System prune for cleanup in Docker - Step-by-Step Execution

Process Flow - System prune for cleanup

Start: Docker system prune command

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Check for unused containers

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Check for unused images

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Check for unused networks

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Check for unused build cache

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Remove all unused data

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Display freed space

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End

The system prune command checks for unused Docker data like containers, images, networks, and cache, then removes them to free space.

Execution Sample

Docker

docker system prune -f

This command removes all unused containers, images, networks, and build cache without asking for confirmation.

Process Table

Step	Action	Evaluation	Result
1	Run 'docker system prune -f'	Identify unused containers	List of stopped containers found
2	Remove unused containers	Containers removed	Space freed from containers
3	Identify unused images	Dangling and unused images found	List of images to remove
4	Remove unused images	Images deleted	Space freed from images
5	Identify unused networks	Networks not used by any container found	List of networks to remove
6	Remove unused networks	Networks deleted	Space freed from networks
7	Identify build cache	Build cache found	Cache to remove
8	Remove build cache	Cache deleted	Space freed from cache
9	Display total space freed	Summary shown	User sees total disk space reclaimed
10	End	No more unused data	Cleanup complete

💡 All unused containers, images, networks, and build cache removed; system cleaned.

Status Tracker

Resource Type	Start	After Prune
Containers (stopped)	3 stopped containers	0 stopped containers
Images (unused)	5 dangling images	0 dangling images
Networks (unused)	2 unused networks	0 unused networks
Build Cache	Some cache data	No cache data

Key Moments - 3 Insights

Why does the command remove stopped containers but not running ones?

The prune command only targets unused resources. Running containers are in use, so they are not removed. See execution_table rows 1 and 2 where only stopped containers are identified and removed.

What does the '-f' flag do in 'docker system prune -f'?

The '-f' flag forces the prune without asking for confirmation. This is why the command proceeds directly to removal steps in the execution_table without pause.

Does 'docker system prune' remove volumes?

By default, volumes are not removed. The command targets containers, images, networks, and build cache only. This is why volumes are not listed in the variable_tracker or execution_table.

Visual Quiz - 3 Questions

Look at the execution table, at which step are unused images removed?

A Step 5

B Step 3

C Step 4

D Step 2

💡 Hint

Check the 'Action' column for image removal in the execution_table.

According to the variable tracker, how many stopped containers remain after prune?

A 3

B 0

C 1

D 5

💡 Hint

Look at the 'Containers (stopped)' row under 'After Prune' in variable_tracker.

If the '-f' flag is removed, what changes in the execution flow?

A The command will ask for confirmation before removal

B It will remove volumes as well

C It will skip removing networks

D It will remove running containers

💡 Hint

Recall the explanation about the '-f' flag in key_moments and how it affects confirmation.

Concept Snapshot

docker system prune -f
Removes all unused containers, images, networks, and build cache
Does not remove volumes by default
-f skips confirmation prompt
Frees disk space by cleaning unused Docker data

Full Transcript

The 'docker system prune -f' command cleans up unused Docker resources. It first finds stopped containers, unused images, networks, and build cache. Then it removes them all without asking for confirmation because of the '-f' flag. Running containers and volumes are not removed. After completion, it shows how much disk space was freed. This helps keep your Docker environment clean and saves storage space.