What is the password for the Tomcat admin webapp?

You have to modify tomcat-users.xml in your $TOMCAT_HOME/conf directory to add an administrative role as in following example:

<tomcat-users>
  <user name="scott" password="tiger" roles="admin" />
  <user name="role1" password="tomcat" roles="role1"  />
  <user name="both"  password="tomcat" roles="tomcat,role1" />
</tomcat-users>