A number of DHCP linux workstation hosts in our environment were not updating DNS.

Logs in SSSD showed that the Dynamic DNS child was failing with status 256.

Further investigation into the logs (with debug turned up past 5) showed that the issue seems to be that SSSD is attempting to update both host and PTR DNS records on the Windows DNS servers for the loopback address (127.0.0.1).

 

Dyndns Config in /etc/sssd/conf.d/<file>.conf is:

 

[domain/example.com]

Ad_hostname = host.fqdn

Dyndns_update = true

Dyndns_update_ptr = true

Dyndns_ttl = 3600

Dyndns_iface = <adapter name>

 

 

have the following in their hosts file:

 

# /etc/hosts

127.0.0.1  localhost

127.0.0.1  host.fqdn  host

198.168.x.x host.fqdn  host

 

Tested workstations are running SSSD 1.16.1 on Ubuntu 18.04.1 LTS.

 

Removing the second 127.0.0.1 line and reloading SSSD resolved the issue.

I understand that having 127.0.0.1 against the FQDN is unusual, but this “feature” is unfortunately required by a vendor product we are using.

Is it possible for SSSD dyndns logic to be updated so that it ignores loopback IPs?