I’m running a site on a different CMS and we are switching to WordPress soon. At the moment, there are sites like domain.at, sub1.domain.at and sub2.domain.at, served by one installation of the old system – it detects and redirects subdomains automatically.
WordPress now runs at a (physical) directory, like domain.at/wordpress, and these links will be changed in the settings and the .htaccess when going live.
My question: If I want to prepare the subdomains on WordPress via MultiSite and I choose the subdomain option, how do I have to configure WordPress and will it have any effects on the live system?
If you choose subdomains, then you will have to configure wildcard subdomains on your server. That is pretty much going to be the end of your current subdomains. Well, not entirely. If you configure sub1.domain.at and sub2.domain.at before *.domain.at then sub1 and sub2 should probably still work. However, you cannot WordPress and another system running them at the same time. (Again, well, maybe but it will be very tricky – I do not recommend it.)
wpbeginner.com has a nice guide to setting up multisite. But you pretty much only need to find wp-config.php and add this:
define( 'WP_ALLOW_MULTISITE', true );
Then go Tools > Network Setup and configure stuff. If you skipped enabling wildcard domains then you can pre-make your new subdomains in the WordPress admin area but all sub-sites will not work. When you are ready to switch over, enable wildcard subdomains and you are now switched to WordPress multisite.
