BIND (named) not reloading zone with error loading from master file failed: CNAME and other data

Written by Claudio Kuenzler - 0 comments

Published on September 13th 2023 - Listed in DNS Linux

After updating a few DNS records of a domain in BIND 9 (9.16 on Debian 11), I realized a few hours later that the changes were not applied.

By looking closer at the syslog logs, the following error showed up:

Sep 10 14:25:38 bindserver named[3307095]: dns_master_load: /etc/bind/example.com.hosts:28: znuny.example.com: CNAME and other data
Sep 10 14:25:38 bindserver named[3307095]: zone example.com/IN: loading from master file /etc/bind/example.com.hosts failed: CNAME and other data
Sep 10 14:25:38 bindserver named[3307095]: zone example.com/IN: not loaded due to errors.

Whenever there are such errors, a zone file (/etc/bind/example.com.hosts in this case) should be manually verified. For this purpose, there is the command named-checkzone:

root@bindserver:~# named-checkzone example.com /etc/bind/example.com.hosts
dns_master_load: /etc/bind/example.com.hosts:28: znuny.example.com: CNAME and other data
dns_master_load: /etc/bind/example.com.hosts:31: clement.example.com: CNAME and other data
zone example.com/IN: loading from master file /etc/bind/example.com.hosts failed: CNAME and other data
zone example.com/IN: not loaded due to errors.

The same error as seen in syslog before shows up. Two errors were detected in lines 28 and 31, mentioning a problem with "CNAME and other data".

Looking closer at the subdomains of the mentioned CNAME records, there are actually two entries for that subdomain (znuny and clement):

root@bindserver:/etc/bind# grep znuny example.com.hosts
znuny.example.com.   IN      TXT     "v=spf1 +a +a:target.example.com ~all"
znuny            IN    CNAME    target.example.com.

root@bindserver:/etc/bind# grep clement example.com.hosts
clement         IN    CNAME    target.example.com.
clement                IN      TXT     "v=spf1 +a +a:target.example.com ~all"

Another DNS record, a TXT record for SPF, is present at the same time of the CNAME record. The problem? The same subdomain cannot co-exist as CNAME and as another entry. From the CPANEL knowledge base (although I do not use Cpanel myself), there's a helpful information:

This error indicates that you have a domain name in your zone file that owns both a CNAME record and a record of another type.

As I needed to keep the SPF entries for handling outgoing e-mails used for these subdomains, the CNAME was adjusted to an A record pointing to the original target IP address. After this change, the zone file check worked and rndc reload worked, too.

root@bindserver:~# named-checkzone example.com /etc/bind/example.com.hosts
zone example.com/IN: loaded serial 2023091302
OK

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