Disable various services when running inside a container

nixos/modules/system/boot/shutdown.nix

@@ -6,20 +6,20 @@ with pkgs.lib;
 
   # This unit saves the value of the system clock to the hardware
   # clock on shutdown.
-  systemd.units."save-hwclock.service" =
-    { wantedBy = [ "shutdown.target" ];
+  systemd.services.save-hwclock =
+    { description = "Save Hardware Clock";
 
-      text =
-        ''
-          [Unit]
-          Description=Save Hardware Clock
-          DefaultDependencies=no
-          Before=shutdown.target
+      wantedBy = [ "shutdown.target" ];
 
-          [Service]
-          Type=oneshot
-          ExecStart=${pkgs.utillinux}/sbin/hwclock --systohc ${if config.time.hardwareClockInLocalTime then "--localtime" else "--utc"}
-        '';
+      unitConfig = {
+        DefaultDependencies = false;
+        ConditionVirtualization = "!systemd-nspawn";
+      };
+
+      serviceConfig = {
+        Type = "oneshot";
+        ExecStart = "${pkgs.utillinux}/sbin/hwclock --systohc ${if config.time.hardwareClockInLocalTime then "--localtime" else "--utc"}";
+      };
     };
 
   boot.kernel.sysctl."kernel.poweroff_cmd" = "${config.systemd.package}/sbin/poweroff";