diff --git a/howto b/howto
index 3e7f4f0fd9d4..13b8aa3b8bf7 100644
--- a/howto
+++ b/howto
@@ -8,7 +8,7 @@ NixOS.
 
 Install Nix. Checkout nixpkgs from Subversion, as well as nixu. Adapt the
 scripts in nixu to reflect the location of nixpkgs (default /nixpkgs).
-Make a directory /tmp/arch. Run ./make-disk.sh. Wait.
+Make sure mktemp is installed. Run ./make-disk.sh. Wait.
 
   Burning
 
diff --git a/make-disk.sh b/make-disk.sh
index f8293d9c38a8..6e87f0e488ff 100755
--- a/make-disk.sh
+++ b/make-disk.sh
@@ -3,7 +3,7 @@
 # deps is an array
 declare -a deps
 
-archivesDir=/tmp/arch
+archivesDir=$(mktemp -d)
 manifest=${archivesDir}/MANIFEST
 nixpkgs=/nixpkgs/trunk/pkgs
 fill_disk=$archivesDir/scripts/fill-disk.sh
@@ -15,13 +15,6 @@ initrd=/tmp/initram.img
 initdir=${archivesDir}/initdir
 initscript=$archivesDir/scripts/init.sh
 
-echo cleaning old build
-
-# keep chmod happy
-touch ${archivesDir}/blah
-chmod -f -R +w ${archivesDir}/*
-rm -rf ${archivesDir}/*
-
 NIX_CMD_PATH=$(dirname $(which nix-store))
 
 storeExpr=$($NIX_CMD_PATH/nix-store -qR $($NIX_CMD_PATH/nix-store -r $(echo '(import ./pkgs.nix).everything' | $NIX_CMD_PATH/nix-instantiate -)))
@@ -250,4 +243,4 @@ mkisofs -rJ -o ${bootiso} -b isolinux/isolinux.bin -c isolinux/boot.cat \
 echo cleaning up
 
 chmod -f -R +w ${archivesDir}/*
-#rm -rf ${archivesDir}/*
+rm -rf ${archivesDir}/*