Change wordpress Multisite default site from side id 1 to side id 2

Current site Id defines the primary network id. You can have more than one network if you use a multi-network plugin. Current blog id defines the primary blog within the primary network. To change the main blog to ‘2’ (if you only have one network) you want your defines like this:

define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 2 );