Question
You may receive a notification from WHM regarding your current Operating System that is not compatible with the newer version of cPanel when running DNSOnly servers.
Example:
Severity Blocker Message
FATAL Newer releases of cPanel & WHM are not compatible with your operating system. Upgrade your OS, or use the Update Preferences screen to select a Long-Term Support release for use with your OS. Starting with version 88, cPanel & WHM supports 64-bit versions of CentOS 7+, Red Hat Enterprise Linux 7+, and CloudLinux® 6+ only. Please see our OS End of Life policy for more information.
This warning appears if the WHM/cPanel server is running CentOS 6 or lower.
CentOS 6 is currently a "blocker" when updating to WHM v88 or later.
https://docs.cpanel.net/knowledge-base/cpanel-product/upgrade-blockers/
"CentOS 6 and Red Hat® Enterprise Linux (RHEL) 6
Existing cPanel & WHM servers that use CentOS 6 and Red Hat Enterprise Linux® (RHEL) 6 operating system cannot upgrade from cPanel & WHM version 86 to 88. For more information about our deprecation of CentOS 6, read our CentOS 6, CloudLinux 6 OS, and you! blog post."
How would you perform an update for the DNS Cluster Members running DNSOnly?
Answer
DNSOnly server(s) can function using CentOS 6 but will no longer receive security updates.
We would recommend replacing your DNSOnly servers with CentOS 7 servers using the DNSOnly installation.
Installation Guide:
https://docs.cpanel.net/installation-guide/cpanel-dnsonly-installation/
As a general guide, these are steps you would want to consider.
First method:
If you can create a new server and maintain the same IP address, use these general steps.
1. Create a CentOS 7 server.
2. Install DNSOnly on it.
3. Give it the same hostname as one of the CentOS 6 servers.
4. Remove the corresponding CentOS 6 server.
5. Add the new CentOS 7 server with the same hostname to the DNS Cluster.
6. Use WHM to sync all records: WHM: Home -> DNS Functions -> Synchronize DNS Records.
7. Repeat until all CentOS 6 servers are gone.
8. No other changes are needed.
Second method:
If you can only create the new server and it must have a different IP address, use these general steps.
1. Create a CentOS 7 server.
2. Install DNSOnly on it.
3. Please give it a different hostname as one of the CentOS 6 servers.
4. Add it to the DNS Cluster.
5. Use WHM to sync all records: WHM: Home -> DNS Functions -> Synchronize DNS Records.
6. Remove the corresponding CentOS 6 server it is meant to replace.
7. Modify the nameserver information at the domain registrar that gives your DNS Server authority to reflect the new hostname and IP address.
8. Modify the DNS zonefile that controls the IP address for the nameserver to reflect the new server, and remove the old.
9. Repeat until all CentOS 6 servers are gone.
Verify new DNSOnly servers are working by using a third-party site to see what they report: https://dnschecker.org/
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The first method is the 'safest' as it should not incur any time for DNS propagation.
The second method will cause DNS propagation to occur.