test #3

Simple start to finish of turning a python script into a container to run in kubernetes

Docker Hub: https://hub.docker.com/u/aschiebold

Here's a simple Python script to calculate 1+1 and print the result: python

Calculate 1+1

result = 1 + 1

Print the result

print("1 + 1 =", result)

When you run this script, it will output:

1 + 1 = 2

This script:

Performs the addition of 1+1 and stores it in the variable result
Uses the print() function to display the calculation and its result

Here's a Dockerfile that will containerize the Python script to calculate 1+1: dockerfile

Use official Python runtime as base image

FROM python:3.9-slim

Set working directory in container

WORKDIR /app

Copy the Python script to container

COPY script.py .

Run the script when container launches

CMD ["python", "script.py"]

To use this Dockerfile:

Save the Python script from my previous response as script.py
Save this Dockerfile as Dockerfile (no extension) in the same directory
Build the Docker image:

bash

docker build -t calculator .

Run the container:

bash

docker run calculator

This Dockerfile:

Uses Python 3.9 slim version as the base image (lightweight Python environment)
Sets the working directory to /app in the container
Copies the script.py file into the container
Sets the command to run the Python script when the container starts

When you run the container, it will execute the script and output "1 + 1 = 2" to the console, then exit. Note: Make sure both files are in the same directory when building the Docker image.

Here's a step-by-step guide to push your Docker image to Docker Hub: Prerequisites

You have Docker installed and running
You have a Docker Hub account (if not, create one at hub.docker.com)
You've built the image locally using the previous Dockerfile

Steps to Push to Docker Hub

Login to Docker Hub from your terminal

bash

docker login

Enter your Docker Hub username and password when prompted
If successful, you'll see "Login Succeeded"

Tag your image
Your image needs to be tagged with your Docker Hub username/repository format. Replace your-username with your actual Docker Hub username:

bash

docker tag calculator your-username/calculator:latest

calculator is the local image name from our previous build
your-username/calculator will be the repository name on Docker Hub
:latest is the tag (you can use other tags like :v1.0 if you prefer)

Push the image to Docker Hub

bash

docker push your-username/calculator:latest

This uploads your image to your Docker Hub repository
You'll see the upload progress for each layer

Full Example Assuming your Docker Hub username is "johndoe" and you built the image as "calculator": bash

Login

docker login

Tag the image

docker tag calculator johndoe/calculator:latest

Push to Docker Hub

docker push johndoe/calculator:latest

Verification

After pushing, visit hub.docker.com/u/your-username in your browser
You should see your "calculator" repository
The repository will be public by default (unless you have a paid plan for private repos)

Notes

If the repository doesn't exist yet, Docker Hub will create it automatically when you push
If you get a "denied: requested access to the resource is denied" error:
    Double-check your username
    Ensure you're logged in (try docker login again)
To make the repository private, log into Docker Hub website and adjust the settings after pushing

Now anyone can pull and run your image with: bash

docker pull your-username/calculator:latest docker run your-username/calculator:latest

To run your Docker container in Kubernetes, you'll need to create a Kubernetes deployment and apply it to a cluster. Here's a step-by-step guide: Prerequisites

You have a Kubernetes cluster running (e.g., Minikube locally or a cloud provider like GKE, EKS, AKS)
kubectl is installed and configured to communicate with your cluster
You've pushed your image to Docker Hub (e.g., your-username/calculator:latest)

Steps to Run in Kubernetes

Create a Kubernetes Deployment YAML file
Create a file named calculator-deployment.yaml with this content (replace your-username with your Docker Hub username):

yaml

apiVersion: apps/v1 kind: Deployment metadata: name: calculator-deployment labels: app: calculator spec: replicas: 1 selector: matchLabels: app: calculator template: metadata: labels: app: calculator spec: containers: - name: calculator image: your-username/calculator:latest imagePullPolicy: IfNotPresent

This YAML:

Defines a Deployment named calculator-deployment
Runs 1 replica (pod)
Uses your Docker Hub image
Labels the app as "calculator" for identification

Apply the Deployment to your cluster
Run this command in the directory containing your YAML file:

bash

kubectl apply -f calculator-deployment.yaml

This creates the deployment in your Kubernetes cluster

Verify the Deployment
Check that the deployment is running:

bash

kubectl get deployments

You should see something like:

NAME READY UP-TO-DATE AVAILABLE AGE calculator-deployment 1/1 1 1 10s

Check the pods: bash

kubectl get pods

You should see a pod with a name like calculator-deployment-xyz123-abcde

View the Output
Since this is a simple script that runs once and exits, the pod will complete and enter a "Completed" state. To see the output:

bash

kubectl logs

Replace with the actual pod name from kubectl get pods. You should see:

1 + 1 = 2

Notes

Job vs Deployment: Since your container runs once and exits, a Kubernetes Job might be more appropriate than a Deployment. Here's an alternative calculator-job.yaml:

yaml

apiVersion: batch/v1 kind: Job metadata: name: calculator-job spec: template: spec: containers: - name: calculator image: your-username/calculator:latest restartPolicy: Never

Apply it with: bash

kubectl apply -f calculator-job.yaml

Local Testing with Minikube:
    Start Minikube: minikube start
    Apply the deployment/job
    When done, clean up with kubectl delete -f calculator-deployment.yaml and minikube stop
Cleanup:
    Delete the deployment: kubectl delete deployment calculator-deployment
    Delete the job: kubectl delete job calculator-job
Troubleshooting:
    If the pod fails, use kubectl describe pod <pod-name> to see details
    Ensure your cluster can pull from Docker Hub (public images don't need credentials)

This will run your simple calculator container in Kubernetes! For a more persistent application, you'd typically add a Service and possibly an Ingress, but for this one-time calculation, a Job or simple Deployment is sufficient.