diff --git a/pkgs/build-support/vm/default.nix b/pkgs/build-support/vm/default.nix
index aaeeef12a69d..d3487be717ca 100644
--- a/pkgs/build-support/vm/default.nix
+++ b/pkgs/build-support/vm/default.nix
@@ -127,7 +127,7 @@ rec {
     if test -z "$mountDisk"; then
       mount -t tmpfs none /fs
     else
-      mount -t ext2 /dev/${hd} /fs
+      mount /dev/${hd} /fs
     fi
 
     mkdir -p /fs/dev
@@ -166,7 +166,6 @@ rec {
     halt -d -p -f
   '';
 
-  
   initrd = makeInitrd {
     contents = [
       { object = stage1Init;
@@ -303,7 +302,7 @@ rec {
   '';
 
 
-  createRootFS = ''
+  defaultCreateRootFS = ''
     mkdir /mnt
     ${e2fsprogs}/sbin/mke2fs -F /dev/${hd}
     ${utillinux}/bin/mount -t ext2 /dev/${hd} /mnt
@@ -486,12 +485,12 @@ rec {
     
   fillDiskWithRPMs =
     { size ? 4096, rpms, name, fullName, preInstall ? "", postInstall ? ""
-    , runScripts ? true
+    , runScripts ? true, createRootFS ? defaultCreateRootFS
     }:
     
     runInLinuxVM (stdenv.mkDerivation {
       inherit name preInstall postInstall rpms;
-
+      memSize = 512;
       preVM = createEmptyImage {inherit size fullName;};
 
       buildCommand = ''
@@ -526,10 +525,10 @@ rec {
         eval "$postInstall"
         
         rm /mnt/.debug
-        
-        ${utillinux}/bin/umount /mnt/nix/store
-        ${utillinux}/bin/umount /mnt/tmp
-        ${utillinux}/bin/umount /mnt
+
+        ${utillinux}/bin/umount /mnt/nix/store 
+        ${utillinux}/bin/umount /mnt/tmp 
+        ${utillinux}/bin/umount /mnt 
       '';
 
       passthru = { inherit fullName; };
@@ -631,7 +630,7 @@ rec {
      strongly connected components.  See deb/deb-closure.nix. */
 
   fillDiskWithDebs =
-    { size ? 4096, debs, name, fullName, postInstall ? null }:
+    { size ? 4096, debs, name, fullName, postInstall ? null, createRootFS ? defaultCreateRootFS }:
     
     runInLinuxVM (stdenv.mkDerivation {
       inherit name postInstall;
@@ -712,12 +711,15 @@ rec {
      `primary.xml.gz' file of a Fedora or openSUSE distribution. */
      
   rpmClosureGenerator =
-    {name, packagesList, urlPrefix, packages, archs ? []}:
-    
+    {name, packagesLists, urlPrefixes, packages, archs ? []}:
+    assert (builtins.length packagesLists) == (builtins.length urlPrefixes) ;
     runCommand "${name}.nix" {buildInputs = [perl perlPackages.XMLSimple]; inherit archs;} ''
-      gunzip < ${packagesList} > ./packages.xml
+      ${lib.concatImapStrings (i: pl: ''
+        gunzip < ${pl} > ./packages_${toString i}.xml
+      '') packagesLists}
       perl -w ${rpm/rpm-closure.pl} \
-        ./packages.xml ${urlPrefix} ${toString packages} > $out
+        ${lib.concatImapStrings (i: pl: "./packages_${toString i}.xml ${pl.snd} " ) (lib.zipLists packagesLists urlPrefixes)} \
+        ${toString packages} > $out
     '';
 
 
@@ -726,15 +728,17 @@ rec {
      names. */
      
   makeImageFromRPMDist =
-    { name, fullName, size ? 4096, urlPrefix, packagesList
+    { name, fullName, size ? 4096
+    , urlPrefix ? "", urlPrefixes ? [urlPrefix]
+    , packagesList ? "", packagesLists ? [packagesList]
     , packages, extraPackages ? []
     , preInstall ? "", postInstall ? "", archs ? ["noarch" "i386"]
-    , runScripts ? true }:
+    , runScripts ? true, createRootFS ? defaultCreateRootFS }:
 
