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World D1: First Containers

Clean up safely

You will learn: to see what fills your disk, and to clean up without losing what you need.

Checked with Docker Engine 29 on 31 Oct 2026

The problem

Your laptop~

  • No open hatches

Lunchboxes (containers)

  • webrunning
    from nginx:1.30-alpine
  • old1stopped
    from alpine:3.22
  • old2stopped
    from hello-world

Frozen packs (images)

  • alpine:3.221 layers · 12.9MB · in use
  • hello-world:latest1 layers · 25.9kB · in use
  • nginx:1.30-alpine8 layers · 93.5MB · in use
  • redis:8-alpine7 layers · 162MB

Your laptop is filling up. Old boxes and packs pile up, like a messy fridge. docker system df shows what uses the space.

Try it

docker rm throws away a stopped box, and the files inside it. Remove old1 and old2. Keep web.

Your laptop~

  • No open hatches

Lunchboxes (containers)

  • webrunning
    from nginx:1.30-alpine
  • old1stopped
    from alpine:3.22
  • old2stopped
    from hello-world

Frozen packs (images)

  • alpine:3.221 layers · 12.9MB · in use
  • hello-world:latest1 layers · 25.9kB · in use
  • nginx:1.30-alpine8 layers · 93.5MB · in use
  • redis:8-alpine7 layers · 162MB

Watch

Your laptop~

  • No open hatches

Lunchboxes (containers)

  • webrunning
    from nginx:1.30-alpine
  • old1stopped
    from alpine:3.22
  • old2stopped
    from hello-world

Frozen packs (images)

  • alpine:3.221 layers · 12.9MB · in use
  • hello-world:latest1 layers · 25.9kB · in use
  • nginx:1.30-alpine8 layers · 93.5MB · in use
  • redis:8-alpine7 layers · 162MB

docker rmi removes a meal pack. redis goes. hello-world is refused: the real error says a container is using its referenced image. Plain words: remove the box first.

Predict

docker system prune asks: are you sure? What will y delete?

Watch

Your laptop~

  • No open hatches

Lunchboxes (containers)

  • webrunning
    from nginx:1.30-alpine
  • old1stopped
    from alpine:3.22
  • old2stopped
    from hello-world

Frozen packs (images)

  • alpine:3.221 layers · 12.9MB · in use
  • hello-world:latest1 layers · 25.9kB · in use
  • nginx:1.30-alpine8 layers · 93.5MB · in use
  • redis:8-alpine7 layers · 162MB

prune: Sweep away everything unused in one go. It asks first, and there is no undo. sweeps up everything unused. It always asks first. y deletes, and there is no undo. N keeps it all.

Try it

Safe to type any time, or careful? Sort them.

Drag a card into a box. Or tap the card, then tap the box.

      Try it

      Sweep up every stopped box in one go. Read the warning before you answer.

      Your laptop~

      • No open hatches

      Lunchboxes (containers)

      • webrunning
        from nginx:1.30-alpine
      • old1stopped
        from alpine:3.22
      • old2stopped
        from hello-world

      Frozen packs (images)

      • alpine:3.221 layers · 12.9MB · in use
      • hello-world:latest1 layers · 25.9kB · in use
      • nginx:1.30-alpine8 layers · 93.5MB · in use
      • redis:8-alpine7 layers · 162MB

      You did it!

      You can now free space without losing what you need.

      Go deeper (optional)

      Where the story breaks: you cook a real meal pack once. A Docker image is never used up: one pack fills endless boxes. Packs also share layers, so rmi may free less than you expect. Careful: docker volume prune -a deletes saved data (World D3).

      Real mission

      1. docker system df
      2. docker ps -a
      3. docker container prune

      0 of 3 steps done · Your ticks are saved.