php composer.phar require --prefer-dist sacara/yii2-maintenance "*"
or add
"sacara/yii2-maintenance": "*"
to the require section of your composer.json file.
Add to your config file:
'bootstrap' => ['log', 'maintenance'],
...
'modules' => [
'maintenance' => [
'class' => 'sacara\maintenance\Module',
],
],
...Create a file in the @web directory named maintenance to activate the maintenance mode.