Add a machine-info module

modules/machine-info.nix

@@ -0,0 +1,119 @@
+{ config, pkgs, lib, ... }@nixpkgs: with lib; {
+	options.environment.machineInfo = mkOption {
+		description = lib.mdDoc ''
+			Machine metadata, including stylized hostname, computer icon, etc.
+
+			This module controls the options written to `/etc/machine-info`.  For more
+			information, see [the freedesktop documentation][1].
+
+			[1]: https://www.freedesktop.org/software/systemd/man/machine-info.html
+		'';
+		default = {};
+		type = types.submodule { options = {
+
+			prettyHostname = mkOption {
+				description = lib.mdDoc ''
+					A pretty, human-readable hostname for this machine, potentially including
+					spaces, unicode, and emoji.  If unset, this falls back to the network hostname
+					set in `networking.hostName`.
+				'';
+				type = with types; nullOr str;
+				default = null;
+				defaultText = literalExpression "null";
+				example = literalExpression "\"Jade's Laptop 💎\"";
+			};
+
+			iconName = mkOption {
+				description = lib.mdDoc ''
+					An XDG icon which should be associated with this machine.  Some common choices
+					include:  `"computer"`, `"phone"`, but a complete list of icons can be found in
+					the [XDG Icon Naming Spec][1].
+
+					If left unset, applications will typically default to `"computer"`.
+
+					[1]: https://specifications.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html
+				'';
+				type = with types; nullOr str;
+				default = null;
+				defaultText = literalExpression "null";
+				example = literalExpression "\"computer\"";
+			};
+
+			chassis = mkOption {
+				description = lib.mdDoc ''
+					The type of chassis this machine resides within.  This is typically detected
+					automatically, but can be manually overridden here.
+				'';
+				type = with types; nullOr (enum [
+					"desktop"
+					"laptop"
+					"convertible"
+					"server"
+					"tablet"
+					"handset"
+					"watch"
+					"embedded"
+					"vm"
+					"container"
+				]);
+				default = null;
+				defaultText = literalExpression "null";
+				example = literalExpression "\"server\"";
+			};
+
+			deployment = mkOption {
+				description = lib.mdDoc ''
+					If this machine is part of a deployment environment / pipeline, this option can
+					be used to specify what environment/pipeline stage it manages.
+
+					Typically, but not necessarily, set to something like `"development"`,
+					`"integration"`, `"staging"`, or `"production"`.
+				'';
+				type = with types; nullOr str;
+				default = null;
+				defaultText = literalExpression "null";
+				example = literalExpression "\"production\"";
+			};
+
+			location = mkOption {
+				description = lib.mdDoc ''
+					A human-readable short description of the location of this machine.
+
+					This can be set to whatever has the most meaning for you, for example "Living
+					Room", "Left Rack, 2nd Shelf", or "Parishville, NY".
+				'';
+				type = with types; nullOr str;
+				default = null;
+				defaultText = literalExpression "null";
+				example = literalExpression "\"Bedroom\"";
+			};
+
+			extraOptions = mkOption {
+				description = lib.mdDoc ''
+				Extra variables to put in `/etc/machine-info`
+				'';
+				type = with types; attrsOf str;
+				default = {};
+				defaultText = literalExpression "{ }";
+				example = literalExpression "{ HARDWARE_VENDOR = \"Intel Corp.\" }";
+			};
+
+		};};
+	};
+
+	config.environment.etc.machine-info =
+		with config.environment.machineInfo;
+		let
+			rawShellVars = {
+				PRETTY_HOSTNAME = prettyHostname;
+				ICON_NAME       = iconName;
+				CHASSIS         = chassis;
+				DEPLOYMENT      = deployment;
+				LOCATION        = location;
+			} // extraOptions;
+			nonNullShellVars = attrsets.filterAttrs (k: v: v != null) rawShellVars;
+		in rec {
+				text = strings.toShellVars nonNullShellVars;
+				enable = builtins.stringLength text > 0;
+			};
+}

nixos.nix

@@ -10,6 +10,7 @@ let systemInformation = import ./system/system-information.nix; in
 		[
 			./configs/filesystems.nix
 			./system/hardware-requirements.nix
+			./modules/machine-info.nix
 			<home-manager/nixos>
 		];
 
@@ -166,9 +167,7 @@ let systemInformation = import ./system/system-information.nix; in
 		};
 	};
 
-	environment.etc.machine-info.text = lib.strings.toShellVars {
-		PRETTY_HOSTNAME = systemInformation.prettyHostname;
-	};
+	environment.machineInfo.prettyHostname = systemInformation.prettyHostname;
 
 	# Enable the OpenSSH daemon.
 	# services.openssh.enable = true;