fix typo: up --> yp

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@1770 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

appendixa/nettools-desc.xml

@@ -58,7 +58,7 @@ routing table.</para></sect4>
 normal terminal line into one of several "network" modes.</para></sect4>
 
 <sect4><title>ypdomainname</title>
-<para>updomainname shows or sets the system's NIS/YP domain
+<para>ypdomainname shows or sets the system's NIS/YP domain
 name.</para></sect4>
 
 </sect3>