When you add or delete a client, always make your changes in the data files stored on your master DNS server. Do not make changes or edit the files on your slave servers because those will be automatically updated from the master server based on your changing the SOA serial number.
For example, to add the host rigel to the doc.com domain, do the following.
Create a /etc/resolv.conf file on rigel.
Add dns to the hosts line of rigel's /etc/nsswitch.conf file
Add an address (A) record for rigel to the master server's hosts file.
rigel IN A 192.168.112
Add any additional optional records for rigel to the master server's hosts file.
Optional records could include the following.
Mail exchange (MX)
Well known services (WKS)
Host information (HINFO)
Add a PTR record for rigel to the hosts.rev file.
Increment the SOA serial number in the master server's hosts and hosts.rev files.
Reload the server's data.
Either reboot the server or type the following.
# kill -HUP `cat /etc/named.pid`
To remove a client from a DNS domain do the following.
Remove dns from the hosts line of the machine's nsswitch.conf file.
Remove the machine's /etc/resolv.conf file.
Delete the records for that machine from the master server's hosts and hosts.rev files.
If the machine has CNAME records pointing to it, those CNAME records must also be deleted from the hosts file.
Set up replacements for services supported by the removed machine.
If the machine is a master server, mail host, or host for any other necessary process or service, you must take whatever steps are necessary to set up some other machine to perform those services.