How to set up A-record on a dedicated server?

Question

Domain Name System

The domain is bought, and the server in other place.
At the registrar, I registered the NS server provider.
How to change A-record on the server?
On a debian 9 server
Here is the answer from tech. support
"Then the A record has to be updated in your dedicated server."

Answer 1

Domain name registration, DNS zone hosting and server hosting are three independent things, you can host the DNS zone from one hoster or registrar and host the server from another. You need to manage records in the DNS zone, including the A-record of your server, where it is actually hosted.
You need to
1. Find out which DNS server the NS records for your domain are looking at at the domain registrar, this can be done using whois. It is for them that the whole world is looking for records in your DNS zone. If they point to the wrong place, then you can change NS records at the domain registrar (not at the hoster of the DNS zone, and even more so not at the hoster of your server, unless you host the domain zone at the registrar).
2. Make sure that the NS-records in your zone match those registered with the registrar. If they do not match or point to the wrong place, you need to change it either in the zone or at the registrar (they must also point to the provider on which you manage your DNS zone and must match the NS records at the registrar).
3. In the DNS zone, you need to register or correct the A-record for your server so that it matches its new IP address.

Answer 2

At the registrar, I registered the NS server provider.

In the NS of this provider, there should be an entry of type A.

Answer 3

Cloudflare
in the domain you write them NS, they definitely have A