README.md

More on Storage

• Kubernetes Storage documentation.

PersistentVolume

• Kubernetes.io Persistent Volumes
• Minikube Persistent Volumes
• Create a PersistentVolume

Apply pvol000-pv.yaml:

kubectl apply -f pvol000-pv.yaml
kubectl describe persistentvolume/pvol000

PersistentVolumeClaim

• PersistentVolumeClaims
• Create a PersistentVolumeClaim

Apply pvol000-pv-claim.yaml:

kubectl apply -f pvol000-pv-claim.yaml
kubectl describe persistentvolumeclaim/pvol000-pv-claim

Using a PersistentVolumeClaim

• Claims As Volumes

Apply postgres-deployment.yaml:

kubectl apply -f postgres-deployment.yaml
kubectl get pvc,pv,pods,svc,deployment
kubectl describe deployment.apps/postgres
kubectl describe service/postgres
minikube service list

Explore:

• Using a SQL client like DBeaver, connect to the database using the password "Use-a-Better-Passw0rd" along with the IP address and port number from the service list above:

• Verify this query select * from products; fails with a products table does not exist error.

• Run this script in a new SQL Editor:

  drop table if exists products;
  
  CREATE TABLE products (
      product_no integer,
      name text,
      price numeric
  );
  
  INSERT INTO products (product_no, name, price) VALUES
      (1, 'Cheese', 9.99),
      (2, 'Bread', 1.99),
      (3, 'Milk', 2.99);
  

• Verify the table has data: select * from products;

• Disconnect from the database

• Scale down to zero to kill the pod:

  kubectl scale deployment.apps/postgres --replicas=0
  kubectl get all --show-labels
  

• Scale back to 1 instance:

  kubectl scale deployment.apps/postgres --replicas=1
  kubectl get all --show-labels
  

• In DBeaver, reconnect to the database

• Verify the table still exists and has data: select * from products;

• Quit DBeaver

Clean up

kubectl get pvc,pv,pods,svc,deployment
kubectl delete deployment.apps/postgres service/postgres
kubectl get pvc,pv,pods,svc,deployment
kubectl delete persistentvolumeclaim/pvol000-pv-claim
kubectl get pvc,pv,pods,svc,deployment
kubectl delete persistentvolume/pvol000

Passing configuration as file data

Using ephemeral volumes

Mount various configuration data using different volumes into multiple directories

References:

• Ephemeral Volumes
• ConfigMaps
• Secrets
• Expose Pod Information to Containers Through Files

Apply ephemeral-vol-test-pod.yaml:

kubectl apply -f ephemeral-vol-test-pod.yaml
kubectl get all,cm,secrets

Explore:

• Shell in and look around with kubectl exec -it ephemeral-vol-test -- /bin/sh or run the commands below:

  kubectl exec -it ephemeral-vol-test -- ls -lR /configuration/
  
  kubectl exec -it ephemeral-vol-test -- find /configuration/ -type f -exec echo "contents of" {} ":" \; -exec cat {} \; -exec echo "" \;
  

• Clean up:

  kubectl get all,cm,secrets
  
  kubectl delete pod/ephemeral-vol-test
  kubectl delete secret db-secrets
  kubectl delete configmap/config-map-demo
  

Using Projected volumes

Mount various configuration data using projected volumes into a common directory

References:

• Projected Volumes

Apply projected-vol-test-pod.yaml:

kubectl apply -f projected-vol-test-pod.yaml

Explore:

• Shell in and look around with kubectl exec -it projected-vol-test -- /bin/sh or run the commands below.

  kubectl exec -it projected-vol-test -- ls -lR /configuration/
  kubectl exec -it projected-vol-test -- ls -lR /configuration/..data/
  

• Print the file name and contents of all configuration data:

  kubectl exec -it projected-vol-test -- find /configuration/ -type f -exec echo "contents of" {} ":" \; -exec cat {} \; -exec echo "" \;
  

• Examine only the secrets:

  kubectl exec -it projected-vol-test -- cat /configuration/db/password; echo ""
  kubectl exec -it projected-vol-test -- cat /configuration/db/username; echo ""
  

• Examine only the config from downwardAPI:

  kubectl exec -it projected-vol-test -- cat /configuration/cpu_limit; echo ""
  kubectl exec -it projected-vol-test -- cat /configuration/..data/labels; echo ""
  

• Examine only the config from the ConfigMap:

  kubectl exec -it projected-vol-test -- cat /configuration/..data/home_track; echo ""
  kubectl exec -it projected-vol-test -- cat /configuration/..data/meaning_of_life; echo ""
  kubectl exec -it projected-vol-test -- cat /configuration/..data/race.properties
  

• Clean up:

  kubectl get all,cm,secrets
  
  kubectl delete pod projected-vol-test
  kubectl delete secret db-secrets
  kubectl delete configmap/config-map-demo
  

Passing configuration as environment variables

References:

• Expose Pod Information to Containers Through Environment Variables

Apply env-vars-test-pod.yaml:

kubectl apply -f env-vars-test-pod.yaml
kubectl get all,pvc,cm,secrets

Explore:

• Shell in and look around with kubectl exec -it environment-vol-test -- /bin/sh or run the commands below.

  kubectl exec -it environment-vol-test -- printenv
  

• Clean up:

  kubectl delete secret/db-secrets configmap/config-map-demo pod/environment-vol-test
  kubectl get all,pvc,cm,secrets