Recently had a problem with Yii2's migrate when trying to connect to a local database.

[root@example.com yii-application]# ./yii migrate
Yii Migration Tool (based on Yii v2.0.11.2)

Error: SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: Name or service not known

Searched a lot on the web and everything pointed to a recent system update. I'd just done one and was worried that it'd broken something. As it turned out it was completely unrelated. I had configured the database connection settings in the common folder but I had forgotten that the console section of Yii2 uses its own configuration outside if the common/frontend/backend part.

The reason for the error was simply that Yii2 could not resolve the hostname in the default configuration.

return [
	'components' => [
		'db' => [
			'class' => 'yii\db\Connection',
			'dsn' => 'mysql:host=host_address;dbname=database_name',
			'username' => 'username',
			'password' => 'password',
			'charset' => 'utf8'
		],

I added the settings from common and Hey Presto! everything works.