Hiding admin panel on separate domain?

Question

I have a large site, I was thinking of the safest way to hold an admin panel for a site and was wondering what if I put the admin panel on a separate site? Would google find my admin panel site just because it's hosted on the same dedicated server?

Are there sites that tell people what other domains are hosted on the same dedicated server?

example:

site.com (public)

adminsite.com (hidden from everyone else)

is this possible? Am I supposed to put a robot.txt that blocks access or what is the best practice?

Answer 1

By definition, it is impossible to have a site that is hidden from everyone else. You could do site.com/adminpanel or something. Of course, you need to have strong authentication on the admin panel no matter what.