If you ever need to serve Tomcat applications through Apache2, here is a quick guide on how to do this on Ubuntu.

First, install mod-jk:

sudo apt-get install libapache2-mod-jk
sudo a2enmod jk

Then, edit workers.properties

sudo vi /etc/libapache2-mod-jk/workers.properties

and adapt the following values (assuming you have installed the openjdk):

workers.tomcat_home = /usr/share/tomcat6
workers.java_home = /usr/lib/jvm/java-6-openjdk

Then, mount the site using JkMount. Do

sudo vi /etc/apache2/sites-enabled/000-default

and then add the following line

JkMount /path/to/app/* ajp13_worker

And update the mod-jk settings in jk.load. do

sudo vi /etc/apache2/mods-available/jk.load

and update to file to read like this

LoadModule jk_module /usr/lib/apache2/modules/mod_jk.so
JkWorkersFile /etc/libapache2-mod-jk/workers.properties
JkLogFile /var/log/apache2/mod_jk.log
JkLogLevel error

Update the server.xml with

sudo vi /etc/tomcat6/server.xml

and then uncommenting the line

<connector port="8009" protocol="AJP/1.3" redirectPort="8443" />

Finally, restart the services

sudo /etc/init.d/apache2 restart
sudo /etc/init.d/tomcat6 restart

References

http://www.docshare.com/doc/197611/Installing-Tomcat6-on-Ubuntu-with-Jk-Connecto

http://ubuntuforums.org/showthread.php?t=422472

http://rcpeters.blogspot.com/2009/05/installing-apache2-and-tomcat6-on.html