You have a couple of options:

1. Remove the out-of-the-box ROOT/ directory from tomcat and rename your war file to ROOT.warbefore deploying it.
2. Deploy your war as (from your example) war_name.war and configure the context root in conf/server.xml to use your war file :

   <Context path="" docBase="war_name" debug="0" reloadable="true"></Context>

The first one is easier, but a little more kludgy. The second one is probably the more elegant way to do it.

If Tomcat is set to autodeploy, you don’t have to worry about option 2.

Tomcat7 bind to port 80 fails in Ubuntu 14.04LTS

Following works:

apt-get install authbind

First, set AUTHBIND=yes in /etc/default/tomcat7 file

sudo touch /etc/authbind/byport/80
sudo chmod 500 /etc/authbind/byport/80
sudo chown tomcat7 /etc/authbind/byport/80