I've been playing around with docker images recently. I saw this docker doc on using FROM scratch. I am trying to see how far I can take this just for fun. I program in python. The doc says to compile the example C program to a binary, copy it to the container and then run it. In the container, I can not run python <program_file>. I saw this stack exchange post about compiling a python file to a binary, which meets our test use case here. It mentions using pyinstaller. So I run it on a test hello.py file which justs prints Hello with pyinstaller hello.py and I get a bunch of messages about building the projects. Okay, good. I can run the binary in my local machine by running "dist/hello" (this is the binary program mentioned by the post. So I write my Dockerfile to copy this program over and run it. My Dockerfile is
FROM scratch
ADD dist/hello /
CMD ["./hello"]
I run docker build . -t "hello:1.0" and then docker run hello:1.0 and....
I get an error messgage:
standard_init_linux.go:211: exec user process caused "no such file or directory"
What gives? What did I go wrong? Is it possible to get pyinstaller to compile a binary python project (multiple files, instead of just this one), then use the scratch image to run it. Are there any caveats if this is possible?
So the answer is to use Google's distroless image. They have an example on their github that I have slightly edited as follows.:
# Build a virtualenv using the appropriate Debian release
# * Install python3-venv for the built-in Python3 venv module (not installed by default)
# * Install gcc libpython3-dev to compile C Python modules
# * Update pip to support bdist_wheel
FROM debian:buster-slim AS build
RUN apt-get update && \
apt-get install --no-install-suggests --no-install-recommends --yes python3-venv gcc libpython3-dev && \
python3 -m venv /venv && \
/venv/bin/pip install --upgrade pip
# Build the virtualenv as a separate step: Only re-execute this step when requirements.txt changes
FROM build AS build-venv
COPY requirements.txt /requirements.txt
RUN /venv/bin/pip install --disable-pip-version-check -r /requirements.txt
# Copy the virtualenv into a distroless image
FROM gcr.io/distroless/python3-debian10
COPY --from=build-venv /venv /venv
COPY . /app
WORKDIR /app
ENTRYPOINT ["/venv/bin/python3", "hello.py"]
Just posting this in case someone is wondering. Definitely a cool thing.