System prune for cleanup in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the command docker system prune -f?

You run docker system prune -f on a system with unused containers, networks, images, and build cache. What will this command do?

Docker

docker system prune -f

A Only shows what would be removed without actually deleting anything.

B Removes only stopped containers and unused networks, but keeps images and build cache.

C Removes all containers, including running ones, and all images.

D Removes all stopped containers, unused networks, dangling images, and build cache without asking for confirmation.

💡 Hint

The -f flag forces the prune without confirmation.

The docker system prune -f command cleans up all unused data including stopped containers, unused networks, dangling images, and build cache without asking for confirmation.

✅ Best Practice

intermediate

Which option is the safest way to clean up unused Docker resources without affecting running containers?

You want to free disk space by removing unused Docker resources but must not stop or remove any running containers. Which command should you use?

A docker system prune -f

B docker system prune -a -f

C docker container prune -f

D docker image prune -a -f

💡 Hint

Consider what resources each prune command affects.

docker system prune -f removes stopped containers, unused networks, dangling images, and build cache but does not affect running containers.

❓ Troubleshoot

advanced

Why does docker system prune not remove some unused images?

You ran docker system prune -f but noticed some unused images remain. What is the most likely reason?

A The command requires the <code>--all</code> flag to remove any images.

B The images are corrupted and cannot be removed.

C The images are tagged and not dangling, so they are not removed by default.

D Docker daemon is not running, so prune has no effect.

💡 Hint

Think about what 'dangling' means for images.

By default, docker system prune removes only dangling images (untagged). Tagged images are kept unless --all is specified.

🔀 Workflow

advanced

What is the correct sequence to safely clean up all unused Docker images, including untagged and tagged, without affecting running containers?

Arrange the following commands in the correct order to clean up all unused Docker images and other unused resources safely.

A 1,3,2,4

B 4,1,3,2

C 1,2,3,4

D 3,1,4,2

💡 Hint

Start by pruning containers and networks before images and system prune.

First remove stopped containers, then unused networks, then all unused images including tagged ones, and finally run system prune to clean build cache and any leftovers.

🧠 Conceptual

expert

What is the effect of running docker system prune --volumes -f?

You execute docker system prune --volumes -f. What additional cleanup does this command perform compared to docker system prune -f?

A It removes only volumes and leaves containers, networks, and images untouched.

B It removes all unused volumes in addition to stopped containers, unused networks, dangling images, and build cache.

C It removes volumes but requires confirmation even with <code>-f</code> flag.

D It removes volumes only if they are attached to running containers.

💡 Hint

Volumes are not removed by default with system prune.

The --volumes flag adds removal of all unused volumes to the standard system prune cleanup.