os/doc/start/iso.md

Installation Media

This project leverages nix-community/nixos-generators for building machine images. In most cases, you'll probably want to use the install-iso format.

Making an installable ISO for hosts/bootstrap.nix is as simple as:

nix run github:nix-community/nixos-generators -- \
  --format install-iso \
  --flake '.#bootstrap'

Then "burn" the ISO to your USB stick (or CD-R if you like!) following the instructions in the NixOS manual (or using your preferred USB burner).

You can also swap out the --format for any of the others supported by nixos-generators.

Continue by following the usual installation instructions in the NixOS manual.

ISO Nix Store and Cache

The ISO image holds the Nix store for the live environment and also acts as a binary cache to the installer. To considerably speed things up, the image already includes all flake inputs as well as the devshell closures.

While you could provision any NixOS machine with the same USB stick, an ISO custom-made for your target host will maximise those local cache hits. For hosts that don't differ too much, a single USB stick might be ok, whereas when there are bigger differences, a custom-made USB stick will be considerably faster.