146 lines
4.0 KiB
Markdown
146 lines
4.0 KiB
Markdown
---
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title: Configure a Pod to Use a Volume for Storage
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content_template: templates/task
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weight: 50
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---
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{{% capture overview %}}
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This page shows how to configure a Pod to use a Volume for storage.
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A Container's file system lives only as long as the Container does. So when a
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Container terminates and restarts, filesystem changes are lost. For more
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consistent storage that is independent of the Container, you can use a
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[Volume](/docs/concepts/storage/volumes/). This is especially important for stateful
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applications, such as key-value stores (such as Redis) and databases.
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{{% /capture %}}
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{{% capture prerequisites %}}
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{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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{{% /capture %}}
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{{% capture steps %}}
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## Configure a volume for a Pod
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In this exercise, you create a Pod that runs one Container. This Pod has a
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Volume of type
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[emptyDir](/docs/concepts/storage/volumes/#emptydir)
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that lasts for the life of the Pod, even if the Container terminates and
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restarts. Here is the configuration file for the Pod:
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{{< codenew file="pods/storage/redis.yaml" >}}
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1. Create the Pod:
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```shell
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kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml
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```
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1. Verify that the Pod's Container is running, and then watch for changes to
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the Pod:
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```shell
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kubectl get pod redis --watch
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```
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The output looks like this:
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```shell
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NAME READY STATUS RESTARTS AGE
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redis 1/1 Running 0 13s
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```
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1. In another terminal, get a shell to the running Container:
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```shell
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kubectl exec -it redis -- /bin/bash
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```
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1. In your shell, go to `/data/redis`, and then create a file:
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```shell
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root@redis:/data# cd /data/redis/
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root@redis:/data/redis# echo Hello > test-file
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```
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1. In your shell, list the running processes:
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```shell
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root@redis:/data/redis# apt-get update
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root@redis:/data/redis# apt-get install procps
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root@redis:/data/redis# ps aux
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```
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The output is similar to this:
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```shell
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USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
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redis 1 0.1 0.1 33308 3828 ? Ssl 00:46 0:00 redis-server *:6379
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root 12 0.0 0.0 20228 3020 ? Ss 00:47 0:00 /bin/bash
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root 15 0.0 0.0 17500 2072 ? R+ 00:48 0:00 ps aux
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```
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1. In your shell, kill the Redis process:
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```shell
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root@redis:/data/redis# kill <pid>
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```
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where `<pid>` is the Redis process ID (PID).
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1. In your original terminal, watch for changes to the Redis Pod. Eventually,
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you will see something like this:
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```shell
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NAME READY STATUS RESTARTS AGE
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redis 1/1 Running 0 13s
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redis 0/1 Completed 0 6m
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redis 1/1 Running 1 6m
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```
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At this point, the Container has terminated and restarted. This is because the
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Redis Pod has a
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[restartPolicy](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#podspec-v1-core)
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of `Always`.
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1. Get a shell into the restarted Container:
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```shell
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kubectl exec -it redis -- /bin/bash
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```
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1. In your shell, go to `/data/redis`, and verify that `test-file` is still there.
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```shell
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root@redis:/data/redis# cd /data/redis/
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root@redis:/data/redis# ls
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test-file
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```
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1. Delete the Pod that you created for this exercise:
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```shell
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kubectl delete pod redis
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```
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{{% /capture %}}
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{{% capture whatsnext %}}
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* See [Volume](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#volume-v1-core).
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* See [Pod](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#pod-v1-core).
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* In addition to the local disk storage provided by `emptyDir`, Kubernetes
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supports many different network-attached storage solutions, including PD on
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GCE and EBS on EC2, which are preferred for critical data and will handle
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details such as mounting and unmounting the devices on the nodes. See
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[Volumes](/docs/concepts/storage/volumes/) for more details.
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{{% /capture %}}
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