Configuration Files
* JAVA_HOME: default is to be set to $(java-config --jdk-home). Changing this variable allows Tomcat to run with a VM other than the system VM
* CATALINA_HOME: default is /usr/share/tomcat-x.y
* CATALINA_BASE: default is /var/lib/tomcat-x.y
* CATALINA_USER: default is tomcat
* CATALINA_LIBDIR: default is typically /usr/share/tomcat-x.y/server/lib
* CLASSPATH: default is ${CATALINA_LIBDIR}
* CATALINA_TMPDIR: default is /var/tmp/tomcat-*
* TOMCAT_START: default is "start", with alternatives being "debug", "start -security", "debug -security", or "jpda start"
* TOMCAT_STOP: default is "stop"
* CATALINA_OPTS: not set by default , can be used to pass options to Java or Tomcat