Does anyone know a way to do a permanent redirect from a.example.com to b.example.com? I have other subdomains that need to remain as they are though. so:
first.
Add the following RewriteRule to your VirtualHost
RewriteEngine On
RewriteCond %{HTTP_HOST} ^first.example.com$
RewriteRule ^ http://second.example.com [R=301,L]
If you wanted to redirect first.example.com/some/url to second.example.com/some/url:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^first.example.com$
RewriteRule /(.*) http://second.example.com/$1 [R=301,L]
Recommend you use [R=302] whilst testing the rules to avoid problems with 301s getting cached by your browser.