Comment 3 for bug 1929523

Hello:

In this test we are using Ubuntu image, if I'm not wrong:
[ 0.000000] Linux version 5.3.0-26-generic (buildd@lgw01-amd64-039) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #28~18.04.1-Ubuntu SMP Wed Dec 18 16:40:14 UTC 2019 (Ubuntu 5.3.0-26.28~18.04.1-generic 5.3.13)

IMO, we should implement a more robust method to check the system DNS. In Ubuntu (and other advance images), we can use "resolvectl". For example, when I add two DNS to the subnet:

* Before renewing the IP
root@ubuntu:~# resolvectl dns
Global:
Link 2 (ens3): 10.20.0.2 10.20.0.3

* Update the subnet DNS nameservers
(overcloud) [stack@undercloud-0 ~]$ openstack subnet set --dns-nameserver 3.3.3.3 subnet1
(overcloud) [stack@undercloud-0 ~]$ openstack subnet set --dns-nameserver 3.3.4.4 subnet1

* Refresh the IP in the VM
root@ubuntu:~# dhclient -r && dhclient
root@ubuntu:~# resolvectl dns
Global: 3.3.4.4 3.3.3.3
Link 2 (ens3): 10.20.0.2 10.20.0.3

We can parse the command exit and use those values.

Regards.