diff --git a/pkgs/build-support/vm/vm.nix b/pkgs/build-support/vm/default.nix
similarity index 97%
rename from pkgs/build-support/vm/vm.nix
rename to pkgs/build-support/vm/default.nix
index 13b9ed5ea756..7d334f045409 100644
--- a/pkgs/build-support/vm/vm.nix
+++ b/pkgs/build-support/vm/default.nix
@@ -1,4 +1,6 @@
-with import ../../.. {};
+{pkgs}:
+
+with pkgs;
 
 rec {
 
@@ -279,8 +281,11 @@ rec {
     postHook = ''
       PATH=/usr/bin:/bin:/usr/sbin:/sbin
       SHELL=/bin/sh
+      eval "$origPostHook"
     '';
 
+    origPostHook = if attrs ? postHook then attrs.postHook else "";
+
     /* Don't run Nix-specific build steps like patchelf. */
     fixupPhase = "true";
   });
@@ -354,8 +359,14 @@ rec {
      tarball must contain an RPM specfile. */
   
   buildRPM = attrs: runInLinuxImage (stdenv.mkDerivation (attrs // {
-    phases = "buildPhase installPhase";
+    phases = "sysInfoPhase buildPhase installPhase";
   
+    sysInfoPhase = ''
+      header "base RPMs"
+      rpm -qa --qf "%{Name}-%{Version}-%{Release} (%{Arch}; %{Distribution}; %{Vendor})\n"
+      stopNest
+    '';
+    
     buildPhase = ''
       # Hacky: RPM looks for <basename>.spec inside the tarball, so
       # strip off the hash.
diff --git a/pkgs/build-support/vm/test.nix b/pkgs/build-support/vm/test.nix
index e25704612dcc..6c25667a222b 100644
--- a/pkgs/build-support/vm/test.nix
+++ b/pkgs/build-support/vm/test.nix
@@ -1,5 +1,5 @@
 with import ../../.. {};
-with import ./vm.nix;
+with vmTools;
 
 rec {
 
@@ -50,6 +50,10 @@ rec {
     src = nixUnstable.src;
     diskImage = debianImage;
     memSize = 512;
+    phases = "sysInfoPhase unpackPhase patchPhase configurePhase buildPhase checkPhase installPhase fixupPhase distPhase";
+    sysInfoPhase = ''
+      dpkg-query --list
+    '';
   });
   
 
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index decc0d0825cd..b10191f17c45 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -29,7 +29,7 @@
 }:
 
 
-rec {
+let pkgs = rec {
 
 
   ### Symbolic names.
@@ -392,6 +392,10 @@ rec {
   nukeReferences = import ../build-support/nuke-references/default.nix {
     inherit stdenv;
   };
+
+  vmTools = import ../build-support/vm/default.nix {
+    inherit pkgs;
+  };
   
 
   ### TOOLS
@@ -6160,4 +6164,4 @@ rec {
 
   #my_env = import ../misc/my_env;
 
-}
+}; in pkgs