Flake Modules #

Flake-parts modules that organize flake outputs.

Structure #

flake-modules/
├── common.nix                # Shared pkgs with overlays
├── formatter.nix             # Alejandra formatter
├── nixos-configurations.nix  # NixOS system configs
├── home-configurations.nix   # Home Manager configs
├── hosts.nix                 # Host configs
└── dev-shells.nix           # Development environments

Modules #

common.nix #

Defines shared pkgs instance with:

• allowUnfree = true
• Niri overlay applied
• Used by all other modules via withSystem

Eliminates duplicate pkgs creation.

formatter.nix #

Enables nix fmt using alejandra:

nix fmt                 # Format all files
nix fmt -- --version    # Check version

nixos-configurations.nix #

Creates nixosConfigurations output for each host:

• Uses shared pkgs via withSystem
• Integrates Home Manager
• Imports from hosts/

home-configurations.nix #

Creates homeConfigurations for standalone Home Manager:

• Uses shared pkgs via withSystem
• Enables home-manager switch --flake .#hostname

dev-shells.nix #

Registers development shells from devShells/:

• python, java, rust
• django, chat, mcp-server, stock-analysis

Key Concepts #

perSystem #

Runs for each system in systems list:

perSystem = {pkgs, system, ...}: {
  devShells.python = pkgs.mkShell { ... };
};

withSystem #

Access perSystem context from flake outputs:

flake.nixosConfigurations = {
  host = withSystem "x86_64-linux" ({pkgs, ...}:
    # pkgs available here
  );
};

flake.* #

Define non-perSystem outputs:

flake.nixosModules.default = { ... };

Architecture #

flake.nix
├── systems = ["x86_64-linux"]
└── imports = [
    ├── common.nix              → pkgs (perSystem)
    ├── formatter.nix           → alejandra (perSystem)
    ├── nixos-configurations.nix → uses pkgs (withSystem)
    ├── home-configurations.nix  → uses pkgs (withSystem)
    └── dev-shells.nix          → shells (perSystem)
    ]

Before/After #

Before: 137 lines in flake.nix, duplicate pkgs in 3 places After: 62 lines in flake.nix, single pkgs definition

Adding a Module #

1. Create flake-modules/mymodule.nix
2. Add to imports in flake.nix
3. Use perSystem for system-specific outputs
4. Use flake.* for system-agnostic outputs