apt remove in Docker layers will no twork

Hi Sören

Line 39 in 7fe0dae

RUN apt-get remove -y \

this will not work, if you want to save image sizes
because Docker images are composed in layers

every RUN command is one layer and will be safed (like in git)

you need to COPY first and merge the RUN commands in to one big command
then you can apt remove the packages as last (all in the same Docker layer)

SECOND OPTION (better)

install and compile all in an build layer

https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds

notice COPY --from=0 /go/src/github.com/alexellis/href-counter/app .

you will copy the compiled files to a clean new image
and the build layer will be erased

CLI TOOLS TO RESCUE

https://github.com/wagoodman/dive - to inspect docker layer to shrink image size
https://github.com/hadolint/hadolint - Dockerfile linter

ah

and try to take debian:stretch-slim this will safe also some MB

and http://download.oracle.com/berkeley-db/db-4.8.30.tar.gz should not be hard coded

move the url in a variable

ARG BERKLY_PKG_URL=http://download.oracle.com/berkeley-db/db-4.8.30.tar.gz

# Install Berkeley DB 4.8
RUN curl -L $BERKLY_PKG_URL | tar -xz -C /tmp && \

you can pass parameters to the docker build command via --build-arg

docker build -t xsn-test-build --build-arg BERKLY_PKG_URL=http://download.oracle.com/berkeley-db/db-4.8.30.tar.gz .

PR open

#149