diff --git a/src/pylorax/__init__.py b/src/pylorax/__init__.py
index b3b06a33..ddd047ae 100644
--- a/src/pylorax/__init__.py
+++ b/src/pylorax/__init__.py
@@ -189,7 +189,8 @@ class Lorax(BaseLoraxClass):
         buildstamp.write(joinpaths(self.inroot, ".buildstamp"))
 
         if self.debug:
-            rb.writepkglists(joinpaths(self.workdir, "pkglists"))
+            rb.writepkglists(joinpaths(logdir, "pkglists"))
+            rb.writepkgsizes(joinpaths(logdir, "original-pkgsizes.txt"))
 
         logger.info("doing post-install configuration")
         rb.postinstall()
@@ -208,6 +209,9 @@ class Lorax(BaseLoraxClass):
         logger.info("cleaning unneeded files")
         rb.cleanup()
 
+        if self.debug:
+            rb.writepkgsizes(joinpaths(logdir, "final-pkgsizes.txt"))
+
         logger.info("creating the runtime image")
         runtime = "images/install.img"
         compression = self.conf.get("compression", "type")
diff --git a/src/pylorax/treebuilder.py b/src/pylorax/treebuilder.py
index 844d1de1..11491d0a 100644
--- a/src/pylorax/treebuilder.py
+++ b/src/pylorax/treebuilder.py
@@ -110,6 +110,14 @@ class RuntimeBuilder(object):
         removelocales = locales.difference(keeplocales)
         self._runner.run("runtime-cleanup.tmpl", removelocales=removelocales)
 
+    def writepkgsizes(self, pkgsizefile):
+        '''debugging data: write a big list of pkg sizes'''
+        fobj = open(pkgsizefile, "w")
+        getsize = lambda f: os.lstat(f).st_size if os.path.exists(f) else 0
+        for p in sorted(self.yum.doPackageLists(pkgnarrow='installed').installed):
+            pkgsize = sum(getsize(joinpaths(self.vars.root,f)) for f in p.filelist)
+            fobj.write("{0.name}.{0.arch}: {1}\n".format(p, pkgsize))
+
     def generate_module_data(self):
         root = self.vars.root
         moddir = joinpaths(root, "lib/modules/")