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Detailed walkthroughs of common Kubernetes operations and workflows.

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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 provisioned by an administrator, and a PersistentVolumeClaim (PVC) is a set amount of storage in a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods.

Warning: This deployment is not suitable for production use cases, as it uses single instance WordPress and MySQL Pods. Consider using WordPress Helm Chart to deploy WordPress in production.

Note: The files provided in this tutorial are using beta Deployment APIs and are specific to kubernetes version 1.8. If you wish to use this tutorial with an earlier version of Kubernetes, please update the beta API appropriately, or reference earlier versions of this tutorial.

Objectives

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.

Download the following configuration files:

  1. local-volumes.yaml

  2. mysql-deployment.yaml

  3. wordpress-deployment.yaml

Create a PersistentVolume

MySQL and Wordpress each use a PersistentVolume to store data. While Kubernetes supports many different types of PersistentVolumes, this tutorial covers hostPath.

Note: If you have a Kubernetes cluster running on Google Kubernetes Engine, please follow this guide.

Setting up a hostPath Volume

A hostPath mounts a file or directory from the host node’s filesystem into your Pod.

Warning: Only use hostPath for developing and testing. With hostPath, your data lives on the node the Pod is scheduled onto and does not move between nodes. If a Pod dies and gets scheduled to another node in the cluster, the data is lost.

  1. Launch a terminal window in the directory you downloaded the manifest files.

  2. Create two PersistentVolumes from the local-volumes.yaml file:

    kubectl create -f local-volumes.yaml
mysql-wordpress-persistent-volume/local-volumes.yaml 
apiVersion: v1
kind: PersistentVolume
metadata:
  name: local-pv-1
  labels:
    type: local
spec:
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /tmp/data/pv-1
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: local-pv-2
  labels:
    type: local
spec:
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /tmp/data/pv-2

  1. Run the following command to verify that two 20GiB PersistentVolumes are available:

    kubectl get pv

    The response should be like this:

    NAME         CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM     STORAGECLASS   REASON    AGE
local-pv-1   20Gi       RWO           Retain          Available                                      1m
local-pv-2   20Gi       RWO           Retain          Available                                      1m

Create a Secret for MySQL Password

A Secret is an object that stores a piece of sensitive data like a password or key. The manifest files are already configured to use a Secret, but you have to create your own Secret.

  1. Create the Secret object from the following command:

    kubectl create secret generic mysql-pass --from-literal=password=YOUR_PASSWORD

    Note: Replace YOUR_PASSWORD with the password you want to apply.

  2. 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                 Opaque                                1         42s

    Note: To protect the Secret from exposure, neither get nor describe show its contents.

Deploy MySQL

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.

mysql-wordpress-persistent-volume/mysql-deployment.yaml 
apiVersion: v1
kind: Service
metadata:
  name: wordpress-mysql
  labels:
    app: wordpress
spec:
  ports:
    - port: 3306
  selector:
    app: wordpress
    tier: mysql
  clusterIP: None
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
  labels:
    app: wordpress
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1beta2 # for versions before 1.8.0 use apps/v1beta1
kind: Deployment
metadata:
  name: wordpress-mysql
  labels:
    app: wordpress
spec:
  selector:
    matchLabels:
      app: wordpress
      tier: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: wordpress
        tier: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-pass
              key: password
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

  1. Deploy MySQL from the mysql-deployment.yaml file:

    kubectl create -f mysql-deployment.yaml

  2. 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

Deploy WordPress

The following manifest describes a single-instance WordPress Deployment and Service. It uses many of the same features like a PVC for persistent storage and a Secret for the password. But it also uses a different setting: type: NodePort. This setting exposes WordPress to traffic from outside of the cluster.

mysql-wordpress-persistent-volume/wordpress-deployment.yaml 
apiVersion: v1
kind: Service
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  ports:
    - port: 80
  selector:
    app: wordpress
    tier: frontend
  type: LoadBalancer
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: wp-pv-claim
  labels:
    app: wordpress
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1beta2 # for versions before 1.8.0 use apps/v1beta1
kind: Deployment
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  selector:
    matchLabels:
      app: wordpress
      tier: frontend
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: wordpress
        tier: frontend
    spec:
      containers:
      - image: wordpress:4.8-apache
        name: wordpress
        env:
        - name: WORDPRESS_DB_HOST
          value: wordpress-mysql
        - name: WORDPRESS_DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-pass
              key: password
        ports:
        - containerPort: 80
          name: wordpress
        volumeMounts:
        - name: wordpress-persistent-storage
          mountPath: /var/www/html
      volumes:
      - name: wordpress-persistent-storage
        persistentVolumeClaim:
          claimName: wp-pv-claim

  1. Create a WordPress Service and Deployment from the wordpress-deployment.yaml file:

    kubectl create -f wordpress-deployment.yaml

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

    kubectl get services wordpress

    The response should be like this:

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

    Note: Minikube can only expose Services through NodePort.

    The EXTERNAL-IP is always <pending>.

  3. 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

  4. 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.

    wordpress-init

    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:

    kubectl delete secret mysql-pass

  2. Run the following commands to delete all Deployments and Services:

    kubectl delete deployment -l app=wordpress
kubectl delete service -l app=wordpress

  3. Run the following commands to delete the PersistentVolumeClaims and the PersistentVolumes:

    kubectl delete pvc -l app=wordpress
kubectl delete pv local-pv-1 local-pv-2

    Note: Any other Type of PersistentVolume would allow you to recreate the Deployments and Services at this point without losing data, but hostPath loses the data as soon as the Pod stops running.

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