DNS clustering is part of setting up a server environment. cPanel has built-in support for DNS clustering to make it easy to deploy centralized nameservers, or have multiple nameservers receive DNS zone updates from one server. This article will help you understand setting up and managing a DNS cluster from command line.

Setting up a Cluster

From the remote nameserver:

You generally don't need to do anything other than enable clustering in WHM. You want the client servers to sync TO this server, not from it. Most of the time, the remote server will be your primary nameserver running cPanel DNSONLY.

From the client:

There are a few files involved in setting up a DNS cluster. Keep in mind that novice users may prefer to use WHM  > Configure Cluster, but this article is focused on the command line.

• /var/cpanel/cluster/root/config/xxx.xxx.xxx.xxx : The file (named after the IP of the remote nameserver) containing the user, hostname, and remote hash
• /var/cpanel/cluster/root/config/xxx.xxx.xxx.xxx-dnsrole : The file containing the sync action to the remote nameserver (standalone or sync)
• /etc/wwwacct.conf : File containing the delegated nameservers for new zones created
• /var/cpanel/resellers-nameservers : list of nameservers for resellers (overrides /etc/wwwacct.conf for zones created by accounts for that reseller)
• /var/cpanel/useclusteringdns : Blank file indicating that DNS clustering is enabled (presence of file indicates yes, absence indicates no)

If the server is also going to be a nameserver itself, you will need to enable named in WHM > Service Manager (/etc/chkserv.d/chkservd.conf, set named to '1').

1)  Create a file in /var/cpanel/cluster/root/config as the IP of the remote server. Get the remote access hash for the remote nameserver (/root/.accesshash, located on the remote server) and add it to the file under the cluster user (assuming 'root') and its hostname. In this case, the remote server's IP is 6.7.8.9, so I'm going to create a file called /var/cpanel/cluster/root/config/6.7.8.9 and have it contain:

root
ns1.mynameserver.com
1429r23c1fdec38012a574be14382fd5
14f24bc86f86af9273575677c53aff83
4dc0d2d24cc8b1a7fe275acdb18e8ae8
71298146e796566a0a9fa0ea92644f11
aeceeb5f6eb489f2bb477b783a5a97c0
b24644193bb58b682c28113aa1e0e79f
59b190962fca3fcb2efb13d58d103374
3b68072ffe65a2a58cfa285fa69edeae
aff9e1922e0664acb86698c2c2884191
6cd9bd139252ec83833d07337117b898
ac071d28446cae6531e4dbeebdbe1aa2
511a689a4e2b24c7880a113694618920
a690f5b6bca11863fbc0d5b0d9a0a110
2b75426ca67984898afb71fc86c3ad75
c4a435525fc0f393ec317adbcbf4b99a
ce4b64d04c2f23766ecfb1ca4c9d09ac
36f66070c2ed55362338a1d26315c37a
91af3d1723149727d2e1756233340a57
4d1432bbfa61356b8a4b656abe817cb5
80d40d86c23cc3f4f86e74766c6d1cd6
66d2a4f89773beb02e6f856c9ae13e29
ca3e12219298e51d92f7ee9e7c645b27
dc70e2c151be6d4949d38379f6897d84
1fa9afec98cd6965300a058d77fd792b
5f47b6b791c8739ac4a18064a4420455
cc4bdf1ccf0e91d30fa7fa23b0efd168
2546f63b55f385bab0910711476d
123 Numerology.
dc3e
8ec406c3e388a5639d1f71fd3f47ae8f
b2ebc449921c906602963ed802ca20e1

*Keep in mind that if you're a user other than root, you'd substitute 'root' in the path name for the actual user setting up the cluster.

All of this can also be done via WHM > Configure Cluster as well.

Managing DNS Zones

Synchronize a zone:

You generally want to synchronize a zone if changes were made and you want to push it out to your nameserver cluster. This is essentially the same as going into WHM > Synchronize DNS Records:

/scripts/dnscluster

Running this command by itself will give you a list of options for synchronizing, just as you get in WHM:

• syncall : sync all zones with all cluster servers. This will find the zone with the largest serial and copy it to all nameservers in the cluster
• syncalllocal : Finds the zone in the cluster with the highest serial number and copies it to the local server only (instead of to all servers in the cluster) – /scripts/dnscluster syncalllocal –full
• synczone : Syncs one zone to all servers in the cluster, using the zone with the highest serial number throughout the cluster
• synczonelocal – Syncs one zone locally, using the zone with the highest serial number throughout the cluster

So for instance, if you have a zone for mydomain.com on your hosting server and you want to synchronize it to all the nameservers in your cluster, you'd run:

/scripts/dnscluster synczone domain.com

Edit a DNS Zone:

To edit a zone, open /var/named/domainname.com.db in a text editor and make your changes. Remember to increment the serial number up by one, so that the correct zone it sync'ed to the nameserver cluster. The serial looks like this:

; cPanel 11.24.4-STABLE_36281
; Zone file for domainnmame.com
$TTL 14400
@      86400	IN      SOA     ns.mynameserver.com. me.mynameserver.com. (
		2009082500	; serial, todays date+todays
		86400		; refresh, seconds
		7200		; retry, seconds
		3600000		; expire, seconds
		86400 )		; minimum, seconds

Then use /scripts/dnscluster to copy the zone up to your nameserver cluster. (see above examples)

Removing a DNS zone:

/scripts/killdns domainname.com

Adding a DNS zone:

/scripts/adddns –domain domainname.com

You can also use the  –ip and –reseller flags to indicate what IP and nameservers to use. For usage, just run /scripts/adddns and the help will display.

Additional resources:

http://docs.cpanel.net/twiki/bin/view/AllDocumentation/WHMDocs/ConfigureCluster

http://twiki.cpanel.net/twiki/pub/AllDocumentation/TrainingResources/TrainingSlides09/DNS_Cluster_Configuration.pdf