This is my experimental area.
For example,
FROM ubuntu:14.04
MAINTAINER KOYAMA Youichi <koyama41@gmail.com>
WORKDIR /
RUN apt-get update && apt-get -y upgrade
RUN apt-get -y install unbound
(from ubuntu14.04-unbound/Dockerfile)
if you'd like to build the docker image above, try:
% git clone https://github.com/koyama41/dockerfiles.git
% cd dockerfiles
% cd ubuntu14.04-unbound
% docker build .