Guided Exercise: Provision Persistent Data Volumes

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6 min read

Deploy a MySQL database with persistent storage from a PVC and identify the PV and storage provisioner that backs the application.

Outcomes

You should be able to do the following tasks:

  • Deploy a MySQL database with persistent storage from a PVC.

  • Identify the PV that backs the application.

  • Identify the storage provisioner that created the PV.

As the student user on the workstation machine, use the lab command to prepare your system for this exercise.

This command ensures that all resources are available for this exercise.

[student@workstation ~]$ lab start storage-volumes

Procedure 5.2. Instructions

  1. Log in to the OpenShift cluster as the developer user with the developer password. Use the storage-volumes project.

    1. Log in to the OpenShift cluster.

       [student@workstation ~]$ oc login -u developer -p developer \
         https://api.ocp4.example.com:6443
       Login successful.
       ...output omitted...
      
    2. Set the storage-volumes project as the active project.

       [student@workstation ~]$ oc project storage-volumes
       ...output omitted...
      
  2. Identify the default storage class for the cluster.

    1. Use the oc get storageclass command to identify the default storage class.

       [student@workstation ~]$ oc get storageclass
       NAME                    PROVISIONER                                   ...
       nfs-storage (default)   k8s-sigs.io/nfs-subdir-external-provisioner   ...
       lvms-vg1                topolvm.io                                    ...
      
  3. Use the registry.ocp4.example.com:8443/rhel8/mysql-80 container image to create a MySQL deployment named db-pod. Add the missing environment variables for the pod to run.

    1. Create the db-pod deployment. Ignore the warning message.

       [student@workstation ~]$ oc create deployment db-pod --port 3306 \
         --image=registry.ocp4.example.com:8443/rhel8/mysql-80
       ...output omitted...
       deployment.apps/db-pod created
      
    2. Add the environment variables. Ignore the warning message.

       [student@workstation ~]$ oc set env deployment/db-pod \
         MYSQL_USER=user1 \
         MYSQL_PASSWORD=mypa55w0rd \
         MYSQL_DATABASE=items
       ...output omitted...
       deployment.apps/db-pod updated
      
    3. Confirm that the pod is running.

       [student@workstation ~]$ oc get pods
       NAME                      READY   STATUS    RESTARTS   AGE
       db-pod-6ccc485cfc-vrc4r   1/1     Running   0          2m30s
      
    4. Expose the db-pod deployment to create a service.

       [student@workstation ~]$ oc expose deployment/db-pod
       service/db-pod exposed
      
  4. Use the oc get deployment command to view the pod template specification for the deployment.

    1. Retrieve the pod template specification for the deployment.

       [student@workstation ~]$ oc get deployment/db-pod -o json | \
         jq .spec.template.spec.containers
       [
         {
           "env": [
             {
               "name": "MYSQL_USER",
               "value": "user1"
             },
             {
               "name": "MYSQL_PASSWORD",
               "value": "mypa55w0rd"
             },
             {
               "name": "MYSQL_DATABASE",
               "value": "items"
             }
           ],
           "image": "registry.ocp4.example.com:8443/rhel8/mysql-80",
           "imagePullPolicy": "Always",
           "name": "mysql-80",
           "ports": [
             {
               "containerPort": 3306,
               "protocol": "TCP"
             }
           ],
           "resources": {},
           "terminationMessagePath": "/dev/termination-log",
           "terminationMessagePolicy": "File"
         }
       ]
      
  5. Add a 1 Gi, RWO PVC named db-pod-pvc to the deployment. Specify the volume name as nfs-volume-storage, and set the /var/lib/mysql directory as the mount path.

    1. Use the oc set volume command to create a PVC for the deployment. Ignore the warning message.

       [student@workstation ~]$ oc set volumes deployment/db-pod \
         --add --name nfs-volume-storage --type pvc \
         --claim-mode rwo --claim-size 1Gi --mount-path /var/lib/mysql \
         --claim-name db-pod-pvc
       ...output omitted...
       deployment.apps/db-pod volume updated
      
    2. Use the oc get pvc command to view the status of the PVC. Identify the name of the PV, and confirm that the PVC uses the nfs-storage default storage class.

       [student@workstation ~]$ oc get pvc
       NAME         STATUS   VOLUME          CAPACITY   ACCESS MODES   STORAGECLASS   ...
       db-pod-pvc   Bound    pvc-13...ca45   1Gi        RWO            nfs-storage    ...
      
  6. Observe how the oc set volume command changed the deployment.

    1. Use the oc get deployment command to view the deployment again.

       [student@workstation ~]$ oc get deployment/db-pod -o yaml
       apiVersion: apps/v1
       kind: Deployment
      
       ...output omitted...
      
               volumeMounts:
               - mountPath: /var/lib/mysql
                 name: nfs-volume-storage
      
       ...output omitted...
      
             volumes:
             - name: nfs-volume-storage
               persistentVolumeClaim:
                 claimName: db-pod-pvc
      
       ...output omitted...
      
  7. Use a configMap resource as a temporary volume to add initialization data to the database.

    1. Observe the contents of the init-db.sql script that initializes the database.

       [student@workstation ~]$ cat \
         ~/DO180/labs/storage-volumes/configmap/init-db.sql
      
        DROP TABLE IF EXISTS `Item`;
        CREATE TABLE `Item` (`id` BIGINT not null auto_increment primary key, `description` VARCHAR(100), `done` BIT);
        INSERT INTO `Item` (`id`,`description`,`done`) VALUES (1,'Pick up newspaper', 0);
        INSERT INTO `Item` (`id`,`description`,`done`) VALUES (2,'Buy groceries', 1);
      
    2. Use the contents of the init-db.sql file to create a configMap API object named init-db-cm.

       [student@workstation ~]$ oc create configmap init-db-cm \
         --from-file=/home/student/DO180/labs/storage-volumes/configmap/init-db.sql
       configmap/init-db-cm created
      
    3. Add the init-db-cm configMap resource as a volume named init-db-volume to the deployment. Specify the volume type as configmap, and set the /tmp/init-db directory as the mount path. Ignore the warning message.

