6  Week 3 (16-Oct-2025)

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6.1 Docker Introductory Exercises

6.1.1 9. Build a Docker Image from a Dockerfile

• Exercise: Create a simple Dockerfile that uses the nginx base image and copies an index.html file into the container.

• Solution:

  Create a directory for your project:

     mkdir my-nginx
     cd my-nginx

  1. Create a file named Dockerfile:

          FROM nginx
          COPY index.html /usr/share/nginx/html/index.html
          # Expose the port
          EXPOSE 80

  2. Create a simple index.html with some content in the same directory.
  3. Build the Docker image:

        docker build -t my-nginx .

• Expected Output: Successful build message with a new image tagged as my-nginx.

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6.1.2 10. Run a Container with a Volume

• Exercise: Run the nginx container and mount a host directory to the container.
• Solution:

     docker run -d -p 8080:80 -v /path/to/local/directory:/usr/share/nginx/html nginx

• Confirmation: Now put some files in directory /path/to/local/directory and check that they appear in the container in folder /usr/share/nginx/html .

• Note: Replace /path/to/local/directory with the path to your directory containing HTML files.

• Expected Output: A unique container ID indicating that the container is running.

• Verification: Open http://localhost:8080 in a web browser to see the content of the mounted directory.

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6.1.3 11. Connect to a running Container

To connect to a running container called nginx, you can use the docker exec command. This allows you to run commands inside the container and access its shell. Here’s how you can do it:

  docker exec -it nginx /bin/bash

6.1.4 Explanation:

• docker exec: This command runs a command in a running container.
• -it: This flag allows you to interact with the container (interactive mode and pseudo-TTY).
• nginx: The name or ID of the running container you want to connect to.
• /bin/bash: The shell you want to use. If your container doesn’t have bash, you can try /bin/sh instead.

After running this command, you will be inside the nginx container’s shell, where you can navigate and execute commands as needed.

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Pushing an image to Docker Hub involves a few straightforward steps. Here’s a complete example of how to do it:

6.1.5 12. Log In to Docker Hub

• Registration: Open Docker Hub Registration (https://hub.docker.com) in a web browser to register in Docker Hub.

Before you can push an image to Docker Hub, you need to log in:

docker login

You will be prompted to enter your Docker Hub username and password.

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• According with the username you created on Docker Hub, build your image with that username. (for example: if your username is jcppc).

• Build the Docker image: docker build -t jcppc/my-nginx .

        docker build -t yourusername/my-nginx .

6.1.6 13. Push the Image to Docker Hub

Now you can push your image to Docker Hub:

docker push yourusername/my-nginx:latest

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6.1.7 14. Verify the Image on Docker Hub

After a successful push, you can verify that your image has been uploaded by visiting your Docker Hub profile here and looking for yourusername/my-nginx in your repositories.

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6.1.8 Conclusion

You have successfully created a Docker image for a simple Website application, built it, and pushed it to Docker Hub. You can now share this image with others or deploy it on various platforms that support Docker.

These exercises introduce basic Docker concepts, from running containers to creating images and using volumes. Completing them will give you a solid foundation in Docker usage.