Problems : 1/ When a VM is created in a subnet with a default DNS value defined as 0.0.0.0 -> The VM file /etc/resolv.conf is not empty (as expected) but have the value 0.0.0.0 2/ When a VM is created in a subnet where the option --dns-nameserver is used to have no DNS defined at the subnet level -> The VM file /etc/resolv.conf is not empty (as expected) and will have the value of the default DNS of the UnderCloud -> More over : if a default value should has been taken it should be value of : - dns_nameservers pram in the ~/undercloud.conf file OR - DnsServers param in the ~/templates/environments/network-environment-overrides.yaml ### After the UpGrade from 16.2.1 to 16.2.3 we have done the following tests : Intro : We have used two diffèrent images to to create the tests VM : -> VM with CIRROS Image -> VM with Almalinux image Spoil : The tests show that : -> The result can depend on the VM image -> The behaviour of the VMs can be very complecated depending on the test scenario Tests détails : 1a/ Create the VM in a subnet with no DNS using the --no-dns-nameservers option -> VM Cirros : /etc/resolv.conf value at 10.10.10.10 (undercloud default DNS) -> VM Almalinux : /etc/resolv.conf value at 10.10.10.10 (undercloud default DNS) 1b/ Define the DNS subnet value as 0.0.0.0 AND then reboot the VM in the subnet with the DNS value at 0.0.0.0 -> VM Cirros : /etc/resolv.conf value at 0.0.0.0 -> VM Almalinux : /etc/resolv.conf value at empty !!! 1c/ Destroy the VM AND then deploy it again in the subnet with DNS value at 0.0.0.0 -> VM Cirros : /etc/resolv.conf value at 0.0.0.0 -> VM Almalinux : /etc/resolv.conf value at 0.0.0.0 1d/ Reboot the VM in the subnet with DNS value at 0.0.0.0 -> VM Cirros : /etc/resolv.conf value at 0.0.0.0 -> VM Almalinux : /etc/resolv.conf value at 0.0.0.0 1e/ Define the DNS subnet value as empty with the --no-dns-nameservers option AND then reboot the VM -> VM Cirros : /etc/resolv.conf value at 10.10.10.10 -> VM Almalinux : /etc/resolv.conf value at 0.0.0.0 1f/ Define the DNS subnet value at 0.0.0.0 AND then reboot the VM -> VM Cirros : /etc/resolv.conf value at 0.0.0.0 -> VM Almalinux : /etc/resolv.conf value at 0.0.0.0
I just reproduced this with a RHEL 8.4 : [cloud-user@test-dave ~]$ cat /etc/resolv.conf ; Created by cloud-init on instance boot automatically, do not edit. ; nameserver 0.0.0.0
[root@overcloud-vcontroller-0 ~]# podman exec -i ovn-dbs-bundle-podman-0 ovn-nbctl list DHCP _uuid : b172bfaa-8683-4192-b5ff-68460bb2121c cidr : "10.0.0.0/24" external_ids : {"neutron:revision_number"="1", subnet_id="197b33d2-53cf-41df-b8f2-11535e08cdc4"} options : {classless_static_route="{169.254.169.254/32,10.0.0.100, 0.0.0.0/0,10.0.0.1}", dns_server="{0.0.0.0}", lease_time="43200", mtu="1500", router="10.0.0.1", server_id="10.0.0.1", server_mac="fa:16:3e:01:35:0d"}