Configure a Pod to Use a Volume for Storage

In this exercise, you create a Pod that runs one Container. This Pod has a Volume of type emptyDir that lasts for the life of the Pod, even if the Container terminates and restarts. Here is the configuration file for the Pod:

apiVersion: v1
kind: Pod
metadata:
  name: redis
spec:
  containers:
  - name: redis
    image: redis
    volumeMounts:
    - name: redis-storage
      mountPath: /data/redis
  volumes:
  - name: redis-storage
    emptyDir: {}

1. Create the Pod:

   kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml

2. Verify that the Pod’s Container is running, and then watch for changes to the Pod:

   kubectl get pod redis --watch

   The output looks like this:

   NAME      READY     STATUS    RESTARTS   AGE
   redis     1/1       Running   0          13s

3. In another terminal, get a shell to the running Container:

   kubectl exec -it redis -- /bin/bash

4. In your shell, go to /data/redis, and then create a file:

   root@redis:/data# cd /data/redis/
   root@redis:/data/redis# echo Hello > test-file

5. In your shell, list the running processes:

   root@redis:/data/redis# apt-get update
   root@redis:/data/redis# apt-get install procps
   root@redis:/data/redis# ps aux

   The output is similar to this:

   USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
   redis        1  0.1  0.1  33308  3828 ?        Ssl  00:46   0:00 redis-server *:6379
   root        12  0.0  0.0  20228  3020 ?        Ss   00:47   0:00 /bin/bash
   root        15  0.0  0.0  17500  2072 ?        R+   00:48   0:00 ps aux

6. In your shell, kill the Redis process:

   root@redis:/data/redis# kill <pid>

   where <pid> is the Redis process ID (PID).

7. In your original terminal, watch for changes to the Redis Pod. Eventually, you will see something like this:

   NAME      READY     STATUS     RESTARTS   AGE
   redis     1/1       Running    0          13s
   redis     0/1       Completed  0         6m
   redis     1/1       Running    1         6m

At this point, the Container has terminated and restarted. This is because the Redis Pod has a restartPolicy of Always.

1. Get a shell into the restarted Container:

   kubectl exec -it redis -- /bin/bash

2. In your shell, goto /data/redis, and verify that test-file is still there.

   root@redis:/data/redis# cd /data/redis/
   root@redis:/data/redis# ls
   test-file

3. Delete the Pod that you created for this exercise:

   kubectl delete pod redis

後按:

emptyDir 是一種在pod達立的時候便會出現的儲存點，就如其名，它剛開始時空白沒有任何東西。Pod中的所有Container都能夠讀寫內裡的檔案，所以emptyDir有以下用途:

1. 暫存空間

2. Container的共用空間