Install Centminmod and ngnix only in the local network?

Just setup the domains you want via centmin.sh menu option 2 as outlined at Nginx Vhost & NSD DNS Setup - CentminMod.com LEMP Nginx web stack for CentOS They aren't live unless you edit your domain's DNS to point to centminmod server's IP address so will no interfere with your live domain operation.

Then edit each domain's vhost file at /usr/local/nginx/conf/conf.d/newdomain.com.conf and /usr/local/nginx/conf/conf.d/newdomain.com.ssl.conf (if you set yes to ssl) and add to server_name listing additional domain names you want to test from i.e. test.newdomain.com.

would change from

Code:

server {
  server_name newdomain.com www.newdomain.com;

to

Code:

server {
  server_name newdomain.com www.newdomain.com test.newdomain.com;

then only update DNS for test.newdomain.com to point to centminmod server's IP address. Then after testing is done and you want to switch live domain to centminmod copy, just update DNS for newdomain.comto point to centminmod server's IP address as well

If you want to preview newdomain.com on new centminmod server without updating DNS, on Windows PC edit your windows HOSTS file at c:\Windows\System32\Drivers\etc\hosts (see guide at Modify your hosts file | Knowledge Center | Rackspace Hosting or install Hostman app HostsMan - abelhadigital.com which can manage the file too and allows easy dns flushing when you make changes to the hosts file.

c:\Windows\System32\Drivers\etc\hosts contents to preview without DNS update

Code:

centminmodserver-ip-address newdomain.com

to disable preview comment it out and flush dns for your system

Code:

#centminmodserver-ip-address newdomain.com

Hostsman app to flush dns and edit the c:\Windows\System32\Drivers\etc\hosts file

 

each server over network needs same local hosts file edit too to bypass DNS