yii2/apps/advanced/environments/dev/backend/config/main-local.php

<?php
return array(
	'modules' => array(
//		'debug' => array(
//			'class' => 'yii\debug\Module',
//		),
	),
	'components' => array(
		'log' => array(
			'targets' => array(
//				array(
//					'class' => 'yii\log\DebugTarget',
//				)
			),
		),
	),
);