Can someone well versed in Docker explain in their own words what this does and why it is useful? Thanks in advance! I'm definitely not a docker poweruser...other than build start and stopping..
If two Dockerfiles use debain:stretch-slim as their base, docker won't download both base images twice. Each command in the Dockerfile creates an image. If you copy a Dockerfile and just change the last line and build them in order, the 2nd build will run a lot faster and you'll see in the output it pulls out "cached images" since it's already run those commands (docker build --no-cache always forced a full build).
If you start making Dockerfiles and playing around with it, it will start to make more sense.
