In order to have Tomcat listen on port 80, you either have to have it running as root (which by the way is not a very good idea), or configure a wrapper like JSCV.

Here is how you do it (This is an example using tomcat 6 please adapt to your install):

# cd /opt/apache-tomcat-6.0.16/bin/
# tar -zxvf jsvc.tar.gz
# cd jsvc-src
# chmod +x configure

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