What is Docker - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run a Docker container from the nginx image.

Docker

docker run [1] nginx

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

A-d

B-p

C--rm

D-v

Attempts:

3 left

💡 Hint

Common Mistakes

Using -p instead of -d runs the container with port mapping, not detached.

The -d option runs the container in detached mode, meaning it runs in the background.

2fill in blank

medium

Complete the command to list all Docker containers, including stopped ones.

Docker

docker ps [1]

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

A-l

B-a

C-q

D-s

Attempts:

3 left

💡 Hint

Common Mistakes

Using -l shows only the last created container.

The -a option shows all containers, including those that are stopped.

3fill in blank

hard

Fix the error in the command to build a Docker image from a Dockerfile.

Docker

docker build -t [1] .

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

Arun

Bstart

Ccontainer

Dmyimage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'run' or 'start' as image names causes errors.

The -t option tags the image with a name. 'myimage' is a valid image name.

4fill in blank

hard

Fill both blanks to create a Docker volume and mount it to a container.

Docker

docker volume [1] mydata && docker run -v mydata:[2] nginx

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

Acreate

B/data

C/app

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remove' instead of 'create' deletes volumes.

create makes a new volume named 'mydata'. Mounting it to /data inside the container shares the volume.

5fill in blank

hard

Fill all three blanks to write a Dockerfile that uses an alpine base image, copies a file, and runs a command.

Docker

FROM [1]
COPY [2] /app/
CMD ["[3]"]

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

Aalpine

Bscript.sh

Csh

Dubuntu

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ubuntu' as base image changes the image size.

The base image is alpine. We copy script.sh into the container. The command sh runs the shell.

Practice

1. What is the main purpose of Docker?

easy

A. To write code faster using a new programming language

B. To package applications into containers that run consistently everywhere

C. To replace operating systems on servers

D. To create virtual machines for running multiple OS

Solution

1. Step 1: Understand Docker's core function

   Docker packages applications and their dependencies into containers.

2. Step 2: Compare with other options

   The other options describe unrelated technologies or incorrect uses.

3. Final Answer:

   To package applications into containers that run consistently everywhere -> Option B

4. Quick Check:

   Docker = container packaging [OK]

Hint: Docker = app in container for consistent runs [OK]

Common Mistakes:

• Confusing Docker with a programming language
• Thinking Docker replaces the OS
• Mixing Docker with virtual machines

2. Which of the following is the correct command to check the installed Docker version?

easy

A. docker version

B. docker check

C. docker --install

D. docker status

Solution

1. Step 1: Recall Docker commands

   The command to check Docker version is docker version.

2. Step 2: Validate other options

   Commands like docker check, docker --install, and docker status are invalid or do not show version.

3. Final Answer:

   docker version -> Option A

4. Quick Check:

   Check version = docker version [OK]

Hint: Use 'docker version' to see Docker's installed version [OK]

Common Mistakes:

• Using 'docker check' which is not a valid command
• Trying 'docker status' to check version
• Confusing install commands with version check

3. What will be the output of the command docker ps if no containers are running?

medium

A. Displays an empty table with headers but no container entries

B. Shows an error message 'No containers found'

C. Lists all running containers

D. Starts a new container automatically

Solution

1. Step 1: Understand 'docker ps' behavior

   The command docker ps lists running containers. If none are running, it shows headers but no container rows.

2. Step 2: Check other options

   It does not show an error or start containers automatically.

3. Final Answer:

   Displays an empty table with headers but no container entries -> Option A

4. Quick Check:

   docker ps empty = headers only [OK]

Hint: 'docker ps' shows running containers or empty headers if none [OK]

Common Mistakes:

• Expecting an error message when no containers run
• Thinking it starts containers automatically
• Confusing 'docker ps' with 'docker images'

4. You run docker run hello-world but get an error saying the image is not found locally. What should you do to fix this?

medium

A. Delete all containers and try again

B. Reinstall Docker completely

C. Run docker pull hello-world to download the image first

D. Change the command to docker start hello-world

Solution

1. Step 1: Understand the error cause

   The error means the image 'hello-world' is not on your machine.

2. Step 2: Fix by downloading the image

   Use docker pull hello-world to get the image from Docker Hub.

3. Final Answer:

   Run docker pull hello-world to download the image first -> Option C

4. Quick Check:

   Image missing? Use docker pull [OK]

Hint: Pull missing images before running containers [OK]

Common Mistakes:

• Trying to start a container without the image
• Reinstalling Docker unnecessarily
• Deleting containers unrelated to the image issue

5. Which of the following best explains why Docker containers help teams work faster and more reliably?

hard

A. Containers automatically fix bugs in the application code

B. Containers run only on the developer's local machine

C. Containers replace the need for any testing before deployment

D. Containers isolate apps and dependencies, avoiding setup conflicts across environments

Solution

1. Step 1: Understand container benefits

   Docker containers package apps with all needed parts, so they run the same everywhere.

2. Step 2: Evaluate options

   Containers isolate apps and dependencies, avoiding setup conflicts across environments correctly states isolation and consistency. The other options are false or misleading.

3. Final Answer:

   Containers isolate apps and dependencies, avoiding setup conflicts across environments -> Option D

4. Quick Check:

   Isolation + consistency = faster, reliable work [OK]

Hint: Containers isolate apps to avoid environment issues [OK]

Common Mistakes:

• Believing containers fix code bugs automatically
• Skipping testing because of containers
• Thinking containers only run locally