Configure a Pod to Use a Volume for Storage

Documentation for Kubernetes v1.10 is no longer actively maintained. The version you are currently viewing is a static snapshot. For up-to-date documentation, see the latest version.

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 metadata: name: redis spec: containers: - name: redis image: redis volumeMounts: - name: redis-storage mountPath: /data/redis volumes: - name: redis-storage emptyDir: {}`

pod-redis.yaml docs/tasks/configure-pod-container Copy pod-redis.yaml to clipboard

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: {}

Create the Pod:

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

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

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

kubectl exec -it redis – /bin/bash

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

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

In your shell, kill the redis process:

root@redis:/data/redis# kill

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

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.

Get a shell into the restarted Container:

kubectl exec -it redis – /bin/bash

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

What's next

See Volume.

See Pod.

In addition to the local disk storage provided by emptyDir, Kubernetes supports many different network-attached storage solutions, including PD on GCE and EBS on EC2, which are preferred for critical data, and will handle details such as mounting and unmounting the devices on the nodes. See Volumes for more details.

Tasks

Documentation for Kubernetes v1.10 is no longer actively maintained. The version you are currently viewing is a static snapshot. For up-to-date documentation, see the latest version.

Configure a Pod to Use a Volume for Storage

Before you begin

Configure a volume for a Pod

What's next