With the setup accomplished, we can use the local Docker instance to create Docker containers, run a few commands, and, in general, learn how to use this amazing system.

As in so many software journeys, this one starts with saying Hello World:

$ docker run hello-world  
Unable to find image 'hello-world:latest' locally 
latest: Pulling from library/hello-world 
ca4f61b1923c: Pull complete  
Digest: sha256:66ef312bbac49c39a89aa9bcc3cb4f3c9e7de3788c944158df3ee0176d32b751 
Status: Downloaded newer image for hello-world:latest 
 
Hello from Docker! 
This message shows that your installation appears to be working correctly. 
 
To generate this message, Docker took the following steps: 
 1. The Docker client contacted the Docker daemon. 
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub. 
    (amd64) 
 3. The Docker daemon created a new container from that image which runs the 
    executable that produces the output you are currently reading. 
 4. The Docker daemon streamed that output to the Docker client, which sent it 
    to your terminal. 
 
To try something more ambitious, you can run an Ubuntu container with: 
 $ docker run -it ubuntu bash 
 
Share images, automate workflows, and more with a free Docker ID: 
 https://cloud.docker.com/ 
 
For more examples and ideas, visit: 
 https://docs.docker.com/engine/userguide/

The docker run command downloads a Docker image, named on the command line, initializes a Docker container from that image, and then runs that container. In this case, the image, named hello-world, was not present on the local computer and had to be downloaded and initialized. Once that was done, the hello-world container was executed and it printed out these instructions.

You can query your computer to see that while the hello-world container has executed and finished, it still exists:

The docker ps command lists the running Docker containers. As we see here, the hello-world container is no longer running, but with the -a switch, docker ps also shows those containers that exist but are not currently running. We also see that this computer has a Nextcloud instance installed along with its associated database.

When you're done using a container, you can clean up with the following command:

$ docker rm boring_lumiere
boring_lumiere

The name boring_lumiere is the container name automatically generated by Docker. While the image name was hello-world, that's not the container name. Docker generated the container name so you have a more user-friendly identifier for the containers than the hex ID shown in the container ID column. When creating a container, it's easy to specify any container name you like.