# Demonstration: One Image, Many Independent Containers

## OBSERVE

```
$ docker images | grep alpine
alpine   3.19   a1b2c3d4e5f6   2 weeks ago   7.4MB
```

Exactly one `alpine:3.19` image exists locally right now.

## HYPOTHESIS

Predict: after running three containers from it, how many images will `docker images` show?

## INSPECT

```
$ docker run -d --name c1 alpine:3.19 sleep 300
$ docker run -d --name c2 alpine:3.19 sleep 300
$ docker run -d --name c3 alpine:3.19 sleep 300
$ docker images | grep alpine
alpine   3.19   a1b2c3d4e5f6   2 weeks ago   7.4MB
```

Still exactly one image — confirmed.

## CHANGE

```
$ docker ps --format '{{.Names}}: {{.ID}}'
c3: 9f8e7d6c5b4a
c2: 3d2c1b0a9f8e
c1: 7c6b5a4d3e2f
```

Three DIFFERENT containers, each with its own ID, all created from that same one image.

## VERIFY

```
$ docker rm -f c1 c2 c3
$ docker images | grep alpine
alpine   3.19   a1b2c3d4e5f6   2 weeks ago   7.4MB
```

Removing all three containers left the image completely untouched — proving containers and the
image they came from have independent lifecycles.

## Instructor Notes

**Demo goal:** Make the 1-image-many-containers relationship undeniable by actually counting
both before and after, rather than just stating it.

**Approximate timing:** 8 minutes live.

**Common mistake to watch for:** assuming `docker rm` on a container also removes its image —
a good moment to reinforce that images and containers have separate removal commands
(`docker rm` for containers, `docker rmi` for images) for exactly this reason.