On Fri, Sep 14, 2018 at 9:43 AM, Gianluca Cecchi <gianluca.cec...@gmail.com>
wrote:

> On Thu, Sep 13, 2018 at 7:53 AM Edward Haas <eh...@redhat.com> wrote:
>
>>
>>
>> On Mon, Sep 10, 2018 at 5:53 PM, Gianluca Cecchi <
>> gianluca.cec...@gmail.com> wrote:
>>
>>> Hello,
>>> supposing to have ovirt-ng node 4.2.6 and that ovirtmgmt config
>>> regarding DNS servers has to be updated, what is the correct way to proceed?
>>>
>>
>> DNS should be editable from the network attachment window.
>>
>
> Thanks for your answer Edward.
> What do you mean with "network attachment window"?
> a) Network > Networks, then select ovirtmgmt line and edit, putting DNS
> info (that is empty right now)
> or
> b) Compute > Hosts, then select host1 line, click on host1 name, then
> Network Interfaces and Setup Host Networks. then edit ovirtmgmt > DNS
> Configuration (that is empty right now)
> or what?
>

I meant (b). Option (a) is there to apply the same DNS entries over all
hosts for that specific network.
I do not see a problem of using both.
If you add a new host, Engine will read the existing DNS entries from the
host and persist them. (you will see them in the setup-networks window (b)).
Upgraded systems (hosts have been added before DNS configuration was
available) will have it empty and you will need to explicitly set it.


> In my case they are both empty, but when I installed hosts I configured
> them
>
>
>> They are applied only for the network which "owns" the default-route for
>> that host.
>>
>
> This is typically ovirtmgmt network, as in my case, I think.
>

Yes, but one can change the management network (which owns the
default-route).


>
>
>> The values are added through ifcfg, therefore its logic of adding it to
>> resolv.conf is used.
>>
>
> I have also opened a case for another environment where I'm using RHV-H
> hosts, that should be quite similar to ovirt-node-ng
> In that environment one of the original M$ based dns server was changed
> (that was the one I had as primary) creating some latency problems.
> Using setup host networks generated big problems, especially if doing on
> the host where hosted engine was running.
> I verified that a safe way to modify DNS config is:
> - evacuate VMs from host
> - put host into maintenance
> - change dns settings in setup host networks
> - reboot the host
> - activate the host
>
> I do not see a reason to pass all these steps unless we have a bug.
The DNS entry are supposed to be applied immediately through ifcfg,
rebooting is an precaution to make sure it has been correctly persisted.
And if the management network is not serving VM/s, then no VM evacuation is
needed.

I guess the risk here is the management network editing, which is sensitive
(Engine looses connectivity and unexpected behaviour may occur).
If there is a problem with this scenario, I would consider it a bug.


> This way the "persistent" files are initially updated and then at the
> reboot the ifcfg and resolv.conf files are correctly updated
> If you are interested my case is 02179117
>

I could not find such a BZ.

>
> Also in that environment the config pages (hosts and logical network of
> cluster) had empty DNS entries....
>
> I have not understood if the hosts in "setup host network" (and also
> ovirtmgmt logical network) having empty DNS config is a bug or it's me not
> understanding the workflow when adding a host to the oVirt environment.
>

As far as I remember, when adding a host (that reports the nameservers),
the DNS entries learned are added to the Engine config and used when
sending the first setup-networks to VDSM.
But there were several iterations of this flow, perhaps it changed (will
check).


> Gianluca
>
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