System prune for cleanup in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to remove all unused Docker objects.

Docker

docker system [1]

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

Arun

Bprune

Cbuild

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker system build' which builds images, not cleans up.

The docker system prune command removes all unused containers, networks, images, and optionally volumes.

2fill in blank

medium

Complete the command to remove unused Docker images only.

Docker

docker image [1]

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

Arun

Bpull

Cprune

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker image run' which runs containers, not cleans images.

The docker image prune command removes unused images to free up space.

3fill in blank

hard

Fix the error in the command to prune all unused Docker objects including volumes.

Docker

docker system prune [1]

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

A--volumes

B--all

C--force

D--interactive

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--all' which removes all unused images, not volumes.

The --volumes flag tells Docker to also remove unused volumes during prune.

4fill in blank

hard

Fill both blanks to prune unused containers and images without confirmation.

Docker

docker system prune [1] [2]

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

A--force

B--all

C--volumes

D--filter

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--volumes' which removes volumes, not required here.

Using --force skips confirmation, and --all removes all unused images as well as containers.

5fill in blank

hard

Fill all three blanks to prune unused containers, images, and volumes without confirmation.

Docker

docker system prune [1] [2] [3]

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

A--force

B--all

C--volumes

D--filter

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--filter' which is for selective pruning, not full cleanup.

--force skips confirmation, --all removes all unused images, and --volumes removes unused volumes.

Practice

1. What does the Docker command docker system prune do?

easy

A. Stops all running containers immediately

B. Removes all unused containers, networks, images, and optionally volumes to free disk space

C. Updates Docker to the latest version

D. Creates a backup of all Docker images

Solution

1. Step 1: Understand the purpose of system prune

   The docker system prune command is designed to clean up unused Docker data like stopped containers, unused networks, dangling images, and optionally volumes.

2. Step 2: Identify what the command removes

   It removes unused resources to free disk space but does not stop running containers or update Docker.

3. Final Answer:

   Removes all unused containers, networks, images, and optionally volumes to free disk space -> Option B

4. Quick Check:

   System prune cleans unused Docker data = A [OK]

Hint: System prune cleans unused Docker data to free space [OK]

Common Mistakes:

• Thinking it stops running containers
• Confusing it with Docker update commands
• Assuming it creates backups

2. Which of the following is the correct syntax to remove all unused images, containers, networks, and volumes with Docker system prune?

easy

A. docker system prune --all --volume

B. docker prune system -a --volumes

C. docker system prune -a --volumes

D. docker system prune -all -volumes

Solution

1. Step 1: Recall correct Docker system prune syntax

   The correct command to remove all unused images, containers, networks, and volumes is docker system prune -a --volumes. The -a flag removes all unused images, and --volumes removes unused volumes.

2. Step 2: Identify syntax errors in other options

   Options A, B, and D have incorrect command order or wrong flags like prune system or misspelled flags.

3. Final Answer:

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

4. Quick Check:

   Correct flags and order = C [OK]

Hint: Use '-a' and '--volumes' flags with 'docker system prune' [OK]

Common Mistakes:

• Swapping 'system' and 'prune' keywords
• Using incorrect flag names like '--volume'
• Omitting the dash in flags

3. What will be the output after running docker system prune -a --volumes if you have 2 stopped containers, 3 unused images, 1 unused volume, and 1 unused network?

medium

A. No resources removed because containers are stopped

B. Removed 2 containers and 3 images only

C. Removed only unused volumes

D. Removed 2 containers, 3 images, 1 volume, and 1 network

Solution

1. Step 1: Understand what the command removes

   The command docker system prune -a --volumes removes all unused containers (including stopped), all unused images, unused volumes, and unused networks.

2. Step 2: Apply to given resources

   Given 2 stopped containers, 3 unused images, 1 unused volume, and 1 unused network, all will be removed by this command.

3. Final Answer:

   Removed 2 containers, 3 images, 1 volume, and 1 network -> Option D

4. Quick Check:

   All unused resources removed = A [OK]

Hint: System prune with '-a' and '--volumes' removes all unused resources [OK]

Common Mistakes:

• Thinking stopped containers are not removed
• Assuming volumes are not removed without extra flag
• Confusing networks with containers

4. You ran docker system prune -a --volumes but received an error: unknown flag: --volumes. What is the likely cause?

medium

A. Docker version is outdated and does not support the --volumes flag

B. You need to run the command as root user

C. The flag should be --volume without 's'

D. You must stop all containers before pruning

Solution

1. Step 1: Analyze the error message

   The error unknown flag: --volumes indicates Docker does not recognize the flag, likely due to an older Docker version.

2. Step 2: Check other options

   Running as root is not required for this flag error. The correct flag is --volumes (with 's'), and stopping containers is not mandatory for the flag to work.

3. Final Answer:

   Docker version is outdated and does not support the --volumes flag -> Option A

4. Quick Check:

   Flag error means outdated Docker = D [OK]

Hint: Update Docker if flags are unrecognized [OK]

Common Mistakes:

• Mistaking flag spelling as the cause
• Assuming root user is required
• Thinking containers must be stopped first

5. You want to free up disk space but keep volumes because they contain important data. Which command should you run?

hard

A. docker system prune

B. docker system prune -a --volumes

C. docker system prune --volumes

D. docker system prune -all -volumes

Solution

1. Step 1: Understand volume preservation

   Volumes store important data and are not removed by default with docker system prune. The --volumes flag explicitly removes unused volumes.

2. Step 2: Choose command that keeps volumes

   Running docker system prune without -a or --volumes removes stopped containers, unused networks, and dangling images but keeps volumes and unused images.

3. Final Answer:

   docker system prune -> Option A

4. Quick Check:

   Default prune keeps volumes = B [OK]

Hint: Avoid '--volumes' to keep volumes safe [OK]

Common Mistakes:

• Using '-a' removes all unused images
• Adding '--volumes' deletes volumes
• Assuming default prune removes volumes