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Configure a Pod to Use a Volume for Storage

This page shows how to configure a Pod to use a Volume for storage.

A Container’s file system lives only as long as the Container does, so when a Container terminates and restarts, changes to the filesystem are lost. For more consistent storage that is independent of the Container, you can use a Volume. This is especially important for stateful applications, such as key-value stores and databases. For example, Redis is a key-value cache and store.

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:

To check the version, enter kubectl version.

Configure a volume for a Pod

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:

pod-redis.yaml docs/tasks/configure-pod-container
apiVersion: v1
kind: Pod
  name: redis
  - name: redis
    image: redis
    - name: redis-storage
      mountPath: /data/redis
  - name: redis-storage
    emptyDir: {}
  1. Create the Pod:

    kubectl create -f https://k8s.io/docs/tasks/configure-pod-container/pod-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 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# 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

    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.

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