GAST stands for GeoNetwork’s Administrator Survival Tool and is a standalone application whose purpose is to simplify some low level tasks like change of the servlet, configuration of the JDBC account, setup the database and so on. Most of the GAST’s facilities work only for the GeoNetwork’s installation where GAST is in. This implies that if you are using a servlet container other than Jetty (like Tomcat) you will not be able to change some options (like the servlet’s name). Other facilities work for any servlet container but you have to specify the GeoNetwork’s URL into the GAST’s configuration dialog.