diff --git a/configuration/options.nix b/configuration/options.nix
index 31842627bb50..c8a2f07df01f 100644
--- a/configuration/options.nix
+++ b/configuration/options.nix
@@ -62,6 +62,37 @@
   }
 
 
+  {
+    name = ["boot" "kernelParams"];
+    default = [
+      "selinux=0"
+      "apm=on"
+      "acpi=on"
+      "vga=0x317"
+      "console=tty1"
+      "splash=verbose"
+    ];
+    description = "
+      The kernel parameters.  If you want to add additional
+      parameters, it's best to set
+      <option>boot.extraKernelParams</options>.
+    ";
+  }
+
+
+  {
+    name = ["boot" "extraKernelParams"];
+    default = [
+    ];
+    example = [
+      "debugtrace"
+    ];
+    description = "
+      Additional user-defined kernel parameters.
+    ";
+  }
+
+
   {
     name = ["networking" "useDHCP"];
     default = true;
diff --git a/configuration/system-configuration.nix b/configuration/system-configuration.nix
deleted file mode 100644
index 6e6b6bc6e0f1..000000000000
--- a/configuration/system-configuration.nix
+++ /dev/null
@@ -1,63 +0,0 @@
-let
-
-  configuration = {
-    boot = {
-      autoDetectRootDevice = false;
-      rootDevice = "/dev/hda1";
-      readOnlyRoot = false;
-      grubDevice = "/dev/hda";
-    };
-  };
-
-  # Build boot scripts.
-  bootEnv = import ./boot-environment.nix {
-    stage2Init = ""; # Passed on the command line via Grub.
-    inherit configuration;
-  };
-
-  # Extra kernel command line arguments.
-  extraKernelParams = [
-    "selinux=0"
-    "apm=on"
-    "acpi=on"
-    "vga=0x317"
-    "console=tty1"
-    "splash=verbose"
-  ];
-
-in
-
-with bootEnv;
-  
-rec {
-
-  inherit upstartJobs;
-
-
-  system = pkgs.stdenvNew.mkDerivation {
-    name = "system-configuration";
-    builder = ./system-configuration.sh;
-    switchToConfiguration = ./switch-to-configuration.sh;
-    inherit (pkgs) grub coreutils gnused gnugrep diffutils findutils;
-    grubDevice = "/dev/hda"; # !!!
-    inherit bootStage2;
-    inherit activateConfiguration;
-    inherit grubMenuBuilder;
-    inherit etc;
-    kernel = pkgs.kernel + "/vmlinuz";
-    initrd = initialRamdisk + "/initrd";
-    inherit extraKernelParams;
-    # Most of these are needed by grub-install.
-    path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep pkgs.findutils pkgs.diffutils];
-  };
-
-
-  grubMenuBuilder = pkgs.substituteAll {
-    src = ../installer/grub-menu-builder.sh;
-    isExecutable = true;
-    inherit (pkgs) bash;
-    path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep];
-  };
-
-
-}
diff --git a/configuration/boot-environment.nix b/configuration/system.nix
similarity index 78%
rename from configuration/boot-environment.nix
rename to configuration/system.nix
index 762e20424015..f030717491c3 100644
--- a/configuration/boot-environment.nix
+++ b/configuration/system.nix
@@ -1,5 +1,5 @@
-{ system ? __currentSystem
-, stage2Init
+{ platform ? __currentSystem
+, stage2Init ? ""
 , configuration
 }:
 
@@ -10,15 +10,15 @@ rec {
   config = import ./config.nix pkgs.library configuration;
   
 
-  pkgs = import ../pkgs/top-level/all-packages.nix {inherit system;};
+  pkgs = import ../pkgs/top-level/all-packages.nix {system = platform;};
 
   pkgsDiet = import ../pkgs/top-level/all-packages.nix {
-    inherit system;
+    system = platform;
     bootStdenv = pkgs.useDietLibC pkgs.stdenv;
   };
 
   pkgsStatic = import ../pkgs/top-level/all-packages.nix {
-    inherit system;
+    system = platform;
     bootStdenv = pkgs.makeStaticBinaries pkgs.stdenv;
   };
 
@@ -207,4 +207,40 @@ rec {
     ];
   };
 
