tomcat cannot change port 8080 to 80
I found a working solution:
sudo touch /etc/authbind/byport/80
sudo chmod 500 /etc/authbind/byport/80
sudo chown tomcat7 /etc/authbind/byport/80
https://stackoverflow.com/questions/23272666/tomcat7-bind-to-port-80-fails-in-ubuntu-14-04lts