Docker Hub as image registry - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Docker login command output

What is the expected output after successfully logging into Docker Hub using the command docker login?

Docker

docker login

A Cannot connect to the Docker daemon

B Error: unauthorized: incorrect username or password

C Login Succeeded

D Usage: docker login [OPTIONS] SERVER

💡 Hint

Think about what message confirms a successful login.

When you run 'docker login' and provide correct credentials, Docker Hub responds with 'Login Succeeded'. Other messages indicate errors or incorrect usage.

🧠 Conceptual

intermediate

Purpose of Docker Hub repository tags

Why do we use tags in Docker Hub repositories?

A To identify different versions or variants of the same image

B To encrypt the Docker images for security

C To limit the number of downloads per image

D To automatically update the image on all servers

💡 Hint

Think about how you keep track of different versions of a file.

Tags help label images with versions or variants, making it easy to pull the exact image you want. They do not encrypt, limit downloads, or auto-update images.

🔀 Workflow

advanced

Correct sequence to push a Docker image to Docker Hub

Arrange the steps in the correct order to push a Docker image named myapp with tag v1 to Docker Hub.

A 3,4,1,2

B 4,3,1,2

C 4,1,3,2

D 3,1,4,2

💡 Hint

You must login before pushing, and tagging happens after building.

First, login to Docker Hub (4). Then build the image locally (3). Next, tag the image with your Docker Hub username (1). Finally, push the tagged image to Docker Hub (2).

❓ Troubleshoot

advanced

Error when pushing image: denied: requested access to the resource is denied

You get the error denied: requested access to the resource is denied when running docker push username/myapp:v1. What is the most likely cause?

A Your internet connection is down

B The Docker daemon is not running on your machine

C The image name contains invalid characters

D You are not logged in or logged in with a different Docker Hub account

💡 Hint

Think about permissions and authentication with Docker Hub.

This error usually means you are not authenticated properly or trying to push to a repository you don't have permission for. Other options cause different errors.

✅ Best Practice

expert

Recommended practice for managing sensitive data in Docker images pushed to Docker Hub

Which practice is best to avoid exposing sensitive data when pushing Docker images to Docker Hub?

A Use multi-stage builds to exclude secrets from the final image

B Include secrets in environment variables inside the Dockerfile

C Push images with all configuration files including passwords

D Store secrets in plain text files inside the image

💡 Hint

Think about how to keep secrets out of the final image.

Multi-stage builds allow you to copy only necessary artifacts into the final image, leaving secrets out. Including secrets in Dockerfiles or images risks exposure.