Example: Deploying WordPress and MySQL with Persistent Volumes

This tutorial shows you how to deploy a WordPress site and a MySQL database using Minikube. Both applications use PersistentVolumes and PersistentVolumeClaims to store data.

A PersistentVolume (PV) is a piece of storage in the cluster that has been manually provisioned by an administrator, or dynamically provisioned by Kubernetes using a StorageClass. A PersistentVolumeClaim (PVC) is a request for storage by a user that can be fulfilled by a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods.

Objectives

• Create PersistentVolumeClaims and PersistentVolumes
• Create a kustomization.yaml with
  • a Secret generator
  • MySQL resource configs
  • WordPress resource configs
• Apply the kustomization directory by kubectl apply -k ./
• Clean up

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

• Killercoda
• Play with Kubernetes

The example shown on this page works with kubectl 1.27 and above.

Download the following configuration files:

1. mysql-deployment.yaml

2. wordpress-deployment.yaml

Create PersistentVolumeClaims and PersistentVolumes

MySQL and Wordpress each require a PersistentVolume to store data. Their PersistentVolumeClaims will be created at the deployment step.

Many cluster environments have a default StorageClass installed. When a StorageClass is not specified in the PersistentVolumeClaim, the cluster's default StorageClass is used instead.

When a PersistentVolumeClaim is created, a PersistentVolume is dynamically provisioned based on the StorageClass configuration.

Create a kustomization.yaml

Add a Secret generator

A Secret is an object that stores a piece of sensitive data like a password or key. Since 1.14, kubectl supports the management of Kubernetes objects using a kustomization file. You can create a Secret by generators in kustomization.yaml.

Add a Secret generator in kustomization.yaml from the following command. You will need to replace YOUR_PASSWORD with the password you want to use.

cat <<EOF >./kustomization.yaml secretGenerator: - name: mysql-pass  literals:  - password=YOUR_PASSWORD EOF

Add resource configs for MySQL and WordPress

The following manifest describes a single-instance MySQL Deployment. The MySQL container mounts the PersistentVolume at /var/lib/mysql. The MYSQL_ROOT_PASSWORD environment variable sets the database password from the Secret.

application/wordpress/mysql-deployment.yaml

apiVersion:v1kind:Servicemetadata:name:wordpress-mysqllabels:app:wordpressspec:ports:- port:3306selector:app:wordpresstier:mysqlclusterIP:None---apiVersion:v1kind:PersistentVolumeClaimmetadata:name:mysql-pv-claimlabels:app:wordpressspec:accessModes:- ReadWriteOnceresources:requests:storage:20Gi---apiVersion:apps/v1kind:Deploymentmetadata:name:wordpress-mysqllabels:app:wordpressspec:selector:matchLabels:app:wordpresstier:mysqlstrategy:type:Recreatetemplate:metadata:labels:app:wordpresstier:mysqlspec:containers:- image:mysql:8.0name:mysqlenv:- name:MYSQL_ROOT_PASSWORDvalueFrom:secretKeyRef:name:mysql-passkey:password- name:MYSQL_DATABASEvalue:wordpress- name:MYSQL_USERvalue:wordpress- name:MYSQL_PASSWORDvalueFrom:secretKeyRef:name:mysql-passkey:passwordports:- containerPort:3306name:mysqlvolumeMounts:- name:mysql-persistent-storagemountPath:/var/lib/mysqlvolumes:- name:mysql-persistent-storagepersistentVolumeClaim:claimName:mysql-pv-claim

The following manifest describes a single-instance WordPress Deployment. The WordPress container mounts the PersistentVolume at /var/www/html for website data files. The WORDPRESS_DB_HOST environment variable sets the name of the MySQL Service defined above, and WordPress will access the database by Service. The WORDPRESS_DB_PASSWORD environment variable sets the database password from the Secret kustomize generated.

