Configuration Output

import { Aside } from ‘@astrojs/starlight/components’;

Overview

Den transforms den.hosts and den.homes declarations into standard Nix configurations placed on flake.nixosConfigurations, flake.darwinConfigurations, and flake.homeConfigurations.

graph LR
  H["den.hosts"] -->|"osConfiguration"| NC["flake.nixosConfigurations"]
  H -->|"osConfiguration"| DC["flake.darwinConfigurations"]
  HM["den.homes"] -->|"homeConfiguration"| HC["flake.homeConfigurations"]

The Build Process

For each entry in den.hosts and den.homes, Den:

Resolves the main module — applies the context pipeline to produce a single Nix module containing all class-specific configurations
Calls the instantiate function — passes the module to the platform builder
Places the result — puts it at flake.<intoAttr>.<name>

OS Configurations

Each host in den.hosts.<system>.<name> builds via:

host.instantiate {
  modules = [
    host.mainModule
    { nixpkgs.hostPlatform = lib.mkDefault host.system; }
  ];
}

The mainModule is the result of applying den.ctx.host { host } and resolving the aspect tree for the host’s class.

Home Configurations

Each home in den.homes.<system>.<name> builds via:

home.instantiate {
  pkgs = home.pkgs;
  modules = [ home.mainModule ];
}

Where home.pkgs defaults to inputs.nixpkgs.legacyPackages.<system>.

Output Placement

Results are folded into flake by intoAttr:

Class	Default `intoAttr`
`nixos`	`nixosConfigurations`
`darwin`	`darwinConfigurations`
`systemManager`	`systemConfigs`
`homeManager`	`homeConfigurations`

Override intoAttr to place configs elsewhere:

den.hosts.x86_64-linux.my-wsl = {
  intoAttr = "wslConfigurations";
  users.vic = { };
};

Main Module Resolution

The bridge between Den’s schema and final modules is the mainModule, computed internally as:

graph TD
  Entity["host / home definition"]
  Entity -->|"ctx.host / ctx.home"| Intent["Apply context pipeline"]
  Intent -->|"aspect.resolve { class }"| Module["Single Nix module"]
  Module --> Instantiate["instantiate function"]
  Instantiate --> Output["flake.<intoAttr>.<name>"]

The context pipeline collects contributions from:

The entity’s own aspect (host aspect or home aspect)
User aspects (for hosts with users)
den.default includes
Context-specific includes (den.ctx.*.includes)
Batteries and namespace aspects

All contributions for the matching class are merged into one module.

Without Flake-Parts

When inputs.flake-parts is not present, Den provides a minimal options.flake definition so that configuration outputs have a place to be collected. This allows Den to work standalone or with any module evaluation system.