Umbraco-CMS/src/Umbraco.Web.UI/config/log4net.config

<?xml version="1.0"?>
<log4net>
	<root>
		<priority value="Debug"/>
		<appender-ref ref="AsynchronousLog4NetAppender" />
	</root>


	<!--To Change the way logging works for certain namespaces, insert a new logger like: -->
	<!--
	<logger name="Umbraco.Core">
		<level value="WARN" />
	</logger>-->

	<appender name="AsynchronousLog4NetAppender" type="Umbraco.Core.Logging.AsynchronousRollingFileAppender, Umbraco.Core">
		<file value="App_Data\Logs\UmbracoTraceLog.txt" />
		<lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
		<appendToFile value="true" />
		<rollingStyle value="Date" />
		<maximumFileSize value="5MB" />
		<layout type="log4net.Layout.PatternLayout">
			<conversionPattern value="%date [%thread] %-5level %logger - %message%newline" />
		</layout>
	</appender>
</log4net>