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centosovirt

How to change DNS servers on an oVirt CentOS 7 server?

I am currently in the process of updating and modernizing my company's internal network, and as part of this we are replacing two old Active Directory servers (serving DNS as part of their Domain Controllers role) with two new ones. This part of the upgrade has been completed: the new DCs are online, roles have been shifted over, DNS is working. For now, the old DCs are still on the network as DCs, though the plan in the medium term is for them to be demoted and removed when the time is right.

This has revealed an issue with the oVirt servers we have, though: Their DNS entries are still pointing at the (static) IP addresses of the old DCs. This became obvious as an issue when after some physical relocation of the DCs, we were unable to log onto the (AD-auth-using) oVirt console until the older DCs were also powered back on. We cannot move the IP addresses around, the oVirt servers need to be changed to use the new DCs as their DNS servers.

I have located files at /etc/resolv.conf , /etc/sysconfig/network-scripts/ifcfg-ovirtmgmt and /var/lib/vdsm/persistence/netconf/nets/ovirtmgmt , all of which contain lines with the IPs of the old DCs in, but it is not obvious which of these if any are being automatically generated. I have done reading around the subject and it is suggested that the latter of the three is the main configuration file but this is also the only one that's been modified in the last 2 years - specifically at the time when the servers were last powered up following their move.

Which, if any, of these three files should I be editing? If none, where should I be?

Solution

  • You have two options:

    1. change the DNS globally for the Logical Network marked as Default Route (typically the Management network). Go to Compute → Data Center → YourDC → Logical Networks → YourDefaultRouteNetwork → Edit and look for the DNS section. This is the preferred method.

    2. change the DNS per host. Go to Compute → Hosts → YourHost → Network Interfaces → Setup Host Networks → YourDefaultRouteNetwork and click on the pencil ✎ symbol. From there you can set the DNS servers.

    N.B.: do not attempt to change the DNS configuration directly from the host files, since this will end up with the oVirt configuration in the PostgreSQL going out of sync with the one in the hosts.