What are main functions of a DNS server? 

DNS:

DNS(Domain Name System) records are used to maintain the information of your server and help it to connect to the internet.

They provide an easy way to connect to any website by just remembering the domain name of the site rather than the complicated ip address.

The main function of DNS Record is that it maps the domain name to the ip address of the site and it also points back from the ip address to the domain name.

Dns records helps in connecting the user website to the outside world.

Keeping the dns records update is also necessary as they contain essential information with them.

Functions:

1.   To answer all DNS queries, either authoritatively, or non-authoritatively, with the suitable return code.

 
2.   To forward and pass on some queries to other DNS servers.
 

3.   To decline queries that do not seem to authentic.
 

4.   Storing all domain information in a file system and normally performing a regular backup of that information.
 

5.   To log successes, failures, warnings, and errors in DNS transactions.
 

6.   To update all domain informations that is submitted by an authorized source, and to reject unauthorized sources.
 

7.   To cache DNS information according to RFC guidelines.
 

8.   To frequently update other DNS servers by sharing the most current zone information if authorized, and to decline sharing if not authorized.