application/wordpress/wordpress-deployment.yaml

apiVersion:v1kind:Servicemetadata:name:wordpresslabels:app:wordpressspec:ports:- port:80selector:app:wordpresstier:frontendtype:LoadBalancer---apiVersion:v1kind:PersistentVolumeClaimmetadata:name:wp-pv-claimlabels:app:wordpressspec:accessModes:- ReadWriteOnceresources:requests:storage:20Gi---apiVersion:apps/v1kind:Deploymentmetadata:name:wordpresslabels:app:wordpressspec:selector:matchLabels:app:wordpresstier:frontendstrategy:type:Recreatetemplate:metadata:labels:app:wordpresstier:frontendspec:containers:- image:wordpress:6.2.1-apachename:wordpressenv:- name:WORDPRESS_DB_HOSTvalue:wordpress-mysql- name:WORDPRESS_DB_PASSWORDvalueFrom:secretKeyRef:name:mysql-passkey:password- name:WORDPRESS_DB_USERvalue:wordpressports:- containerPort:80name:wordpressvolumeMounts:- name:wordpress-persistent-storagemountPath:/var/www/htmlvolumes:- name:wordpress-persistent-storagepersistentVolumeClaim:claimName:wp-pv-claim

1. Download the MySQL deployment configuration file.

   curl -LO https://k8s.io/examples/application/wordpress/mysql-deployment.yaml 

2. Download the WordPress configuration file.

   curl -LO https://k8s.io/examples/application/wordpress/wordpress-deployment.yaml 

3. Add them to kustomization.yaml file.

   cat <<EOF >>./kustomization.yaml resources:  - mysql-deployment.yaml  - wordpress-deployment.yaml EOF

Apply and Verify

The kustomization.yaml contains all the resources for deploying a WordPress site and a MySQL database. You can apply the directory by

kubectl apply -k ./ 

Now you can verify that all objects exist.

1. Verify that the Secret exists by running the following command:

   kubectl get secrets 

   The response should be like this:

   NAME TYPE DATA AGE mysql-pass-c57bb4t7mf Opaque 1 9s 

2. Verify that a PersistentVolume got dynamically provisioned.

   kubectl get pvc 

   Note: It can take up to a few minutes for the PVs to be provisioned and bound.

   The response should be like this:

   NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE mysql-pv-claim Bound pvc-8cbd7b2e-4044-11e9-b2bb-42010a800002 20Gi RWO standard 77s wp-pv-claim Bound pvc-8cd0df54-4044-11e9-b2bb-42010a800002 20Gi RWO standard 77s 

3. Verify that the Pod is running by running the following command:

   kubectl get pods 

   Note: It can take up to a few minutes for the Pod's Status to be RUNNING.

   The response should be like this:

   NAME READY STATUS RESTARTS AGE wordpress-mysql-1894417608-x5dzt 1/1 Running 0 40s 

4. Verify that the Service is running by running the following command:

   kubectl get services wordpress 

   The response should be like this:

   NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE wordpress LoadBalancer 10.0.0.89 <pending> 80:32406/TCP 4m 

   Note: Minikube can only expose Services through NodePort. The EXTERNAL-IP is always pending.

5. Run the following command to get the IP Address for the WordPress Service:

   minikube service wordpress --url 

   The response should be like this:

   http://1.2.3.4:32406 

6. Copy the IP address, and load the page in your browser to view your site.

   You should see the WordPress set up page similar to the following screenshot.

   

   Warning: Do not leave your WordPress installation on this page. If another user finds it, they can set up a website on your instance and use it to serve malicious content.
   
   Either install WordPress by creating a username and password or delete your instance.

Cleaning up

1. Run the following command to delete your Secret, Deployments, Services and PersistentVolumeClaims:

   kubectl delete -k ./ 

What's next

• Learn more about Introspection and Debugging
• Learn more about Jobs
• Learn more about Port Forwarding
• Learn how to Get a Shell to a Container