How to change logging level of JBoss 5.1 internals

Uncomment in $JBOSS_HOME/server/<config>/conf/jboss-log4j.xml:

   <category name="org.jboss.system">
     <priority value="TRACE" class="org.jboss.logging.XLevel"/>
   </category>
   <category name="org.jboss.ejb.plugins">
     <priority value="TRACE"/>
   </category>