diff --git a/modules/installer/cd-dvd/iso-image.nix b/modules/installer/cd-dvd/iso-image.nix
index 64f788993fe6..49d1e5e24a3e 100644
--- a/modules/installer/cd-dvd/iso-image.nix
+++ b/modules/installer/cd-dvd/iso-image.nix
@@ -85,4 +85,12 @@ in
         }
       ];
   };
+
+  # After booting, register the contents of the Nix store on the CD in
+  # the Nix database in the tmpfs.
+  boot.postBootCommands =
+    ''
+      ${config.environment.nix}/bin/nix-store --load-db < /nix-path-registration
+      rm /nix-path-registration
+    '';
 }
diff --git a/modules/system/boot/stage-2-init.sh b/modules/system/boot/stage-2-init.sh
index 121cf46e12a4..f8cd3e913c30 100644
--- a/modules/system/boot/stage-2-init.sh
+++ b/modules/system/boot/stage-2-init.sh
@@ -131,7 +131,7 @@ export MODULE_DIR=@kernel@/lib/modules/
 
 
 # Run any user-specified commands.
-@shell@ @bootLocal@
+@shell@ @postBootCommands@
 
 
 # Start Upstart's init.  We start it through the
diff --git a/modules/system/boot/stage-2.nix b/modules/system/boot/stage-2.nix
index f0e90452ebe5..440ff70965f2 100644
--- a/modules/system/boot/stage-2.nix
+++ b/modules/system/boot/stage-2.nix
@@ -4,12 +4,13 @@ let
 
   options = {
 
-    boot.localCommands = pkgs.lib.mkOption {
+    boot.postBootCommands = pkgs.lib.mkOption {
       default = "";
-      example = "text=anything; echo You can put $text here.";
-      description = "
+      example = "rm -f /var/log/messages";
+      merge = pkgs.lib.mergeStringOption;
+      description = ''
         Shell commands to be executed just before Upstart is started.
-      ";
+      '';
     };
 
   };
@@ -19,28 +20,27 @@ let
   activateConfiguration = config.system.activationScripts.script;
 
   # Path for Upstart jobs.  Should be quite minimal.
-  upstartPath = [
-    pkgs.coreutils
-    pkgs.findutils
-    pkgs.gnugrep
-    pkgs.gnused
-    pkgs.upstart
-  ];
-
-  bootLocal = config.boot.localCommands;
+  upstartPath =
+    [ pkgs.coreutils
+      pkgs.findutils
+      pkgs.gnugrep
+      pkgs.gnused
+      pkgs.upstart
+    ];
 
   bootStage2 = substituteAll {
     src = ./stage-2-init.sh;
     isExecutable = true;
     inherit kernel upstart activateConfiguration upstartPath;
-    path = [
-      coreutils
-      utillinux
-      udev
-      upstart
-    ];
-    bootLocal = writeText "local-cmds" bootLocal;
+    path =
+      [ coreutils
+        utillinux
+        udev
+        upstart
+      ];
+    postBootCommands = writeText "local-cmds" config.boot.postBootCommands;
   };
+  
 in
 
 {