Copy file out of docker image during docker build

Question

I have a simply Dockerfile to build python requirements into a zip file to be uploaded to AWS Lambda.

FROM amazonlinux:2.0.20221004.0

RUN yum install -y python37 && \
    yum install -y python3-pip && \
    yum install -y zip && \
    yum clean all

RUN python3.7 -m pip install --upgrade pip && \
    python3.7 -m pip install virtualenv

COPY aws_requirements.txt .

RUN pip install -r aws_requirements.txt -t ./python
RUN zip -r python.zip ./py

Is there a way to copy the python.zip out of the image to the host during the dockerfile?

Do you also want to create an image? Or is the goal of the build only to create the zip file? — BMitch, Nov 09 '22 at 21:32

score 1 · Accepted Answer · answered Nov 09 '22 at 21:42

With buildkit, you can output the result to a directory on the host instead of pushing to a registry. So you can put the zip file in a scratch image and then output that:

FROM amazonlinux:2.0.20221004.0 as build

RUN yum install -y python37 && \
    yum install -y python3-pip && \
    yum install -y zip && \
    yum clean all

RUN python3.7 -m pip install --upgrade pip && \
    python3.7 -m pip install virtualenv

COPY aws_requirements.txt .

RUN pip install -r aws_requirements.txt -t ./python
RUN zip -r /python.zip ./py

FROM scratch as artifact
COPY --from=build /python.zip /python.zip

Then running:

docker build --output type=local,dest=out .

Will create a out/python.zip file.

Copy file out of docker image during docker build

1 Answers1