Learning Kubernetes (with minikube)

learning-k8s-with-minikube.md

Learning Kubernetes

I'm running this on Mac OSX 10+!

Pre-req:

• VirtualBox (there are other alternatives)
• kubectl
• minikube
• jq

Install everything:

1. Download and install VirtualBox
2. Install kubectl

curl -LO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/darwin/amd64/kubectl && chmod +x kubectl && mv ./kubectl /usr/local/bin/

3. Install minikube (latest version as of writing this)

curl -Lo minikube https://storage.googleapis.com/minikube/releases/v0.24.1/minikube-darwin-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/

4. Install jq via brew

Optional

1. Start the Kubernetes dashboard, minikube will start a new browser session to the dashboard!

minikube dashboard

Excersise 1 - Getting started

1. Create a namespace

kubectl create namespace mikejoh

2. Run a image on the cluster, in this case David C's hello-world image. Starts three pods via the replica option

kubectl run dotnet --image=sharor/hello-world --replicas=3 -n mikejoh

3. Describe all of the pods (three in this case)

kubectl describe pod $(kubectl get pods -n mikejoh -o json | jq '.items[].metadata.name' --raw-output) -n mikejoh

4. Check the pods

kubectl get pods -n mikejoh

5. Expose a replication controller, service or pod as a new Kubernetes Service

kubectl expose deployment dotnet --type=NodePort --port=5000 -n mikejoh

6. Check the service

$ kubectl describe svc dotnet -n mikejoh
Name:                     dotnet
Namespace:                mikejoh
Labels:                   run=dotnet
Annotations:              <none>
Selector:                 run=dotnet
Type:                     NodePort
IP:                       10.103.61.43
Port:                     <unset>  5000/TCP
TargetPort:               5000/TCP
NodePort:                 <unset>  32099/TCP
Endpoints:                172.17.0.4:5000,172.17.0.5:5000,172.17.0.6:5000
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

7. Now try to reach the exposed service via the NodePort outputted above (port 32099 in this case).

curl -I http://192.168.99.100:32099
HTTP/1.1 200 OK
Date: Wed, 03 Jan 2018 16:03:55 GMT
Transfer-Encoding: chunked
Content-Type: text/html; charset=utf-8
Server: Kestrel

8. If you delete your namespace you can extract the deployment as yaml and use it later on

kubectl get deployment dotnet -o yaml -n mikejoh > myapp-deployment.yml

9. To target your own namespace instead of the default one each time you run a command (without the -n flag), you can run this

kubectl config set-context $(kubectl config current-context) --namespace=mikejoh

Excercise 2 - Secrets and ConfigMaps

The flow of this excercise:

• An app that reads two environment variables, API_KEY and LANGUAGE, and outputs these when you browse to the container

1. Dockerfile with ENV

...
ENV LANGUAGE English
ENV API_KEY 123-456-789
...

2. These gets overridden by the env in the k8s deployment yml-file. We have now hardcoded the secrets in our deployment yml-file, that's not what we want, deployment files will also be shared in various ways.

...
env:
  - name: LANGUAGE
    value: Polish
  - name: API_KEY
    value: 333-444-555
...

3. We'll create a secret and a ConfigMap within our k8s cluster and namespace
4. We'll swap out the env values once more from CLI
5. Since the pods have a cache, we need to delete the pod so that it'll be recreated and using the new values

The commands

1. Apply a deployment

kubectl apply -f deployment.yml 

2. Create a generic secret

kubectl create secret generic apikey --from-literal=API_KEY=oneringtorulethemall

3. Create a ConfigMap

kubectl create configmap language --from-literal=LANGUAGE=Orcish

4. Change the deployment yml-file to reference the secrets and ConfigMaps

    env:
        - name: LANGUAGE
          valueFrom:
            configMapKeyRef:
              name: language
              key: LANGUAGE
        - name: API_KEY
          valueFrom:
            secretKeyRef:
              name: apikey
              key: API_KEY