Redirect an entire WordPress site on a subdomain, except wp-admin

Question

With .htaccess I'm trying to redirect all traffic away from a WordPress site, except traffic to wp-admin.

The goal is to redirect all traffic away from the site, but retain admin access.

I'm using .htaccess to do this, and it's working to an extent. But when trying to access wp-admin I get an internal server error.

The site is on a subdomain and this is my current code:

    RewriteEngine on
    RewriteCond %{HTTP_HOST} subdomain\.oldsite\.co\.uk$ [NC]
    RewriteCond %{REQUEST_URI} !^/wp-admin [NC]
    RewriteRule ^(.*)$ http://www.newsite.co.uk/$1 [R=301,L]

I'd be grateful for any insights.

Answer 1

Answering my own question for future reference. I couldn't get a redirect to work with .htaccess, but found some helpful troubleshooting suggestions, mainly this one: https://stackoverflow.com/a/14116956/3218102.

I ended up doing this with a modification to header.php and the functions wp_redirect and is_admin.

This is the code I added to the top of header.php:

<?php 
// Redirect everyone to new URL, except admin
if ( ! is_admin() ) {
     wp_redirect( 'http://www.newsite.co.uk/', 301 ); 
     exit;
}
?>