Comment 5 for bug 9471

According to the sudoers manual:

"Beware that turning on fqdn requires sudo to make DNS lookups which may make
sudo unusable if DNS stops working (for example if the machine is not plugged
into the network). Also note that you must use the host's official name as DNS
knows it. That is, you may not use a host alias (CNAME entry) due to performance
issues and the fact that there is no way to get all aliases from DNS. If your
machine's hostname (as returned by the hostname command) is already fully
qualified you shouldn't need to set fqdn. This flag is off by default."

In the debian/rules for sudoers fqdn is turned on with the "--with-fqdn"

Regards
chuck