Index: trunk/tools/diskspace/nebulous_data.pl
===================================================================
--- trunk/tools/diskspace/nebulous_data.pl	(revision 32624)
+++ trunk/tools/diskspace/nebulous_data.pl	(revision 32625)
@@ -63,5 +63,5 @@
 my $total_volume = 0;
 my $used_volume  = 0;
-open(DF,"df -B 1 /data/${neb}/ |") || die "Cannot run df\n";
+open(DF,"df -B 1 /export/${neb}/ |") || die "Cannot run df\n";
 while(<DF>) {
     chomp;
@@ -113,7 +113,8 @@
     }
 }
-my $external_volume = $used_volume - $total_volume;
-print $out_fh "EXTERNAL UNKNOWN 1 $external_volume\n";
-
+if ($used_volume > 0) {
+    my $external_volume = $used_volume - $total_volume;
+    print $out_fh "EXTERNAL UNKNOWN 1 $external_volume\n";
+}
 close($out_fh);