Boot2Docker (modernized)

Boot2Docker — no longer deprecated — this is a modernized revival of the lightweight Linux distribution made to run Docker containers. It now focuses on:

• Updated Linux Kernel with Tiny Core Linux 16.x
• Full cgroup v2 support
• Compatibility with FreeBSD, including support for VirtualBox and bhyve
• Removal of outdated or unmaintained VM backends

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Overview

Boot2Docker is a minimal Linux distribution that runs Docker containers out of the box. It runs entirely from RAM, boots in seconds, and is ideal for lightweight or temporary container environments.

Features

• ⚙️ Modern (6.12) Linux kernel (aligned with Docker compatibility)
• 🐧 Based on Tiny Core Linux 16.x
• 🧠 Runs from RAM (~75MB ISO)
• 📦 Docker preinstalled
• 📂 Persistent storage via disk automount
• 🔐 SSH key and Docker data persistence
• 🧠 cgroup v2 support (for modern container runtimes)
• 🧊 Focus on FreeBSD: VirtualBox and bhyve VM drivers supported

This project emphasizes support for FreeBSD users by maintaining clean, minimal integration with bhyve and VirtualBox. Other VM drivers and Docker Toolbox are no longer supported.

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Installation

ISO download

Releases are published here:
👉 GitHub Releases

Usage with Docker Machine

You can use the ISO with Docker Machine and a compatible driver:

docker-machine create \
  --driver virtualbox \
  --virtualbox-boot2docker-url=https://github.com/atagtm/boot2docker/releases/download/v28.3.2/boot2docker.iso \
  default

For FreeBSD, use a bhyve-compatible driver like docker-machine-driver-bhyve (updating is in progress).

Configuration and Debugging

Customizing Docker daemon

You can configure the Docker daemon by editing. For example, to enable core dumps:

# vi /var/lib/boot2docker/profile
EXTRA_ARGS="--default-ulimit core=-1"

or to enable containerd image store:

# vi /etc/docker/daemon.json
{
  "features": {
    "containerd-snapshotter": true
  }
}

Then restart the VM or the daemon.

SSH into VM

$ docker-machine ssh default

Docker Machine auto logs in using the generated SSH key, but if you want to SSH into the machine manually (or you're not using a Docker Machine managed VM), the credentials are:

user: docker
pass: tcuser

Persist data

Boot2docker uses Tiny Core Linux, which runs from RAM and so does not persist filesystem changes by default.

When you run docker-machine, the tool auto-creates a disk that will be automounted and used to persist your docker data in /var/lib/docker and /var/lib/boot2docker. This virtual disk will be removed when you run docker-machine delete default. It will also persist the SSH keys of the machine. Changes outside of these directories will be lost after powering down or restarting the VM.

If you are not using the Docker Machine management tool, you can create an ext4 formatted partition with the label boot2docker-data (mkfs.ext4 -L boot2docker-data /dev/sdX5) to your VM or host, and Boot2Docker will automount it on /mnt/sdX and then softlink /mnt/sdX/var/lib/docker to /var/lib/docker.

Contributing

This is a community-driven continuation of the original Boot2Docker project. Patches welcome — especially if you're improving support for FreeBSD or helping slim the image even more.

License

MIT / Apache 2.0 Originally by the Docker team; continued by community.