol
[root@pods-with-emptydir-vol /var/www/html]# exit
root@k8s-master01:~/learning-k8s/examples/volumes# kubectl exec -it pods-with-emptydir-vol -c admin bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
root@pods-with-emptydir-vol /# cd /data/
root@pods-with-emptydir-vol data# ls
test.html    test02.html
root@pods-with-emptydir-vol data# cat test02.html 
Mon Jan 22 13:19:03 UTC 2024 pods-with-emptydir-vol