Container disk usage management in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to list disk usage of Docker images.

Docker

docker system [1]

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

Adf

Bimages

Cprune

Dps

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prune' which deletes unused data instead of showing usage.

Using 'images' which lists images but does not show disk usage.

Using 'ps' which lists containers but not disk usage.

The docker system df command shows disk usage of Docker images, containers, and volumes.

2fill in blank

medium

Complete the command to remove all stopped containers and unused images.

Docker

docker system [1]

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

Adf

Brm

Cprune

Dclean

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'df' which only shows disk usage.

Using 'rm' which removes specific containers or images but not system-wide.

Using 'clean' which is not a valid Docker command.

The docker system prune command removes all stopped containers, unused networks, dangling images, and build cache.

3fill in blank

hard

Fix the error in the command to remove dangling images.

Docker

docker image rm $(docker images -f "dangling=[1]" -q)

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

Atrue

Bfalse

Cnone

Dall

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'false' which selects non-dangling images.

Using 'none' or 'all' which are invalid filter values.

To remove dangling images, the filter dangling=true is used to select images not tagged and unused.

4fill in blank

hard

Fill both blanks to create a command that removes all unused volumes and networks.

Docker

docker volume [1] && docker network [2]

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

Aprune

Brm

Clist

Dinspect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'rm' which removes specific named resources, not all unused ones.

Using 'list' or 'inspect' which only show information.

The docker volume prune and docker network prune commands remove all unused volumes and networks respectively.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps container IDs to their size if size is greater than 100MB.

Docker

sizes = [1]: [2] for c in containers if c['SizeRootFs'] [3] 100*1024*1024

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

Ac['Id']

Bc['SizeRootFs']

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' which selects smaller containers.

Using wrong keys or values that do not exist.

This comprehension creates a dictionary with container IDs as keys and their sizes as values, filtering only those larger than 100MB.

Practice

1. What does the docker system df command show you?

easy

A. The disk space used by Docker images, containers, and volumes

B. The list of running Docker containers

C. The network settings of Docker containers

D. The logs of a specific Docker container

Solution

1. Step 1: Understand the purpose of docker system df and compare options

   This command summarizes disk usage by Docker objects like images, containers, and volumes. Options B (docker ps), C (network settings), and D (logs) describe unrelated commands.

2. Final Answer:

   The disk space used by Docker images, containers, and volumes -> Option A

3. Quick Check:

   Disk usage summary = A [OK]

Hint: Remember 'df' means disk free or usage summary [OK]

Common Mistakes:

• Confusing disk usage with container status
• Thinking it shows logs or network info
• Using it to list running containers

2. Which of the following commands correctly removes only all stopped containers to free disk space?

easy

A. docker container prune

B. docker image rm $(docker images -q)

C. docker system prune -a

D. docker container rm -f $(docker ps -a -q)

Solution

1. Step 1: Identify command to remove only stopped containers and check options

   docker container prune safely removes all stopped containers only. A forcibly removes all containers (running and stopped). B removes images. C removes stopped containers plus unused images and networks (more than containers).

2. Final Answer:

   docker container prune -> Option A

3. Quick Check:

   Remove stopped containers = D [OK]

Hint: Use prune commands to safely clean stopped containers [OK]

Common Mistakes:

• Using force remove on all containers including running ones
• Confusing image removal with container removal
• Using system prune when only containers should be removed

3. What will be the output of the command docker system df after running docker image prune -a?

medium

A. Error message about running containers

B. Disk usage report showing fewer images and freed space

C. List of all images including unused ones

D. No change in disk usage report

Solution

1. Step 1: Understand docker image prune -a effect on docker system df

   This removes all unused images, freeing space, so the report shows fewer images and more free space. No error, no list, and usage changes.

2. Final Answer:

   Disk usage report showing fewer images and freed space -> Option B

3. Quick Check:

   Image prune frees space = B [OK]

Hint: Prune unused images to reduce disk usage [OK]

Common Mistakes:

• Expecting an error when pruning images
• Thinking prune lists images instead of removing
• Assuming no change in disk usage after prune

4. You ran docker volume prune but still see high disk usage. What could be the reason?

medium

A. The prune command only cleans network settings

B. The prune command deleted running containers by mistake

C. Docker does not track volume disk usage

D. There are unused images and stopped containers still taking space

Solution

1. Step 1: Understand docker volume prune and reason for remaining usage

   It removes unused volumes only. Unused images and stopped containers remain, causing high usage. No deletion of running containers or network cleaning.

2. Final Answer:

   There are unused images and stopped containers still taking space -> Option D

3. Quick Check:

   Volume prune only removes volumes = A [OK]

Hint: Prune volumes only frees volume space, check images and containers too [OK]

Common Mistakes:

• Assuming volume prune deletes containers
• Thinking prune affects network settings
• Believing Docker ignores volume disk usage

5. You want to free maximum disk space but keep your running containers and their data intact. Which command should you use?

hard

A. docker container rm -f $(docker ps -q)

B. docker system prune --volumes

C. docker system prune -a --volumes

D. docker image rm $(docker images -q)

Solution

1. Step 1: Analyze options for maximum safe cleanup

   docker system prune -a --volumes removes all stopped containers, all unused images (not just dangling), unused networks, and unused volumes--maximizing space--while keeping running containers and their data intact. C frees less (no -a). A removes running containers. D only images, unsafely and incompletely.

2. Final Answer:

   docker system prune -a --volumes -> Option C

3. Quick Check:

   Max prune safely, keep running containers = B [OK]

Hint: Use system prune with volumes to clean safely without stopping containers [OK]

Common Mistakes:

• Using prune without -a flag, freeing less space
• Force removing running containers causing downtime
• Removing images only without cleaning volumes or containers