Implement State Persistence for Kubernetes Pods

1 hour
  • 3 Learning Objectives

About this Hands-on Lab

Part of the power of Kubernetes containers comes from their ephemeral nature. They can be easily created, destroyed, and replaced, and this makes them easy to manage. However, sometimes we need to maintain persistent data that survives beyond the life of a pod. In this lab, we will go through how to implement state persistence using PersistentVolumes and PersistentVolume claims. We will create persistent storage and consume it using a pod.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create a PersistentVolume

Create a descriptor file with vi mysql-pv.yml:

kind: PersistentVolume
apiVersion: v1
metadata:
  name: mysql-pv
spec:
  storageClassName: localdisk
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"

Create the PersistentVolume.

kubectl apply -f mysql-pv.yml
Create a PersistentVolumeClaim

Create a descriptor file with vi mysql-pv-claim.yml:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  storageClassName: localdisk
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 500Mi

Create the PersistentVolumeClaim:

kubectl apply -f mysql-pv-claim.yml
Create a MySQL Pod configured to use the PersistentVolumeClaim

Create a descriptor file with vi mysql-pod.yml:

apiVersion: v1
kind: Pod
metadata:
  name: mysql-pod
spec:
  containers:
  - name: mysql
    image: mysql:5.6
    ports:
    - containerPort: 3306
    env:
    - name: MYSQL_ROOT_PASSWORD
      value: password
    volumeMounts:
    - name: mysql-storage
      mountPath: /var/lib/mysql
  volumes:
  - name: mysql-storage
    persistentVolumeClaim:
      claimName: mysql-pv-claim

Create the Pod:

kubectl apply -f mysql-pod.yml

Check the status of the pod with kubectl get pod mysql-pod. After a few moments it should be in the RUNNING status.

You can also verify that the pod is interacting with the filesystem at /mnt/data on the node. Log in to the node from the Kube master like this, using the same as the password for the kube master:

ssh cloud_user@10.0.1.102

Check the contents of the PersistentVolume directory:

ls /mnt/data

You should see files and directories there related to MySQL. These were created by the pod, meaning that your PersistentVolume and PersistentVolumeClaim are working!

Additional Resources

Your company needs a small database server to support a new application. They have asked you to deploy a pod running a MySQL container, but they want the data to persist even if the pod is deleted or replaced. Therefore, the MySQL database pod requires persistent storage.

You will need to do the following:

  1. Create a PersistentVolume:
    • The PersistentVolume should be named mysql-pv.
    • The volume needs a capacity of 1Gi.
    • Use a storageClassName of localdisk.
    • Use the accessMode ReadWriteOnce.
    • Store the data locally on the node using a hostPath volume at the location /mnt/data.
  2. Create a PersistentVolumeClaim:
    • The PersistentVolumeClaim should be named mysql-pv-claim.
    • Set a resource request on the claim for 500Mi of storage.
    • Use the same storageClassName and accessModes as the PersistentVolume so that this claim can bind to the PersistentVolume.
  3. Create a MySQL Pod configured to use the PersistentVolumeClaim:
    • The Pod should be named mysql-pod.
    • Use the image mysql:5.6.
    • Expose the containerPort 3306.
    • Set an environment variable called MYSQL_ROOT_PASSWORD with the value password.
    • Add the PersistentVolumeClaim as a volume and mount it to the container at the path /var/lib/mysql.

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