When you put Docker inside Docker, the inner Docker doesn’t have access to the outer Docker’s cache. It would be wicked sweet to have access to the parent Docker’s cache from the nested inner Docker. I am interested in this for building full scale models of data center system infrastructure.
docker pull python:3.4
docker run --expose-cache -it python:3.4 bash
apt-get update; apt-get install docker.io -y;
docker pull python:3.4 # *** this would be fast utilizing the parent unionfs cache layers… ***