home-manager/docs/manual/nix-flakes/nixos.md

NixOS module

To use Home Manager as a NixOS module, a bare-minimum flake.nix would be as follows:

{
  description = "NixOS configuration";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    home-manager.url = "github:nix-community/home-manager";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = inputs@{ nixpkgs, home-manager, ... }: {
    nixosConfigurations = {
      hostname = nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";
        modules = [
          ./configuration.nix
          home-manager.nixosModules.home-manager
          {
            home-manager.useGlobalPkgs = true;
            home-manager.useUserPackages = true;
            home-manager.users.jdoe = import ./home.nix;

            # Optionally, use home-manager.extraSpecialArgs to pass
            # arguments to home.nix
          }
        ];
      };
    };
  };
}

The Home Manager configuration is then part of the NixOS configuration and is automatically rebuilt with the system when using the appropriate command for the system, such as nixos-rebuild switch --flake <flake-uri>.

You can use the above flake.nix as a template in /etc/nixos by

$ nix flake new /etc/nixos -t github:nix-community/home-manager#nixos