Merge pull request #49462 from roberth/pkgs-nixos-example

pkgs.nixos: Add example to inline documentation

1 files changed, 50 insertions, 32 deletions

diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 03aab60f40d2..3cd0cc4887a8 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -22109,38 +22109,56 @@ with pkgs;
 
   nixops-dns = callPackage ../tools/package-management/nixops/nixops-dns.nix { };
 
-  /*
-   * Evaluate a NixOS configuration using this evaluation of Nixpkgs.
-   *
-   * With this function you can write, for example, a package that
-   * depends on a custom virtual machine image.
-   *
-   * Parameter: A module, path or list of those that represent the
-   *            configuration of the NixOS system to be constructed.
-   *
-   * Result:    An attribute set containing packages produced by this
-   *            evaluation of NixOS, such as toplevel, kernel and
-   *            initialRamdisk.
-   *            The result can be extended in the modules by defining
-   *            extra options in system.build.
-   *
-   * Unlike in plain NixOS, the nixpkgs.config, nixpkgs.overlays and
-   * nixpkgs.system options will be ignored by default. Instead,
-   * nixpkgs.pkgs will have the default value of pkgs as it was
-   * constructed right after invoking the nixpkgs function (e.g. the
-   * value of import <nixpkgs> { overlays = [./my-overlay.nix]; }
-   * but not the value of (import <nixpkgs> {} // { extra = ...; }).
-   *
-   * If you do want to use the config.nixpkgs options, you are
-   * probably better off by calling nixos/lib/eval-config.nix
-   * directly, even though it is possible to set config.nixpkgs.pkgs.
-   *
-   * For more information about writing NixOS modules, see
-   * https://nixos.org/nixos/manual/index.html#sec-writing-modules
-   *
-   * Note that you will need to have called Nixpkgs with the system
-   * parameter set to the right value for your deployment target.
-   */
+  /* Evaluate a NixOS configuration using this evaluation of Nixpkgs.
+
+     With this function you can write, for example, a package that
+     depends on a custom virtual machine image.
+
+     Parameter: A module, path or list of those that represent the
+                configuration of the NixOS system to be constructed.
+
+     Result:    An attribute set containing packages produced by this
+                evaluation of NixOS, such as toplevel, kernel and
+                initialRamdisk.
+                The result can be extended in the modules by defining
+                extra attributes in system.build.
+
+     Example:
+
+         let
+           myOS = pkgs.nixos ({ lib, pkgs, config, ... }: {
+
+             config.services.nginx = {
+               enable = true;
+               # ...
+             };
+
+             # Use config.system.build to exports relevant parts of a
+             # configuration. The runner attribute should not be
+             # considered a fully general replacement for systemd
+             # functionality.
+             config.system.build.run-nginx = config.systemd.services.nginx.runner;
+           });
+         in
+           myOS.run-nginx
+
+     Unlike in plain NixOS, the nixpkgs.config, nixpkgs.overlays and
+     nixpkgs.system options will be ignored by default. Instead,
+     nixpkgs.pkgs will have the default value of pkgs as it was
+     constructed right after invoking the nixpkgs function (e.g. the
+     value of import <nixpkgs> { overlays = [./my-overlay.nix]; }
+     but not the value of (import <nixpkgs> {} // { extra = ...; }).
+
+     If you do want to use the config.nixpkgs options, you are
+     probably better off by calling nixos/lib/eval-config.nix
+     directly, even though it is possible to set config.nixpkgs.pkgs.
+
+     For more information about writing NixOS modules, see
+     https://nixos.org/nixos/manual/index.html#sec-writing-modules
+
+     Note that you will need to have called Nixpkgs with the system
+     parameter set to the right value for your deployment target.
+  */
   nixos = configuration:
     (import (self.path + "/nixos/lib/eval-config.nix") {
       inherit (pkgs.stdenv.hostPlatform) system;