How to change the page using DNS?

Question

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Good day to all
We have a small network in the hostel: a router + 7 laptops + 10-12 smartphones / tablets
The role of the router is played by a netbook (CentOS 7 + OpenVPN), which is connected by wire to the channel provider and distributes the Internet to everyone else via WIFI. Adguard DNS Family Protection is registered on it as a DNS to block porn.

Two tasks need to be solved:

1. Block a couple of additional sites by opening an Adguard stub instead of the actual content
   
2. Use Google DNS instead of Adguard Family Protection for gooogle.com and youtube.com domains
   

I don't know where to even start looking. I would be grateful for any hints.

PS: Porn was blocked at the request of users from Mon to Fri and becomes available on Sat and Sun by replacing DNS from Adguard Family Protection with Google DNS

Answer 1

In general, there is usually a dhcp server on the router and it distributes the address of the DNS server - you can replace it with a local DNS server (for example, deploy pihole and configure everything there)
But if a friend understands how DNS, DHCP and networks work, he will simply statically register himself google public dns (8.8.8.8) and everything will work. You can also replace one site with another by dns (just add a record in your DNS server that will point to your IP), but there are nuances - the user can access directly by IP and then he will not care that there is such a DNS on the network, or on the site can be https and then the person immediately sees the fact that the site has been spoofed ..