Docker whale (create Docker image)

Create Dockerfile with the following content:

FROM docker/whalesay:latest
RUN apt-get -y update && apt-get install -y fortunes
CMD /usr/games/fortune -a | cowsay

$ docker build -t docker-whale .
...

$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
docker-whale        latest              d5cf6bf32c0f        24 seconds ago      277 MB
hello-world         latest              48b5124b2768        6 weeks ago         1.84 kB
docker/whalesay     latest              6b362a9f73eb        21 months ago       247 MB

The command docker ps -a shows nothing new.