Docker build is not using cache

Question

docker build is not using it\'s cache.

docker build -f Dockerfile .

generates the same output that this does:

doc         


        

Answer 1

From your Dockerfile, if you append lines to your Dockerfile, or change the code being built, there's only one line that could be cached:

RUN mkdir /code

After that, you perform a:

COPY . /code

Since you have changed your Dockerfile, the contents of . have changed (the Dockerfile is part of .) and therefore the COPY needs to be performed again, generating a new layer. Once you generate a new layer, every following layer no longer has a cache and needs to be rebuild.

To improve caching, consider placing the lines that change less towards the top of your Dockerfile. That would leave the COPY . /code line at the very end of the file since it will change almost every time.