Docker Hub as image registry - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to log in to Docker Hub.

Docker

docker [1]

Drag options to blanks, or click blank then click option'

Alogin

Blogout

Cpush

Dpull

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker push' instead of 'docker login' to sign in.

Trying 'docker logout' when you want to sign in.

The docker login command lets you sign in to Docker Hub to push or pull images.

2fill in blank

medium

Complete the command to push a Docker image named 'myapp' to Docker Hub under user 'alice'.

Docker

docker push alice/[1]

Drag options to blanks, or click blank then click option'

Alatest

Bcontainer

Cimage

Dmyapp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'latest' as the image name instead of the actual image name.

Confusing container names with image names.

You push the image by specifying your Docker Hub username and the image name, like alice/myapp.

3fill in blank

hard

Fix the error in the command to tag a local image 'app' for Docker Hub user 'bob' with tag 'v1'.

Docker

docker tag app [1]/app:v1

Drag options to blanks, or click blank then click option'

Aalice

Bbob

Capp

Dv1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'alice' instead of the correct username 'bob'.

Using the tag 'v1' as the username.

The tag must include your Docker Hub username before the image name, so 'bob/app:v1' is correct.

4fill in blank

hard

Fill both blanks to pull the image 'nginx' with tag 'stable' from Docker Hub.

Docker

docker [1] nginx:[2]

Drag options to blanks, or click blank then click option'

Apull

Bpush

Cstable

Dlatest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'push' instead of 'pull' to download images.

Using 'latest' tag instead of 'stable' when specified.

The command to download an image is docker pull, and the tag specifies the version, here 'stable'.

5fill in blank

hard

Fill all three blanks to build a Docker image from 'Dockerfile' and tag it for user 'carol' with name 'webapp' and tag 'v2'.

Docker

docker build -t [1]/[2]:[3] .

Drag options to blanks, or click blank then click option'

Acarol

Bwebapp

Cv2

Dlatest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'latest' tag instead of 'v2'.

Mixing up username and image name positions.

The build command tags the image with your Docker Hub username, image name, and version tag.

Practice

1. What is Docker Hub primarily used for in Docker workflows?

easy

A. A public registry to store and share Docker images

B. A tool to build Docker images locally

C. A command-line interface for managing containers

D. A service to monitor running Docker containers

Solution

1. Step 1: Understand Docker Hub's role

   Docker Hub is a cloud-based service where users can upload and download Docker images.

2. Step 2: Differentiate from other Docker tools

   Building images is done locally with Docker CLI, not Docker Hub. Docker Hub is for storing and sharing images.

3. Final Answer:

   A public registry to store and share Docker images -> Option A

4. Quick Check:

   Docker Hub = Image registry [OK]

Hint: Docker Hub = place to store/share images [OK]

Common Mistakes:

• Confusing Docker Hub with Docker CLI commands
• Thinking Docker Hub builds images
• Assuming Docker Hub manages running containers

2. Which command correctly logs you into Docker Hub from the terminal?

easy

A. docker login

B. docker push

C. docker pull

D. docker build

Solution

1. Step 1: Identify the login command

   The command docker login prompts for Docker Hub credentials to authenticate the user.

2. Step 2: Understand other commands

   docker push uploads images, docker pull downloads images, and docker build creates images locally.

3. Final Answer:

   docker login -> Option A

4. Quick Check:

   Login command = docker login [OK]

Hint: Use 'docker login' to authenticate with Docker Hub [OK]

Common Mistakes:

• Using 'docker push' to login
• Confusing 'docker pull' with login
• Trying to login with 'docker build'

3. What will happen if you run docker push myuser/myapp:latest without logging into Docker Hub first?

medium

A. Docker will create a new repository automatically

B. Docker will prompt for login credentials

C. The image will be pushed successfully

D. The command will fail with an authentication error

Solution

1. Step 1: Understand authentication requirement for push

   Pushing images to Docker Hub requires authentication; without login, Docker cannot verify permissions.

2. Step 2: Result of pushing without login

   Docker will reject the push and show an authentication error instead of prompting or succeeding.

3. Final Answer:

   The command will fail with an authentication error -> Option D

4. Quick Check:

   Push without login = auth error [OK]

Hint: Push needs login; no login causes auth error [OK]

Common Mistakes:

• Expecting Docker to prompt for login automatically
• Assuming push works without authentication
• Thinking Docker creates repos automatically on push

4. You tried to push an image with docker push myuser/myapp but got an error: denied: requested access to the resource is denied. What is the most likely cause?

medium

A. You forgot to tag the image with your Docker Hub username

B. Docker daemon is not running

C. You are not logged into Docker Hub or lack permission

D. The image name contains invalid characters

Solution

1. Step 1: Analyze the error message

   The error means Docker Hub rejected access, usually due to missing login or permission issues.

2. Step 2: Check common causes

   Not being logged in or lacking rights to push to that repository causes this error, even if tagging is correct.

3. Final Answer:

   You are not logged into Docker Hub or lack permission -> Option C

4. Quick Check:

   Access denied = login or permission issue [OK]

Hint: Access denied usually means login or permission problem [OK]

Common Mistakes:

• Assuming tagging is always the cause
• Ignoring login status
• Thinking Docker daemon stopped causes this error

5. You want to share a custom Docker image named myapp with your team using Docker Hub. Which sequence of commands correctly tags and pushes the image to your Docker Hub repository myuser/myapp?

hard

A. docker login && docker build myapp && docker push myuser/myapp

B. docker tag myapp myuser/myapp:latest && docker push myuser/myapp:latest

C. docker push myapp && docker tag myuser/myapp:latest

D. docker pull myapp && docker tag myuser/myapp && docker push

Solution

1. Step 1: Tag the local image with your Docker Hub repo name

   Use docker tag myapp myuser/myapp:latest to prepare the image for pushing.

2. Step 2: Push the tagged image to Docker Hub

   Run docker push myuser/myapp:latest to upload the image to your Docker Hub repository.

3. Final Answer:

   docker tag myapp myuser/myapp:latest && docker push myuser/myapp:latest -> Option B

4. Quick Check:

   Tag then push = correct sequence [OK]

Hint: Tag image with repo name before pushing [OK]

Common Mistakes:

• Pushing without tagging the image
• Pushing before tagging or building
• Confusing pull with push commands