<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-importing-modules">
  <title>Importing Modules</title>
  <para>
    Sometimes NixOS modules need to be used in configuration but exist
    outside of Nixpkgs. These modules can be imported:
  </para>
  <programlisting language="bash">
{ config, lib, pkgs, ... }:

{
  imports =
    [ # Use a locally-available module definition in
      # ./example-module/default.nix
        ./example-module
    ];

  services.exampleModule.enable = true;
}
</programlisting>
  <para>
    The environment variable <literal>NIXOS_EXTRA_MODULE_PATH</literal>
    is an absolute path to a NixOS module that is included alongside the
    Nixpkgs NixOS modules. Like any NixOS module, this module can import
    additional modules:
  </para>
  <programlisting language="bash">
# ./module-list/default.nix
[
  ./example-module1
  ./example-module2
]
</programlisting>
  <programlisting language="bash">
# ./extra-module/default.nix
{ imports = import ./module-list.nix; }
</programlisting>
  <programlisting language="bash">
# NIXOS_EXTRA_MODULE_PATH=/absolute/path/to/extra-module
{ config, lib, pkgs, ... }:

{
  # No `imports` needed

  services.exampleModule1.enable = true;
}
</programlisting>
</section>
