I installed a blog on existing.com/blog, but now they want that blog to show up on the root of newdomain.com (while keeping the main website on existing.com).

I imagine I can alias that new domain name to the old one, but how then can I tell SilverStripe to load the blog page when the request is coming for newdomain.com? (while of course also keeping all the links working, if they click links to blog posts etc)

Or will I have to set up the blog in a different way? Subsites or someting? I do want it in the same CMS though.

Maybe a little custom script. Curl the contents of existing.com/blog, rewrite the links as necessary and cache it.

Though, you'll create duplicated content which will probably do you no good.

Thank you for your suggestion. Here's what I ended up doing, for future searchers.

I left the path /blog/ on the new domain after all - so newdomain.com will redirect to newdomain.com/blog. That way I can just alias both domains, which always works, and I don't need to curl contents or rewrite links. All that was left is a little custom logic in the HomePage to redirect newdomain.com/ straight to the blog, and extending Blog in order to redirect existing.com/blog to newdomain.com/blog.

I actually thought about "hiding" the /blog/ component in all the links by overriding Blog and BlogPost's Link method, and then calling the Blog content from the HomePage, but decided not to fuss with it to avoid breaking anything. It's undoubtedly possible though, and that would be a full solution to my original issue. (With the side effect that the whole original website is available on that new domain too (except for the homepage), but that doesn't really hurt).