Enable Log4j debug on initializing in Grails

In a Grails application we can set the Log4j configuration in Config.groovy. To see what is happening during the initialization process of Log4j we can set the debug property to true. The following code snippet shows this property at line 2:

// log4j configuration
log4j {
    debug = true
    appender.stdout = "org.apache.log4j.ConsoleAppender"
    appender.'stdout.layout'="org.apache.log4j.PatternLayout"
    appender.'stdout.layout.ConversionPattern'='[%r] %c{2} %m%n'
    appender.stacktraceLog = "org.apache.log4j.FileAppender"
    appender.'stacktraceLog.layout'="org.apache.log4j.PatternLayout"
    appender.'stacktraceLog.layout.ConversionPattern'='[%r] %c{2} %m%n'
    appender.'stacktraceLog.File'="stacktrace.log"
    rootLogger="error,stdout"
    logger {
        grails="error"
        StackTrace="error,stacktraceLog"
        org {
            codehaus.groovy.grails.web.servlet="error"  //  controllers
            codehaus.groovy.grails.web.pages="error" //  GSP
            codehaus.groovy.grails.web.sitemesh="error" //  layouts
            codehaus.groovy.grails."web.mapping.filter"="error" // URL mapping
            codehaus.groovy.grails."web.mapping"="error" // URL mapping
            codehaus.groovy.grails.commons="info" // core / classloading
            codehaus.groovy.grails.plugins="error" // plugins
            codehaus.groovy.grails.orm.hibernate="error" // hibernate integration
            springframework="off"
            hibernate="off"
        }
    }
    additivity.StackTrace=false
}