     fillDiskWithRPMs {
-      inherit name fullName size preInstall postInstall runScripts;
+      inherit name fullName size preInstall postInstall runScripts createRootFS;
       rpms = import (rpmClosureGenerator {
-        inherit name packagesList urlPrefix archs;
+        inherit name packagesLists urlPrefixes archs;
         packages = packages ++ extraPackages;
       }) { inherit fetchurl; };
     };
diff --git a/pkgs/build-support/vm/rpm/rpm-closure.pl b/pkgs/build-support/vm/rpm/rpm-closure.pl
index 5f333fdfe80b..5efc162784ac 100644
--- a/pkgs/build-support/vm/rpm/rpm-closure.pl
+++ b/pkgs/build-support/vm/rpm/rpm-closure.pl
@@ -1,34 +1,52 @@
 use strict;
 use XML::Simple;
 
-my $packagesFile = shift @ARGV;
-my $urlPrefix = shift @ARGV;
+my @packagesFiles = ();
+my @urlPrefixes = ();
+
+# rpm-closure.pl (<package-file> <url-prefix>)+ <toplevel-pkg>+
+
+while(-f $ARGV[0]) {
+    my $packagesFile = shift @ARGV;
+    my $urlPrefix = shift @ARGV;
+    push(@packagesFiles, $packagesFile);
+    push(@urlPrefixes, $urlPrefix);
+}
+
 my @toplevelPkgs = @ARGV;
 
 my @archs = split ' ', ($ENV{'archs'} or "");
 
-print STDERR "parsing packages...\n";
-
-my $xml = XMLin($packagesFile, ForceArray => ['package', 'rpm:entry', 'file'], KeyAttr => []) or die;
-
-print STDERR "file contains $xml->{packages} packages\n";
-
-
 my %pkgs;
-foreach my $pkg (@{$xml->{'package'}}) {
-    if (scalar @archs > 0) {
-        my $arch = $pkg->{arch};
-        my $found = 0;
-        foreach my $a (@archs) { $found = 1 if $arch eq $a; }
-        next if !$found;
-    }
-    if (defined $pkgs{$pkg->{name}}) {
-        print STDERR "WARNING: duplicate occurrence of package $pkg->{name}\n";
-        next;
-    }
-    $pkgs{$pkg->{name}} = $pkg;
-}
+for (my $i = 0; $i < scalar(@packagesFiles); $i++) {
+    my $packagesFile = $packagesFiles[$i];
+    print STDERR "parsing packages in $packagesFile...\n";
 
+    my $xml = XMLin($packagesFile, ForceArray => ['package', 'rpm:entry', 'file'], KeyAttr => []) or die;
+
+    print STDERR "$packagesFile contains $xml->{packages} packages\n";
+
+    foreach my $pkg (@{$xml->{'package'}}) {
+        if (scalar @archs > 0) {
+            my $arch = $pkg->{arch};
+            my $found = 0;
+            foreach my $a (@archs) { $found = 1 if $arch eq $a; }
+            next if !$found;
+        }
+        if (defined $pkgs{$pkg->{name}}) {
+            my $earlierPkg = $pkgs{$pkg->{name}};
+            print STDERR "WARNING: duplicate occurrence of package $pkg->{name}\n";
+            if ($earlierPkg->{'time'}->{file} <= $pkg->{'time'}->{file}) {
+                print STDERR "WARNING: replaced package $pkg->{name} with newer one\n";
+                $pkg->{urlPrefix} = $urlPrefixes[$i];
+                $pkgs{$pkg->{name}} = $pkg;
+            }
+            next;
+        }
+        $pkg->{urlPrefix} = $urlPrefixes[$i];
+        $pkgs{$pkg->{name}} = $pkg;
+    }
+}
 
 my %provides;
 foreach my $pkgName (keys %pkgs) {
@@ -104,7 +122,7 @@ print "[\n\n";
 foreach my $pkgName (@needed) {
     my $pkg = $pkgs{$pkgName};
     print "  (fetchurl {\n";
-    print "    url = $urlPrefix/$pkg->{location}->{href};\n";
+    print "    url = $pkg->{urlPrefix}/$pkg->{location}->{href};\n";
     if ($pkg->{checksum}->{type} eq "sha") {
         print "    sha1 = \"$pkg->{checksum}->{content}\";\n";
     } elsif ($pkg->{checksum}->{type} eq "sha256") {