Imports

The imports list tells the module system which other modules to include. All imported modules are merged together as if they had been written in a single file. Imports are the primary mechanism for composing a NixOS configuration from reusable pieces.

Basic imports

{ ... }:

{
  imports = [
    ./hardware-configuration.nix
    ./networking.nix
    ./users.nix
  ];
}

Paths in imports can be:

• Relative paths — resolved relative to the file containing the imports list
• Absolute paths — used as-is
• Module values — a Nix expression that evaluates to a module (a function or attribute set); used when importing from flake inputs or nixpkgs

Importing from nixpkgs

NixOS modules from nixpkgs are imported automatically and do not need to be listed. For third-party modules shipped as a nixpkgs overlay or a separate path:

imports = [
  "${inputs.some-flake}/modules/mymodule.nix"
];

Importing inline modules

An element of imports can be a module value directly, not just a path:

imports = [
  # Inline module — useful for small conditional inclusions
  ({ lib, ... }: {
    networking.firewall.enable = lib.mkDefault true;
  })
];

Conditional imports

The module system evaluates imports before options, so you cannot use config values, and by extension pkgs, to decide what to import — the import list must be statically known. For conditional behaviour, use mkIf inside the imported module rather than importing conditionally.

If you genuinely need to select between two modules based on some value, encode the condition in a Nix if expression using only values available before evaluation:

{ config, ... }:

{
  imports = [
    # Fails with infinite recursion. `pkgs` derives from `config.nixpkgs.pkgs` which creates
    # a strong cycle between imports and config
    (if pkgs.stdenv.isLinux then ./linux.nix else ./darwin.nix)
  ];

  # Better alternative, config can alter other config values
  config.programs.steam.enable = pkgs.stdenv.hostPlatform.isLinux;
}

If you truly want conditional imports, you must use specialArgs when evaluating the NixOS modules:

# flake.nix
nixosConfigurations.work = nixpkgs.lib.nixosSystem rec {
  system = "x86_64-linux";
  specialArgs = { isLocal = true; };
  modules = [
    ./configuration.nix
  ];
};

# In any module
{ config, lib, pkgs, isLocal, ... }:

{
  imports = if isLocal then [
    ./local-profile.nix
  ] else [
    ./remote-profile.nix
  ];
}

specialArgs can be thought of as defined before any module logic. Thus they exist outside of the fixed point resolution for config, options, or pkgs.

Note: Often it is easier to just do all imports at the top-level, instead of branching logic in modules

# Alternative to do decision making at the module level, you can do it as the system level as well.
nixosConfigurations.work = nixpkgs.lib.nixosSystem rec {
  system = "x86_64-linux";
  modules = [
    ./shared-configuration.nix
    ./local-profile.nix
  ];
};

nixosConfigurations.remote = nixpkgs.lib.nixosSystem rec {
  system = "x86_64-linux";
  modules = [
    ./shared-configuration.nix
    ./remote-profile.nix
  ];
};

Import order and duplicates

The module system deduplicates imports: if the same file or module value is imported more than once (from different places in the tree), it is only evaluated once. This means you can safely import a shared module from multiple places without worrying about double-application.

Import order does not affect the final result for most configuration — merging is commutative for the common types. Order only matters for mkOrder, which is covered in the merging chapter.

Structuring a configuration with imports

A common pattern is a top-level configuration.nix that delegates to per-concern files:

/etc/nixos/
├── configuration.nix   # imports everything else
├── hardware-configuration.nix
├── networking.nix
├── users.nix
├── services/
│   ├── nginx.nix
│   └── postgresql.nix
└── profiles/
    └── workstation.nix

# configuration.nix
{ ... }:

{
  imports = [
    ./hardware-configuration.nix
    ./networking.nix
    ./users.nix
    ./services/nginx.nix
    ./services/postgresql.nix
    ./profiles/workstation.nix
  ];
}

Each file focuses on one concern and can be added, removed, or shared between machines independently.

Importing modules from flakes

When using NixOS flakes, modules from external inputs are imported by passing them through nixosSystem:

# flake.nix
{
  inputs.home-manager.url = "github:nix-community/home-manager";

  outputs = { nixpkgs, home-manager, ... }: {
    nixosConfigurations.myhost = nixpkgs.lib.nixosSystem {
      modules = [
        ./configuration.nix
        home-manager.nixosModules.home-manager
      ];
    };
  };
}

The modules argument to nixosSystem is equivalent to a top-level imports list. All modules passed here are merged together with the NixOS module collection.