How are DNS Records added dynamically in DNS Servers?

[Stephane Bortzmeyer]

On Mon, Sep 07, 2015 at 03:33:00PM +0530,
 Harshith Mulky <harshith.mulky at outlook.com> wrote 
 a message of 60 lines which said:

> How do System administrators add DNS Zone records in DNS Servers?

By not using outlook.com for email :-) No, I'm kidding, there are
several ways:

> Is there a specific way the records are added in DNS Servers dynamically?

* a program that you write in the langage of your choice. Every
programming langage has a DNS library and most allows dynamic updates.

* by using an already-written program which does dynamic updates. Many
DHCP servers can do so, for instance.

* using the shell with nsupdate:

#!/bin/sh

nsupdate -kKexample-dyn-update.+157+18685.private -d <<EOF
  server nsupdate.example.org
  zone dyn.example.org
  update delete mylaptop.dyn.example.org 
  update add mylaptop.dyn.example.org 300 A $new_ip_address
  send
EOF
fi