Hello Kubernetes!

This image can be deployed on a Kubernetes cluster. It displays:

• a default Hello world! message
• the pod name
• node os information

The default "Hello world!" message displayed can be overridden using the MESSAGE environment variable.

The default port of 8080 can be overriden using the PORT environment variable.

DockerHub

It is available on DockerHub as:

• paulbouwer/hello-kubernetes:1.5

Deploy

You can deploy the image to your Kubernetes cluster one of two ways:

Deploy using the hello-kubernetes.yaml, which contains definitions for the service and deployment objects:

# hello-kubernetes.yaml

apiVersion: v1
kind: Service
metadata:
  name: hello-kubernetes
spec:
  type: LoadBalancer
  ports:
  - port: 80
    targetPort: 8080
  selector:
    app: hello-kubernetes
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-kubernetes
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-kubernetes
  template:
    metadata:
      labels:
        app: hello-kubernetes
    spec:
      containers:
      - name: hello-kubernetes
        image: paulbouwer/hello-kubernetes:1.5
        ports:
        - containerPort: 8080

$ kubectl apply -f yaml/hello-kubernetes.yaml

Or, deploy by executing the following run and expose commands on kubectl.

$ kubectl run hello-kubernetes --replicas=3 --image=paulbouwer/hello-kubernetes:1.5 --port=8080
$ kubectl expose deployment hello-kubernetes --type=LoadBalancer --port=80 --target-port=8080 --name=hello-kubernetes

This will display a Hello world! message when you hit the service endpoint in a browser. You can get the service endpoint ip address by executing the following command and grabbing the returned external ip address value:

$ kubectl get service hello-kubernetes

Custom Message

You can customise the message displayed by the hello-kubernetes container as follows:

Deploy using the hello-kubernetes.custom-message.yaml, which contains definitions for the service and deployment objects:

In the definition for the deployment, add an env variable with the name of MESSAGE. The value you provide will be displayed as the custom message.

# hello-kubernetes.custom-message.yaml

apiVersion: v1
kind: Service
metadata:
  name: hello-kubernetes-custom
spec:
  type: LoadBalancer
  ports:
  - port: 80
    targetPort: 8080
  selector:
    app: hello-kubernetes-custom
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-kubernetes-custom
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-kubernetes-custom
  template:
    metadata:
      labels:
        app: hello-kubernetes-custom
    spec:
      containers:
      - name: hello-kubernetes
        image: paulbouwer/hello-kubernetes:1.5
        ports:
        - containerPort: 8080
        env:
        - name: MESSAGE
          value: I just deployed this on Kubernetes!

$ kubectl apply -f yaml/hello-kubernetes.custom-message.yaml

Or, deploy by executing the following run and expose commands on kubectl, with the environment variable MESSAGE provided as part of the run command.

$ kubectl run hello-kubernetes --replicas=3 --image=paulbouwer/hello-kubernetes:1.5 --port=8080 --env="MESSAGE=I just deployed this on Kubernetes!"
$ kubectl expose deployment hello-kubernetes --type=LoadBalancer --port=80 --target-port=8080 --name=hello-kubernetes

Custom Port

By default, the hello-kubernetes app listens on port 8080. If you have a requirement for the app to listen on another port, you can specify the port via an env variable with the name of PORT. Remember to also update the containers.ports.containerPort value to match.

Here is an example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-kubernetes-custom
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-kubernetes-custom
  template:
    metadata:
      labels:
        app: hello-kubernetes-custom
    spec:
      containers:
      - name: hello-kubernetes
        image: paulbouwer/hello-kubernetes:1.5
        ports:
        - containerPort: 80
        env:
        - name: PORT
          value: "80"

Build

If you'd like to build the image yourself, then you can do so as follows. The build-arg parameters provides metadata as defined in OCI image spec annotations.

Bash

$ docker build --no-cache --build-arg IMAGE_VERSION="1.5" --build-arg IMAGE_CREATE_DATE="`date -u +"%Y-%m-%dT%H:%M:%SZ"`" --build-arg IMAGE_SOURCE_REVISION="`git rev-parse HEAD`" -f Dockerfile -t "hello-kubernetes:1.5" .

Powershell

PS> docker build --no-cache --build-arg IMAGE_VERSION="1.5" --build-arg IMAGE_CREATE_DATE="$(Get-Date((Get-Date).ToUniversalTime()) -UFormat '%Y-%m-%dT%H:%M:%SZ')" --build-arg IMAGE_SOURCE_REVISION="$(git rev-parse HEAD)" -f Dockerfile -t "hello-kubernetes:1.5" .