I was wondering how one would proceed in building a docker image that doesn't depend on someone else's stuff that depends on someone else's stuff again that depends on someone else's stuff again etc etc.
Let's have a look at a few examples and try and trace it back ...
NodeJS: https://hub.docker.com/r/readytalk/nodejs/
This is their Dockerfile:
FROM debian:wheezy
RUN apt-get update -y && apt-get install --no-install-recommends -y -q curl python build-essential git ca-certificates
RUN mkdir /nodejs && curl http://nodejs.org/dist/v0.10.36/node-v0.10.36-linux-x64.tar.gz | tar xvzf - -C /nodejs --strip-components=1
ENV PATH $PATH:/nodejs/bin
Let's go to the official Debian Repo: https://hub.docker.com/_/debian/
FROM scratch
ADD rootfs.tar.xz /
CMD ["/bin/bash"]
Let's try the Java Repo: https://hub.docker.com/_/java/
#
# NOTE: THIS DOCKERFILE IS GENERATED VIA "update.sh"
#
# PLEASE DO NOT EDIT IT DIRECTLY.
#
FROM alpine:3.3
# A few problems with compiling Java from source:
# 1. Oracle. Licensing prevents us from redistributing the official JDK.
# 2. Compiling OpenJDK also requires the JDK to be installed, and it gets
# really hairy.
# Default to UTF-8 file.encoding
ENV LANG C.UTF-8
# add a simple script that can auto-detect the appropriate JAVA_HOME value
# based on whether the JDK or only the JRE is installed
RUN { \
echo '#!/bin/sh'; \
echo 'set -e'; \
echo; \
echo 'dirname "$(dirname "$(readlink -f "$(which javac || which java)")")"'; \
} > /usr/local/bin/docker-java-home \
&& chmod +x /usr/local/bin/docker-java-home
ENV JAVA_HOME /usr/lib/jvm/java-1.8-openjdk/jre
ENV PATH $PATH:$JAVA_HOME/bin
ENV JAVA_VERSION 8u72
ENV JAVA_ALPINE_VERSION 8.72.15-r2
RUN set -x \
&& apk add --no-cache \
openjdk8-jre="$JAVA_ALPINE_VERSION" \
&& [ "$JAVA_HOME" = "$(docker-java-home)" ]
Let's check out alpine: https://hub.docker.com/_/alpine/
FROM scratch
ADD rootfs.tar.gz /
So it seems you can build your own Docker image from scratch simply by using the FROM scratch entry.
Looking at the scratch repo, it is confirmed: https://hub.docker.com/_/scratch/
FROM scratch This image is most useful in the context of building base images (such as debian and busybox) or super minimal images (that contain only a single binary and whatever it requires, such as hello-world).
As of Docker 1.5.0 (specifically, docker/docker#8827), FROM scratch is a no-op in the Dockerfile, and will not create an extra layer in your image (so a previously 2-layer image will be a 1-layer image instead).
So in short, scratch creates a blank docker container, then you can copy the stuff in that you need and proceed from there to build your own image from scratch.