IBM i: Updating DNS without Operational Assistant

There are no native ("green screen") commands to update DNS entries on the IBM i; you must use Operational Assistant. But, for older servers, this can be a problem. For example, I could not get Operational Assistant for V5R4 to load onto Windows 7. And Operational Assistant for V5R4 will not update DNS entries for V4R5. This tip shows you where the DNS entries are stored on the IBM i server so that you can update them yourself.

I'm going to use example.com for my examples as it is a domain name reserved for examples!

For V4R5, the DNS entries for example.com are stored in this file:

/qibm/userdata/os400/dns/EXAMPLE.COM.DB

For V5R4, the DNS entries are stored here:

/qibm/userdata/os400/dns/ns/EXAMPLE.COM.DB

If you use the WRKLNK command, you can look at this file using option 5 or edit it with option 2. Here is an example from a server running V5R4:

 ************Beginning of data**************
;*************************** iSeries Navigator ****************************
;This file was written by iSeries Navigator on Jul 27, 2011
;*************************** iSeries Navigator ****************************
$ORIGIN example.com.
 
(The next two lines are actually one line in the file.)
example.com. IN SOA falcon.example.com.
postmaster.eagle.example.com. ( 1165351125 10800 3600 604800 86400 )
 
IN NS eagle.example.com.
IN NS falcon.example.com.
IN A 93.184.216.119
IN MX 10 example.example.com.imap IN A 192.168.23.10
pop IN A 192.168.23.10
smtp IN A 192.168.23.10
www IN A 93.184.216.119
falcon IN A 192.168.23.15
eagle IN A 192.168.23.10


;*************************** iSeries Navigator ****************************
;; Data from the "Other Records" page
;*************************** iSeries Navigator ****************************
 ************End of Data********************

This file is based on standard BIND format, although the spacing of the blanks is not the same. I'll explain what some of this data means but a full explanation is beyond the scope of this post.

Our example company has two IBM i servers, Eagle (at 192.168.23.10) and Falcon (at 192.169.23.15). Eagle is hosting the mail server, also referred to as imap.example.com, pop.example.com and smtp.example.com. The web site, which uses either a blank server name (i.e. example.com) or the regular name (www.example.com) are hosted outside the firewall at IP address 93.184.216.119. Keep in mind that you will need an entry for each possible system name as DNS will not look further if the name is not present in this table. The exception is the IBM i host table (CFGTCP option 10) which is either looked at first (*LOCAL) or second (*REMOTE), depending on the value in CFGTCP option 12.

This example company did not have a Windows server when this was set up. DNS was set up on both Eagle and Falcon for redundancy and their IP addresses loaded into the firewall as the name servers for DHCP connections. Of course, the reason for doing this is that the DNS entries for servers are different inside the firewall than they are outside. For example, Falcon's IP address outside the firewall might be 93.184.216.120 and Eagle's could be 93.184.216.121.

If you have not used Operational Assistant to set up DNS, I can't help you. This blog post is about changing entries, not setting up new entries. Let me know, through comments or email, if you have any questions.