Warning: Debug mode will cause the log files to be more verbose, thus increasing in size daily. It is not recommended to leave debug mode on for extended periods of time. Please disable this after your issue is resolved.
Windows and Linux:
1) Modify (with a text editor) your log4j.properties file located in <tomcat-dir>/webapps/ehelpdesk/WEB-INF/classes.
2) Near the end of the file, uncomment the following line by removing the # (to enable it).
#log4j.logger.net.grouplink=DEBUG
The uncommented line will look like this:
log4j.logger.net.grouplink=DEBUG
3) Save file and restart Tomcat service.
Note: (See attached screenshot for example)