Example Dockerfile to use as base

Multistage, state one "FROM base as builder" builds code/libs
- Second stage starts over "FROM base" and copies "--from=builder" files from first container.

example Dockerfile

FROM python:3.7-alpine as base
FROM base as builder
RUN mkdir /install
WORKDIR /install
COPY requirements.txt /requirements.txt
RUN pip install --install-option="--prefix=/install" -r /requirements.txt


FROM base
COPY --from=builder /install /usr/local
COPY src /app
COPY README.md /
WORKDIR /app
#With entrypoint can pass commandline arguments
ENTRYPOINT ["python" , "send-mail.py"]

Dockerfile for serverless aws lambda build

#PES 2020
FROM debian:buster

# Install Python3 with pip and devel
# Install GCC, Make and MySQL-devel, NodeJS, Nano, findutils, and libyaml for parsing .yml (serverless) via Python
# Clean-up after ourselves
#RUN curl --silent --location https://rpm.nodesource.com/setup_8.x | bash - && \
RUN apt-get update &&\ 
    apt-get upgrade -y &&\
    apt-get install -y \
        apt-utils \
        python3-pip python3-dev \
        python3-yaml \
        make \
        nodejs npm \
        vim findutils 
        git && \
     apt-get clean all && rm -rf /var/cache/apt

# Install the serverless framework globally
RUN npm install -g serverless

# Install/upgrade pip, awscli, mysqlclient for both Python 2.7 and Python 3.6
RUN ls -la /usr/local/bin
RUN find / -iname "pip*"

RUN pip-3 install --no-cache-dir --upgrade pip awscli mysqlclient pyyaml
  
ENTRYPOINT ["/bin/bash"] 
# "-c"]

Last stage in dockerfile that creates nginx container with selfsigned cert

#########################################################
FROM docker.io/debian:bullseye-slim
RUN apt-get update && apt-get install -y nginx openssl jo &&\
    rm -rf /var/lib/apt/lists/* &&\
    openssl req -x509 -nodes -days 3650 \
    -subj "/C=NZ/ST=Auckland/O=SelfSigned/OU=private/CN=net.nz" \
    -addext "subjectAltName=DNS:selfsigned.net.nz" \
    -newkey rsa:2048 \
    -keyout /etc/ssl/private/nginx-selfsigned.key \
    -out /etc/ssl/certs/nginx-selfsigned.crt

# link nginx logs to stdout create basic nginx config
RUN ln -sf /dev/stdout /var/log/nginx/access.log &&\
    ln -sf /dev/stderr /var/log/nginx/error.log &&\
    printf '#Generated in Dockerfile;\n\
    charset utf-8;\n\
    server {\n\
    listen 80;\n\
    server_name _;\n\
    return 301 https://$host$request_uri;\n\
    root /var/www/html;\n\
    }\n\
    server {\n\
    listen 443 ssl;\n\
    server_name _;\n\
    root /var/www/html;\n\
    index index.html index.htm;\n\
    ssl_certificate /etc/ssl/certs/nginx-selfsigned.crt;\n\
    ssl_certificate_key /etc/ssl/private/nginx-selfsigned.key;\n\
    # ssl_password_file /usr/nginx/ssl.pass;\n\
    }\n' > /etc/nginx/sites-enabled/default

# add static website to final container
WORKDIR /var/www/html
COPY --from=builder /usr/app/build /var/www/html
EXPOSE 80
EXPOSE 443
COPY Dockerentrypoint.sh /Dockerentrypoint.sh
ENTRYPOINT [ "/Dockerentrypoint.sh" ]
CMD [ "nginx", "-g", "daemon off;" ]

Dockerentrypoint.sh that converts env vars into config file

# Container startups script.
# Allow for runtime configuration through env vars.
# https://12factor.net/build-release-run
set -e
echo "# Start container with $0  PWD=${PWD}"
echo "#"

echo "# cat .version.txt"
cat .version.txt
echo "#"

prefix="REACT_APP_"
echo "# Add env vars ${prefix}* to ''env.js'' at webserver root"
echo "export default () => (`jo -p \`env | grep ${prefix} | sed -e 's/[[:blank:]]/{_!!_}/g'\` end=1`)" | sed -e 's/{_!!_}/ /g' | tee env.js
echo "#"

echo "# Starting docker cmd \$@=$@ ..."
exec "$@"