The Web container in a Geronimo server is an integrated Tomcat/Jetty server. You can configure the embedded web container by using different GBeans. This can be done either from Console or via editing configuration files.
Starting from v2.2, Geronimo leverages server.xml from Tomcat for ease usability. Configurations to Web listeners, Clustering and Tomcat Enginee can be achieved through the same process as for a standalone Tomcat Web container. While, for configurations such as Valves, virtual hosts, JNDI and so on, you will use the GBean approach just like in Geronimo v2.1.