+
+  # Script to build the Grub menu containing the current and previous
+  # system configurations.
+  grubMenuBuilder = pkgs.substituteAll {
+    src = ../installer/grub-menu-builder.sh;
+    isExecutable = true;
+    inherit (pkgs) bash;
+    path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep];
+  };
+
+
+  # Putting it all together.  This builds a store object containing
+  # symlinks to the various parts of the built configuration (the
+  # kernel, the Upstart services, the init scripts, etc.) as well as a
+  # script `switch-to-configuration' that activates the configuration
+  # and makes it bootable.
+  system = pkgs.stdenvNew.mkDerivation {
+    name = "system";
+    builder = ./system.sh;
+    switchToConfiguration = ./switch-to-configuration.sh;
+    inherit (pkgs) grub coreutils gnused gnugrep diffutils findutils;
+    grubDevice = config.get ["boot" "grubDevice"];
+    kernelParams =
+      (config.get ["boot" "kernelParams"]) ++
+      (config.get ["boot" "extraKernelParams"]);
+    inherit bootStage2;
+    inherit activateConfiguration;
+    inherit grubMenuBuilder;
+    inherit etc;
+    kernel = pkgs.kernel + "/vmlinuz";
+    initrd = initialRamdisk + "/initrd";
+    # Most of these are needed by grub-install.
+    path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep pkgs.findutils pkgs.diffutils];
+  };
+
+
 }
diff --git a/configuration/system-configuration.sh b/configuration/system.sh
similarity index 80%
rename from configuration/system-configuration.sh
rename to configuration/system.sh
index e1f240e218fd..c358e8705728 100644
--- a/configuration/system-configuration.sh
+++ b/configuration/system.sh
@@ -9,10 +9,10 @@ ln -s $initrd $out/initrd
 ln -s $activateConfiguration $out/activate
 ln -s $etc/etc $out/etc
 
-echo "$extraKernelParams" > $out/kernel-params
+echo "$kernelParams" > $out/kernel-params
 
 cat > $out/menu.lst << GRUBEND
-kernel $kernel init=$bootStage2 $extraKernelParams
+kernel $kernel init=$bootStage2 $kernelParams
 initrd $initrd
 GRUBEND
 
diff --git a/installer/grub-menu-builder.sh b/installer/grub-menu-builder.sh
index cc678212a8c5..06371d4af7e6 100644
--- a/installer/grub-menu-builder.sh
+++ b/installer/grub-menu-builder.sh
@@ -23,6 +23,10 @@ addEntry() {
     name="$1"
     path="$2"
 
+    if ! test -e $path/menu.lst; then
+        return
+    fi
+
     cat >> $tmp << GRUBEND
 title $name
 GRUBEND
diff --git a/instances/examples/basic.nix b/instances/examples/basic.nix
new file mode 100644
index 000000000000..d5357785810d
--- /dev/null
+++ b/instances/examples/basic.nix
@@ -0,0 +1,8 @@
+{
+  boot = {
+    autoDetectRootDevice = false;
+    rootDevice = "/dev/hda1";
+    readOnlyRoot = false;
+    grubDevice = "/dev/hda";
+  };
+}
diff --git a/test.sh b/test.sh
index c50ebe907d13..7411e3955f6c 100755
--- a/test.sh
+++ b/test.sh
@@ -1,4 +1,6 @@
 #! /bin/sh
 set -e
-nix-build configuration/system-configuration.nix -A system -K -k
+nix-build configuration/system.nix \
+    --arg configuration 'import ./instances/example.nix' \
+    -A system -K -k
 ./result/bin/switch-to-configuration test
diff --git a/upgrade.sh b/upgrade.sh
index 961bc1959ef0..1022564d9c1b 100755
--- a/upgrade.sh
+++ b/upgrade.sh
@@ -1,4 +1,6 @@
 #! /bin/sh
 set -e
-nix-env -p /nix/var/nix/profiles/system -f configuration/system-configuration.nix -i -A systemConfiguration
+nix-env -p /nix/var/nix/profiles/system -f configuration/system.nix \
+    --arg configuration 'import ./instances/example.nix' \
+    -i -A system
 /nix/var/nix/profiles/system/bin/switch-to-configuration switch