A basic Dockerfile
Lets write ourselves a generic Dockerfile using build-args to update an image for apt based distros
ARG DISTRO=ubuntu
ARG BASEIMAGE=xenial
FROM ${DISTRO}:${BASEIMAGE}
# This DockerFile is looked after by
LABEL maintainer "James Percival <me@example.com>"
# Update the system
RUN apt update && apt -y dist-upgrade
You can then build images with e.g.
docker build -t debian-stable --build-arg DISTRO=debian --build-arg BASEIMAGE=stable Dockerfile
and then fire up a root session with
docker run --rm --it debian-stable bash