Use Ubuntu to run a single command
The run command allows us to launch a Docker container based on an image. The --rm flag tells Docker to remove the container from ou harddisk once it stopped running. It is a good idea to do so if you don't need the conatainer any more. Otherwise the dead containers would just accumulate and take up disk space.
After the name of the image we can also provide the command line that needs to be execute. In this case echo hello is just a simple shell command.
Running this will print hello and then the conatiner will exit and it will be removed from the disk as if it never existed.
docker run --rm ubuntu:20.04 echo hello