How to split index and admin into 2 different servers?

Question

System administration

Hello!
There was a need to transfer the admin panel to another host.
In general, there are two domains site.com and adm.site.com, domains are tied to two different servers (ip). On the third - the database.
I just wanted to duplicate the engine, and make admin empty and index, respectively. But, if you just duplicate two engines, then there will be a problem with the files uploaded to the server. Although I heard somewhere that there is a "Link to the directory".
In general, there is an idea to upload all files from the first server to the second one. But how to implement it?
Or maybe there are other ways to implement the separation of the admin and index?