The hello-world container

Learn to test the install by running the first container.

What does hello-world prove?

The output of the hello-world container tells you four steps completed successfully in the background:

The CLI connected to the daemon.
The daemon pulled the image from Docker Hub.
The daemon created a new container from the image and ran the program.
The daemon streamed the output to the CLI, which sent it to the terminal.

docker run hello-world

Stopped containers pile up

hello-world stops when it finishes but isn't removed. docker ps -a also shows stopped containers; every run adds a new one. You need to use --rm or clean up with docker container prune:

$ docker ps -a
CONTAINER ID   IMAGE         STATUS                     NAMES
a1b2c3d4e5f6   hello-world   Exited (0) 5 seconds ago   jolly_tesla
$ docker container prune -f

Exercise Try and clean up

Write three commands: run hello-world; list all containers (including stopped ones); clean up the stopped containers without asking for confirmation.

Show example solution

docker run hello-world
docker ps -a
docker container prune -f

Test yourself

What is different when hello-world is run a second time?
- The same container is reused
- The output becomes Turkish
- The download step is skipped because the image is local
- It gives an error
Show answer

The download step is skipped because the image is local — Each docker run creates a new container; the image comes from the cache.
List stopped containers too.
```
docker ps ____
```
Show answer
```
docker ps -a
```
Match.

Exited (0)

Finished successfully
docker ps -a

All containers
container prune

Removes stopped ones
jolly_tesla

Automatically given name

Next lesson: Docker Desktop

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