Where is nameserver address coming from?

juju
1

I have been experimenting with deploying OpenStack-Base Ussuri charm bundle with MAAS 2.8/Juju 2.8 Ubuntu 20.04. In looking at all of the interfaces configured of the deployed machines, i keep noticing a DNS server address i have no idea where its configuration source is.

For example, I see the nameserver address of 10.80.30.251 entered for all the interfaces.

# This file is generated from information provided by the datasource.  Changes
# to it will not persist across an instance reboot.  To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
    ethernets:
        eno1:
            addresses:
            - 10.80.0.22/24
            gateway4: 10.80.0.251
            match:
                macaddress: d0:43:1e:ff:2d:2e
            mtu: 9000
            nameservers:
                addresses:
                **- 10.80.30.251**
                - 10.80.0.251
                search:
                - maas.os.adaxatech.com
            set-name: eno1
        eno2:
            match:
                macaddress: d0:43:1e:ff:2d:2f
            mtu: 1500
            set-name: eno2
    version: 2
    vlans:
        eno1.20:
            addresses:

I’ve checked all the subnet configurations on MAAS and they all do not have any dns server info configured. Where is this coming from?

2

This is coming from your subnet configuration in MAAS.

Each node provisioned by MAAS (not necessarily by Juju) will get DNS server config in netplan files according to what is configured in MAAS.

This config gets written there by cloud-init on first boot - it talks to the MAAS metadata servers to get the values in the config.

The way machines are seeded with config by MAAS on first post-installation boot is quite similar to that of cloud instances.

Is 10.80.0.251 an IP address of your MAAS host?

1 Like
3

Yes, 10.80.0.251 is the IP of my MAAS server.

Ok this is weird then and now I’m really confused because I just double checked all of the subnet configs via the maas cli and it confirms that there are no DNS servers defined in any of the subnets I have.

image

4

MAAS acts as a DNS, providing names for the machines that you deploy via MAAS. AFAIK, you don’t necessarily have to define a DNS on a subnet to get the MAAS server’s ip written as a nameserver in your netplan.

(There’s a DNS tab in the MAAS gui, which will list the things that MAAS has taken responsibility for.)

1 Like
5

So, what you’re saying is that the odd of 10.80.30.251 entry (which btw is one of the interfaces on the MAAS server) in all the netplans is MAAS arbitrarily inserting it? That seems odd.

Let me ask the question a different way:

Is it required for the MAAS server to have an interface on all the subnets defined in MAAS? Initially i only had 2 interfaces on MAAS host; 1 internal 1 external. But then I added interfaces connected to the VLANs i created in MAAS for OpenStack. Is that overkill for the MAAS host?

6

Hi @colombrican,

I think that we’re moving away from the expertise of the folks on the forum here. I’d try heading to discourse.maas.io , where you can get more detailed answers about the MAAS internals.