Docker sounds very interesting, but I have a ton of questions. I'm very familiar with Chef and Vagrant, and passingly familiar with FreeBSD jails, but I'm havin

Docker sounds very interesting, but I have a ton of questions. I'm very familiar with Chef and Vagrant, and passingly familiar with FreeBSD jails, but I'm having trouble wrapping my head around Docker. Here are some questions: - Why use ENTRYPOINT rather than init.d scripts? - When I'm building the Dockerfile, how do I do something like `vi /etc/apache2/sites-available/my-app`? In other words, how do I drop a whole config file onto the image, the way I'd use Chef files/templates? - Is it possible to parameterize a Dockerfile, so people can use my image but adjust the nginx timeout time? - Do Dockerfile commands need to be idempotent? For example will this cause problems?: `RUN echo "deb http://archive.ubuntu.com/ubuntu http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list` - If I'm using docker to host Rails-on-unicorn, do I still use Capistrano to push a new deploy, or do I spin down the whole docker container then launch another with my latest code? If the latter, are there any existing tools for that?