Here are all of the important file locations in Debian Linux when you install Tomcat 7 from an "aptitude install" command.
|/var/log/tomcat7/||These are all of your log files.|
|/etc/tomcat7/||This location includes: server.xml, web.xml, tomcat-users.xml, context.xml|
|/etc/default/tomcat7||This file contains your Java JVM options, and Tomcat impersonation! JAVA_OPTS, TOMCAT7_USER, TOMCAT7_GROUP|
|/usr/share/tomcat7/||This folder contains the bin and lib folders for Tomcat|
|/var/lib/tomcat7/||This folder contains the webapps folder (for WAR-file deployments), common, server, and shared folders (for server-level classpath inclusions)|
|/var/lib/tomcat7/webapps/ROOT/||This folder contains the "default" application served at: / on some configurations|
|/usr/share/tomcat7-root/||This folder contains the "default" application served at: / on some configurations|
|/usr/share/tomcat7-admin/||This is installed if you execute "aptitude install tomcat7-admin" and contains the /manager/, and /host-manager/ applications.|
I had a memory problem, so I had a hard time finding where to change the JAVA_OPTS variable. Come to find out it was in /etc/default/tomcat7!