$defaultUrlHost in /var/www/localhost/htdocs/twiki/lib/TWiki.cfg should be set to whatever the ServerName is in /etc/apache2/conf/apache2.conf with http:// prepended and the Listen variable (like 80, or 81, or 8081) appended from /etc/apache2/conf/apache2.conf
$wikiHomeUrl can also be set to something sensible
einfo "and be sure to read"
Can't we do both? Set a nice default, and tell them to look at the manual?