dockerfile

FROM base:container 
USER root # the user which the container runs
COPY ./host/file /container/file
ENV myenvironment=admin\
    myenv2=password
 
RUN commands to be executed # eg. apt install software
USER myuser # switch back to user with less permission
 
ENTRYPOINT ["./entrypoint.sh"] # what the command container should run when starting the container

FROM the base container
ENV define environmental variables

• the env variable would be visible in the container by env function
  RUN execute Linux commands in the container
• split RUN commands to multiple lines
• run apt update && apt install in the same RUN command
• remove the apt cache afterward

    && rm -rf /var/lib/apt/lists/*
    && apt clean # officla ubuntu Docker image does this automatically

COPY copy file from host directory to container
CMD translate to entry point that runs after container starts, the CMD argument has to be in double quotes.
ENTRYPOINT is what the container will run as when exec

• by default, the entrypoint is /bin/sh -c so with docker exec container python app.py the command run in the container will be /bin/sh -c python app.py
• when entrypoint is set as python then executing the same command adobe will not work and for the same as above the exec command is now docker exec container app.py

Multi-arch Build

docker buildx build --platform linux/arm64 . -t caddytest

• using docker buildx, we can build an image that is compatible with many architectures

Multi-stage Build