Home Assistant Operating System (formerly HassOS) is a Linux based operating system optimized to host Home Assistant and its Add-ons.
Home Assistant Operating System uses Docker as its container engine. By default it deploys the Home Assistant Supervisor as a container. Home Assistant Supervisor in turn uses the Docker container engine to control Home Assistant Core and Add-Ons in separate containers. Home Assistant Operating System is not based on a regular Linux distribution like Ubuntu. It is built using Buildroot and it is optimized to run Home Assistant. It targets single board compute (SBC) devices like the Raspberry Pi or ODROID but also supports x86-64 systems with UEFI.
See the full list and specific models here
If you just want to use Home Assistant the official getting started guide and installation instructions take you through how to download Home Assistant Operating System and get it running on your machine.
If you're interested in finding out more about Home Assistant Operating System and how it works read on...
If you don't have experience with embedded systems, Buildroot or the build process for Linux distributions it is recommended to read up on these topics first (e.g. Bootlin has excellent resources).
The Home Assistant Operating System documentation can be found on the Home Assistant Developer Docs website.
The Development build GitHub Action Workflow is a manually triggered workflow which creates Home Assistant OS development builds. The development builds are available at https://os-artifacts.home-assistant.io/index.html.