title: grails how to configure log4j to log to tomcat logs
body: <p>Every time that I start up my grails application, using the production environment on my tomcat6 server I see the following error in /var/log/tomcat6/catalina.out:</p>
  
  <pre><code>log4j:ERROR setFile(null,true) call failed.
  java.io.FileNotFoundException: stacktrace.log (Permission denied)
  ...
  ...
  </code></pre>
  
  <p>I gather that this is becaues log4j is attempting to create a log file and doesn't have the required permissions. </p>
  
  <p>Ideally I would like the log files for my application to go to either the existing tomcat log (/var/log/tomcat6/catalina.out) or to go to a separate file in the /var/log/tomcat6 directory. </p>
  
  <p>How can I change the location of the log4j logs with the minimal amount of configuration possible? i.e. I don't want to define a complete appender with it's own output pattern, I just want to change the location of the log files.</p>