Add to the require section of your composer.json file:
"sacara/yii2-maintenance-mode": "*"
Add to your config file:
'bootstrap' => ['log', 'maintenance'],
...
'modules' => [
'maintenance' => [
'class' => 'sacara\maintenance\Module',
// optional
'maintenanceFileOn' => 'maintenance.on', // default is `maintenance.on`
],
],Create a file in the @web directory named maintenance.on to activate the maintenance mode.