       [student@workstation ~]$ oc set volumes deployment/db-pod \
         --add --name init-db-volume \
         --configmap-name init-db-cm --type configmap \
         --mount-path /tmp/init-db
       ...output omitted...
       deployment.apps/db-pod volume updated
      
    4. Capture the name of the pod in a variable.

       [student@workstation ~]$ PODNAME=$(oc get pods \
         -o jsonpath='{.items[0].metadata.name}')
      
    5. Start a remote shell session inside the container.

       [student@workstation ~]$ oc rsh $PODNAME
       sh-4.4$
      
    6. Use the mysql client to execute the database script in the /tmp/init-db volume.

       sh-4.4$ mysql -uuser1 -pmypa55w0rd items </tmp/init-db/init-db.sql
       mysql: [Warning] Using a password on the command line interface can be insecure.
       sh-4.4$
      
    7. Exit the shell session.

       sh-4.4$ exit
      
    8. Use the oc set volume command to remove the init-db-volume volume from the dp-pod deployment. Ignore the warning message.

       [student@workstation ~]$ oc set volumes deployment/db-pod \
         --remove --name init-db-volume
       ...output omitted...
       deployment.apps/db-pod volume updated
      
  8. Create a query-db pod by using the oc run command and the registry.ocp4.example.com:8443/redhattraining/do180-dbinit container image. Use the pod to execute a query against the database service.

    1. Create the query-db pod. Configure the pod to use the MySQL client to execute a query against the db-pod service. Ignore the warning message.

       [student@workstation ~]$ oc run query-db -it --rm \
         --image registry.ocp4.example.com:8443/redhattraining/do180-dbinit \
         --restart Never --command \
         -- /bin/bash -c "mysql -uuser1 -pmypa55w0rd --protocol tcp \
         -h db-pod -P3306 items -e 'select * from Item;'"
       mysql: [Warning] Using a password on the command line interface can be insecure.
       +----+-------------------+------------+
       | id | description       | done       |
       +----+-------------------+------------+
       |  1 | Pick up newspaper | 0x00       |
       |  2 | Buy groceries     | 0x01       |
       +----+-------------------+------------+
       pod "query-db" deleted
      
  9. Delete and then re-create the db-pod deployment.

    1. Delete the db-pod deployment.

       [student@workstation ~]$ oc delete deployment/db-pod
       deployment.apps "db-pod" deleted
      
    2. Verify that the PVC still exists without the deployment.

       [student@workstation ~]$ oc get pvc
       NAME         STATUS   VOLUME                                     CAPACITY   ...
       db-pod-pvc   Bound    pvc-ab5b38c7-359a-4e99-b81c-f7d11ef91cc9   1Gi        ...
      
    3. Re-create the db-pod deployment. Ignore the warning message.

       [student@workstation ~]$ oc create deployment db-pod --port 3306 \
         --image=registry.ocp4.example.com:8443/rhel8/mysql-80
       ...output omitted...
       deployment.apps/db-pod created
      
    4. Add the environment variables. Ignore the warning message.

       [student@workstation ~]$ oc set env deployment/db-pod \
         MYSQL_USER=user1 \
         MYSQL_PASSWORD=mypa55w0rd \
         MYSQL_DATABASE=items
       ...output omitted...
       deployment.apps/db-pod updated
      
  10. Use the oc set volume command to attach the existing PVC to the deployment. Ignore the warning message.

    [student@workstation ~]$ oc set volumes deployment/db-pod \
      --add --type pvc \
      --mount-path /var/lib/mysql \
      --claim-name db-pod-pvc
    info: Generated volume name: volume-kfl28
    ...output omitted...
    deployment.apps/db-pod volume updated
    
  11. Create a query-db pod by using the oc run command and the registry.ocp4.example.com:8443/redhattraining/do180-dbinit container image. Use the pod to execute a query against the database service.

    1. Create the query-db pod. Configure the pod to use the MySQL client to execute a query against the db-pod service. Ignore the warning message.

       [student@workstation ~]$ oc run query-db -it --rm \
         --image registry.ocp4.example.com:8443/redhattraining/do180-dbinit \
         --restart Never --command \
         -- /bin/bash -c "mysql -uuser1 -pmypa55w0rd --protocol tcp \
         -h db-pod -P3306 items -e 'select * from Item;'"
       mysql: [Warning] Using a password on the command line interface can be insecure.
       +----+-------------------+------------+
       | id | description       | done       |
       +----+-------------------+------------+
       |  1 | Pick up newspaper | 0x00       |
       |  2 | Buy groceries     | 0x01       |
       +----+-------------------+------------+
       pod "query-db" deleted
      
  12. Delete the db-pod deployment and the db-pod-pvc PVC.

    1. Delete the db-pod deployment.

       [student@workstation ~]$ oc delete deployment/db-pod
       deployment.apps "db-pod" deleted
      
    2. Delete the db-pod-pvc PVC.

       [student@workstation ~]$ oc delete pvc/db-pod-pvc
       persistentvolumeclaim "db-pod-pvc" deleted
      

Finish

On the workstation machine, use the lab command to complete this exercise. This step is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish storage-volumes