How to raise a subdomain on a third-party server?

Question

Apache HTTP Server

There is domain.ru deployed on the first server located in Russia. You need to deploy the ns.domain.ru subdomain on a server located in the USA from another provider. Tell me, please, what needs to be done for this?
There is an entry A ns.domain.ru - [ip address of the second server] and the usual Apache virtual host configured for this subdomain:
ServerAdmin [email protected]
ServerName ns.domain.ru
ServerAlias ​​www.ns.domain.ru
DocumentRoot /var/www /ns.domain.ru/public_html
At the same time, it does not work, for some reason it sends to the default page (index.php in the /var/www/html folder)

Answer 1

DocumentRoot /var/ns.domain.ru