Full instructions are listed on a SteamOS FAQ Valve posted today, but if you're not familiar with installing Linux systems, you might want to hold off on trying to configure your own Steam Machine, given the fact that the system is still in beta.
The FAQ explains that "SteamOS is designed to run Steam and Steam games," however, it elaborates, "SteamOS is based on Debian GNU/Linux and is not compatible with Microsoft Windows games and applications. However, SteamOS will soon support seamlessly streaming your games from your Windows computer; watch this page for more information about the In-Home Streaming Beta."
What do you need to run SteamOS? Here's the hardware list from the FAQ:
- Intel or AMD 64-bit capable processor
- 4GB or more memory
- 500GB or larger disk
- NVIDIA graphics card (AMD and Intel graphics support coming soon)
- UEFI boot support
- USB port for installation
Note: one of the installation methods that Valve details requires a 1TB storage device.
You can grab the SteamOS installation files here or this alternate download location and source for Steam OS is located here. Valve has also cautioned against downloading the files from "non-official, un-announce links." We'll be working on installing the OS ourselves over the weekend, but lets us know your own results if you've brave the process yourself!