Create a Dockerfile(SCA-cloud internship test).

A few weeks ago, She Code Africa called for applications for its cloud internship. 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.
• Nodejs Command line tool installed.

Step 1: Create a GitHub repository

• Create a 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 ( 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”
}

Project Structure

Project Structure

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

index.html
The index.html file is in the views folder.

• 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 4990:8080 -d dockerdemo

• Go to your docker desktop to view and run the docker image.

• Your docker image should be running on http://localhost:49160
  To view 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 image-id yourhubusername/reponame:tag
  Example: docker tag 9c9f09c6e82e yourhubusername/sca-cloud-docker:stable
• Run docker push yourhubusername/reponame:tag
  Example: docker push yourhubusername/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-feature n/b: we use a different port number
• Run your generated image on the docker desktop, confirm at http://localhost:4990
• Add, commit and push the feature branch to GitHub.
• Push to the same docker repository docker tag image-id:yourhubusername/reponame:tag , docker push yourhubusername/reponame:tag n/b: we use the feature as a tag.

Other things to note 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.

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!