Create a Dockerfile(SCA-cloud internship test).

4 min readJan 30, 2021

A few weeks ago, The She Code Africa organization called for applications for its cloud internship, and one of the technical assessments was on Docker containers. You can look up the assessment here. Was the test too challenging for you? well, it’s not too late to learn now.

Basically, the whole idea is to run an application from a Docker container. Just like running an app on localhost, but this time it’s on the Docker environment. Our preferred language is JavaScript and we will be running a Nodejs application from a docker container.

Okay, let’s start.

Prerequisites

A GitHub account http://github.com/
An account at Docker hub at docker.com
Download and set up your Docker desktop.
Stable version of Nodejs installed.

Step 1: Create a GitHub repository

Create a GitHub repository named SCA Cloud School Application on your GitHub account. Remember to add a README.md file.
Clone the repository using your terminal. You are currently on the master or main branch.

Step 2: Set up Nodejs Application.

Switch to a branch named stable — git checkout -b stable and create a folder named docker in your project folder.

Run npm init and follow the prompts ( name: docker-sample, Entry point: app.js)
Run npm install express

This is what your package.json file should look like.

Note: Replace script object

“scripts”: { 
“test”: “echo \”Error: no test specified\” && exit 1"
},

with

“scripts”: {
“start”: “node app.js”
}

Create a views folder at the root folder, and add an index.htmlfile

Project Structure

In the App.js file, set up a Nodejs server using Express.

App.js file

Add to the the index.html file in the views folder.

index.html

On the terminal , runnpm start you should have your server running on port 8080. Go the http://localhost:8080 on your browser to view the message Welcome to SCA Cloud School Application

Step 3: Set up the Dockerfile.

Add these codes to your Dockerfile

Add
node_modules
.dockerignore
.gitignore
npm-debug.log
Dockerfile
to the .dockerignore file, to prevent the files from being copied to the docker image during the build. The .dockerignore is similar to .gitignore

Step 4: Build a Docker image

Run docker build -t dockerdemo .where dockerdemo is the name of your image. Run docker run -p 49160:8080 -d dockerdemo (4990 is a random new port number, you could use any number)
Go to your docker desktop to view and run the docker image.

Your docker image should be running on http://localhost:49160
To view all images in your container, Run docker images on your terminal.

Step 5: Push to GitHub

Remember, you are on the stable branch.
Rungit add .and git commit -m "commit-message" and git push to push the docker folder to the SCA-GitHub repository.

Step 6: Push to DockerHub

Create a repository in Docker Hub named sca-cloud-docker.
Run docker tag dockerdemo <<dockerhub-username>>/sca-cloud-docker:stable
Run docker push <<dockerhub-username>>/sca-cloud-docker:stable

Step 7: Feature Branch (similar to stable branch)

Check out to feature branch git checkout -b feature
Change the content of the index.html file to “Welcome to SCA Cloud School Application, this is my first assessment”
Build and run a docker image docker build -t docker-feature ,docker run -p 4990:8080 -d docker-featureN/b: we use a different port number
Run your generated image on the docker desktop and confirm your application is working on http://localhost:4990
Add, commit and push the feature branch to GitHub.
Push to the same docker repository
docker tag docker-feature <<dockerhub-username>>/sca-cloud-docker:feature
docker push <<dockerhub-username>>/sca-cloud-docker:featureN/b: we use the feature as a tag.

Other things based on instruction:

Merge the feature branch to stable and do not delete the feature branch.
The master branch should have only a README.md file with documentation.

And that is it…✌ You can view the Repository here

I hope this really helped someone. I appreciate your comments and questions if you get stuck. BYE!