Dockerfile: ADD vs COPY - CenturyLink Cloud Developer Center

Dockerfile: ADD vs COPY - CenturyLink Cloud Developer Center

Here we have an ADD instruction which retrieves a package from a URL followed by a RUN instruction which unpacks it, builds it and then attempts to clean-up the downloaded archive.

Unfortunately, since the package retrieval and the rm command are in separate image layers we don't actually save any space in our final image (for a more detailed explanation of this phenomenon, see my Optimizing Docker Images article).

In this case you're better off doing something like this:

RUN curl http://foo.com/package.tar.bz2 \    | tar -xjC /tmp/package \    && make -C /tmp/package  

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