Container disk usage management in Docker - Step-by-Step Execution

Process Flow - Container disk usage management

Start: Check disk usage

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Run 'docker system df'

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Analyze output: Images, Containers, Volumes

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Decide cleanup action

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Remove unused images

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Remove stopped containers

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Remove unused volumes

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Run cleanup commands

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Verify disk usage reduced

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End

The flow shows checking disk usage, analyzing what takes space, choosing cleanup steps, running cleanup, and verifying results.

Execution Sample

Docker

docker system df
docker image prune -a
docker container prune
docker volume prune

This sequence checks disk usage, then removes unused images, stopped containers, and unused volumes.

Process Table

Step	Command Run	Action	Output Summary	Disk Usage Change
1	docker system df	Check disk usage	Shows space used by images, containers, volumes	No change
2	docker image prune -a	Remove all unused images	Deleted 3 images, freed 1.2GB	Disk usage decreased
3	docker container prune	Remove stopped containers	Deleted 2 containers, freed 500MB	Disk usage decreased
4	docker volume prune	Remove unused volumes	Deleted 1 volume, freed 300MB	Disk usage decreased
5	docker system df	Verify disk usage	Shows reduced space usage	Confirmed decrease
6	-	End	Cleanup complete	Final disk usage reduced

💡 Cleanup commands run and disk usage verified to be reduced.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Images (count)	10	7	7	7	7
Containers (stopped count)	5	5	3	3	3
Volumes (unused count)	4	4	4	3	3
Disk Usage (GB)	5.0	3.8	3.3	3.0	3.0

Key Moments - 3 Insights

Why does 'docker image prune -a' remove more images than just 'docker image prune'?

'docker image prune -a' removes all unused images including dangling and unreferenced ones, as shown in step 2 where 3 images are deleted, while 'docker image prune' removes only dangling images.

Why do we run 'docker system df' before and after cleanup?

Running 'docker system df' before shows current disk usage, and after cleanup confirms the disk space was freed, as seen in steps 1 and 5.

Does 'docker container prune' remove running containers?

No, it only removes stopped containers, which is why container count decreases from 5 to 3 after step 3.

Visual Quiz - 3 Questions

Look at the execution table, how many images were deleted after running 'docker image prune -a'?

A 5

B 2

C 3

D 0

💡 Hint

Check the 'Output Summary' column in step 2 of the execution table.

At which step does the disk usage first decrease?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Disk Usage Change' column in the execution table.

If no stopped containers existed, how would the 'docker container prune' step change?

A It would delete zero containers and free no space

B It would delete volumes instead

C It would delete containers anyway

D It would fail with an error

💡 Hint

Refer to the action and output in step 3 of the execution table.

Concept Snapshot

Container Disk Usage Management:
- Use 'docker system df' to check disk space used by images, containers, volumes.
- Clean unused data with 'docker image prune -a', 'docker container prune', 'docker volume prune'.
- Always verify disk usage after cleanup.
- Prune commands remove only unused or stopped resources.
- Regular cleanup prevents disk space issues.

Full Transcript

This visual execution shows how to manage disk usage in Docker containers. First, we check disk usage with 'docker system df' to see how much space images, containers, and volumes use. Then, we run cleanup commands: 'docker image prune -a' removes all unused images, 'docker container prune' removes stopped containers, and 'docker volume prune' removes unused volumes. After each cleanup, disk usage decreases as shown in the output summaries. Finally, we verify the disk usage again with 'docker system df' to confirm space was freed. Key points include understanding that prune commands only remove unused or stopped resources and that checking usage before and after cleanup helps confirm success.