diff --git a/installer/grub-menu-builder.sh b/installer/grub-menu-builder.sh
index 5d26cdb4327..72635c36433 100644
--- a/installer/grub-menu-builder.sh
+++ b/installer/grub-menu-builder.sh
@@ -147,4 +147,6 @@ for generation in $(
 done
 
 
-cp $tmp $target
+# Atomically update /boot/grub/menu.lst.  !!! should do an fsync()
+# here on $tmp, especially on ext4.
+mv $tmp $target