nvdnkpr / boot2docker

Lightweight Linux for Docker

boot2docker

boot2docker is a lightweight Linux distribution based on Tiny Core Linux made specifically to run Docker containers. It runs completely from RAM, weighs ~38MB and boots in ~5-6s (YMMV).

It was made during the Global Docker Hack Day on Dec. 3, 2013.

Download

Head over to the Releases Page to grab the ISO.

How to use

Simply boot from the ISO, and you're done. It runs on VMs and bare-metal machines.

If you want your containers to persist accross reboots, just attach an ext4 formatted disk to your VM, and boot2docker will automount it on /var/lib/docker. It will also persist the SSH keys of the machine.

boot2docker auto logs in, but if you want to SSH into the machine, the credentials are:

login: docker
pass: tcuser

Demo

http://www.youtube.com/watch?v=QzfddDvNVv0

Features

• Kernel 3.12.1 with AUFS
• Docker 0.7
• LXC 1.0-alpha2
• Container persistance via disk automount on /var/lib/docker
• SSH keys persistance via disk automount

How to build

boot2docker is built with Docker, via Dockerfiles.

It is composed in three disctinct steps:

• base: fetches, patches with AUFS support and builds the 3.12.1 Linux Kernel with Tiny Core base configuration
• rootfs: builds the base rootfs for boot2docker (not complete)
• running rootfs: when you run this image, it will build the rootfs, download the latest Docker release and create the .iso file on / of the container. This way you can update Docker without having to completely rebuild everything.

So the build process goes like this:

$ sudo docker build -t boot2docker-base base/
$ sudo docker build -t boot2docker rootfs/

Once that's done, to build a custom boot2docker.iso, just run the built rootfs image:

$ sudo docker run --privileged boot2docker
<CONTAINER_ID>
$ sudo docker cp <CONTAINER_ID>:/boot2docker.iso .

FAQ

Why not CoreOS?

I got asked that question a lot, so I thought I should put it here once and for all. I liked the original idea of CoreOS: the smallest possible way to boot to docker. Unfortunately CoreOS has been growing larger and just did too many things for me. I just wanted the fastest way to boot to Docker.