The location of alfresco.log and share.log is in the current directory when starting tomcat, which is already a very stupid thing to do since you will find these files anywhere your shell will be when you run tomcat's startup.sh.
Apparently it is not possible to fix this location to something sensible without changing the log4j.properties file in alfresco webapps ??? I tried to use a "dev-log4j.properties or log4.properties in shared/classes/alfresco/extension as advised by an old answer but it doesn't work. Is there a clean way to define this location or should administrators cd to a suitable log directory whenever they start tomcat ?