So I'm quite new to Docker, hence apologies if this is a bit of a newbie question...
I've just build my first app using Docker (python 3 flask web app) and it works great.
However, something I noticed when I ran
docker images -a
Docker uses a layered file system. When you have a Dockerfile, Docker creates for each instruction (like FROM, RUN or ADD) a new layer to the image (what you see in your screenshot). The advantage of layers is, that they can be reused.
For example, if you have two images, which both run a program on Ubuntu, Docker can reuse the Ubuntu image instead of creating a new one and thus saves disk space. The size shown by
docker images -a represents the virtual size and not the real size. So, your
altum-platform is 1.43 GB big and not 4x 1.43 GB. For more information look here.