# Buildroot

> The tool Home Assistant OS is built with. It builds a complete, small Linux system from source, instead of starting from a distribution like Ubuntu.

Source: https://contributors.home-assistant.io/glossary/buildroot/

- In code: `buildroot/`, `buildroot-external/`

The home-assistant/operating-system repository has [Buildroot](https://buildroot.org/) as a Git submodule, and keeps everything specific to Home Assistant OS, like the board configurations and packages, in [`buildroot-external/`](https://github.com/home-assistant/operating-system/tree/dev/buildroot-external). See [Build Home Assistant OS](https://contributors.home-assistant.io/os/operating-system/build/).

## Related terms

- [Home Assistant OS](https://contributors.home-assistant.io/glossary/home-assistant-os/): The operating system made to run Home Assistant, with the Supervisor, apps, and backups. The recommended way to install Home Assistant.
- [RAUC](https://contributors.home-assistant.io/glossary/rauc/): The update system of Home Assistant OS. It installs a new version of the whole system next to the running one, so a device can go back when an update does not work.