Give the Kernel Sources section of the Porter's Handbook a

section ID so it does not clutter the filesystem when making
local changes to porters-handbook/book.sgml, making the 'clean'
make(1) target actually remove all files.

en_US.ISO8859-1/books/porters-handbook/book.sgml

@@ -9431,7 +9431,7 @@ GROUPS=	pulse pulse-access pulse-rt</programlisting>
 	<filename>ports/GIDs</filename>.</para>
     </sect1>
 
-    <sect1>
+    <sect1 id="requiring-kernel-sources">
       <title>Ports That Rely on Kernel Sources</title>
 
       <para>Some ports (such as kernel loadable modules) need the