[vel0city]

I think there's a bit of mix up between what an image is and what a container is. You normally don't write data to an image, but you can write data to the container. You can keep this data so long as you keep the container, and you can commit that container's data to the image if you wish.

I've found a good place to visualize how the filesystems work was this blog: http://merrigrove.blogspot.com/2015/10/visualizing-docker-co...