Migrate cPanel DNS-Only Nameservers

wswd

Well-Known Member
Aug 9, 2005
142
16
168
cPanel Access Level
Root Administrator
Hi all,

We run a 4 nameserver cPanel-only DNS cluster. Those nameservers were installed on a 32-bit OS, which of course affects the updates now.

What is the best means of reinstalling the nameserver boxes (OS and cPanel) whilst avoiding downtime?

Thanks!
 

cPanelMichael

Administrator
Staff member
Apr 11, 2011
47,908
2,218
463
Hello,

Could you verify how the cluster is currently configured? Do you have the ability to obtain an additional server temporarily for migration purposes?

Thank you.
 

wswd

Well-Known Member
Aug 9, 2005
142
16
168
cPanel Access Level
Root Administrator
Hi Michael,

I'm not sure what you mean by how it is currently configured. I do have access to temporary servers.

Thanks!
 

cPanelMichael

Administrator
Staff member
Apr 11, 2011
47,908
2,218
463
Hello,

For instance, is the cluster configured with direct links? There's a document here that references the configuration types:

Guide to DNS Cluster Configurations - cPanel Knowledge Base - cPanel Documentation

Generally, since a cluster affords you redundancy in the event one server is down, you can simply reinstall the OS and cPanel DNS-Only on each server one at a time. Once the DNS-Only installation completes, re-add the the server via WHM Home >> Clusters >> DNS Cluster on each cPanel server that syncs it's zones to the cluster.

Thank you.
 

wswd

Well-Known Member
Aug 9, 2005
142
16
168
cPanel Access Level
Root Administrator
It's a cPanel DNS cluster, with Write-Only defined on the servers to all 4 nameservers.

Sounds good, and thanks for the help Michael! Just wanted to make sure I wasn't missing something. :)
 
  • Like
Reactions: cPanelMichael

cPanelMichael

Administrator
Staff member
Apr 11, 2011
47,908
2,218
463
Hello @wswd,

You're very welcome! Let us know if you encounter any issues during the migration.

Thank you.
 

wintech2003

Well-Known Member
PartnerNOC
Sep 15, 2010
103
28
78
Greece
cPanel Access Level
DataCenter Provider
We're also looking to replace our CentOS 6 DNS-only nameservers (was hoping we would had a stable release that supports CentOS 8 by now, to avoid having to redo this again soon) and were wondering what needs to be done in order to re-sync the newly re-installed DNS-only box, with all the records from the cPanel servers.
I guess we need to re-add it to each cPanel (web)server, and then?
"Synchronize all zones to this server only" from the DNS box?
"Synchronize all zones to all servers" from each server (I think this will break things..)
 

cPRex

Jurassic Moderator
Staff member
Oct 19, 2014
4,883
605
273
cPanel Access Level
Root Administrator
@wintech2003 - All that should need to happen is that the DNSOnly system gets added to the cluster on each webserver, and then you perform a sync from each webserver. I would run "/scripts/dnscluster --syncall" on the webserver to ensure those zones get updated to all the DNS cluster members.
 

lorio

Well-Known Member
Feb 25, 2004
313
20
168
cPanel Access Level
Root Administrator
All that should need to happen is that the DNSOnly system gets added to the cluster on each webserver, and then you perform a sync from each webserver. I would run "/scripts/dnscluster --syncall" on the webserver to ensure those zones get updated to all the DNS cluster members.
The wording around the different settings in the DNS clustering function is still confusing. This hasn't changed in years.

Synchronize Changes: All changes made on this server will propagate to any server in the cluster that is linked to this server. Synchronization is one-way: changes made on another server will not propagate to this server unless Synchronize changes is selected on the other server as well.

Standalone: No changes made on this server will propagate to any other servers.

Write-only: This server will write changes to the remote server. Changes to the remote server will not propagate back to this server. Warning: Two Write-only servers that attempt to write changes to a matching record on the same remote server will cause a conflict and may corrupt data.
The cleanest scenario one would be on WHM-Server with two DNS directly linked in the DNS cluster settings.
The "DNS Role" in the dialog is defining the role of remote server when interacting with the logged-in server.
When I chose e.g. "Standalone" for ns1 and "Write-Only" for ns2, the DNS role descriptions are

I would change the description to "Standalone : No changes made on this server will propagate to the remote server."
The "any other server" is misleading, isn't it?
 

lorio

Well-Known Member
Feb 25, 2004
313
20
168
cPanel Access Level
Root Administrator
I found a different wording for DNS roles.

Synchronize — This method synchronizes records between the local server and the remote server.
Most administrators use this setting.
Standalone — This method fetches DNS records from the remote server, but does not write
records from the local server to the remote server.
Write-only — This method pushes the local server’s records to write to the remote server, but does
not query records from the remote server to write to the local server.
Synchronize (without enabling reverse relationship) is resulting in what behavior? One-Way-Sychronization, which is Write-Only with check of existing records?
 

cPRex

Jurassic Moderator
Staff member
Oct 19, 2014
4,883
605
273
cPanel Access Level
Root Administrator
Synchronize is going to send the data over to the remote system. I have found the best way to think about this is that you are controlling the sync options for the server you are working with. For example, in the following screenshot:

Screen Shot 2020-11-27 at 8.34.30 AM.png
My local server is syncing the changes to those remote DNS systems. If you logged into the DNSOnly servers themselves, you'd see the option for the webservers set to "standalone" so all zones from all webservers do not get synced to each other:

Screen Shot 2020-11-27 at 8.36.34 AM.png
 

lorio

Well-Known Member
Feb 25, 2004
313
20
168
cPanel Access Level
Root Administrator
@cPRex Thank for your answer. I personally have not activated the DNSCluster on the DNSOnly machines. So WriteOnly is used on each WHMserver.

But your idea to describe both side of connection (for the cases when a trusted relationship from DNSOnly to WHMHost is needed), might be a good input for the manual as well.
 
  • Like
Reactions: cPRex