Switch to using nslookup, which should come with nsupdate.

update_ip.sh

@@ -7,7 +7,8 @@ host=desktop
 secret=""
 
 ip=$(wget -4 -q -O - http://treehouse.org.za/ip)
-set_ip=$(dig +short ${host}.${zone})
+#set_ip=$(dig +short -t a ${host}.${zone})
+set_ip=$(nslookup -type=a ${host}.${zone} | awk '/^Address: / { print $2 }')
 
 if [ -z ${ip} ] || [ -z ${cache} ]; then
 	exit;