Kubedns and node nameservers

[Todd VanderVeen]

I've setup a k8s 1.4 cluster with the kubedns addon. In-cluster resolution is working as expected, but external names cannot be resolved. As I understand it, the nodes defined nameservers are used for resolution (with the caveat that only 3 entries are permitted, with skydns taking one) outside of the cluster. Am I misunderstanding this  expected behavior, or do external nameservers need to be explicitly configured somehow?

[Tim Hockin]

kube-dns should pass-thru to whatever nameserver(s) are configured in
the node's resolv.conf

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[Matthias Rampke]

To debug, you can `kubectl exec` into a kubedns pod and inspect the /etc/resolv.conf it got.

[Todd VanderVeen]

Sorry, I should have been clearer about what I am observing. My nodes /etc/resolv.conf lists 3 name servers and 3 search domains. However, my containers show only a single name server, as specified by the kubelet. The search domain list is properly extended to 6 entries, being prefixed with the 3 expected cluster domains.

The only dns related configuration I've used are the kubelet flags:

--cluster-dns=10.3.0.10

--cluster-domain=cluster.local

What else would play into this?

Thanks,

On Tue, Oct 18, 2016 at 1:46 AM, Matthias Rampke <m...@soundcloud.com> wrote:

To debug, you can `kubectl exec` into a kubedns pod and inspect the /etc/resolv.conf it got.

On Tue, Oct 18, 2016, 01:52 'Tim Hockin' via Kubernetes user discussion and Q&A <kubernetes-users@googlegroups.com> wrote:

kube-dns should pass-thru to whatever nameserver(s) are configured in
the node's resolv.conf

On Mon, Oct 17, 2016 at 1:11 PM, Todd VanderVeen
<todd.vanderveen@collectivemedicaltech.com> wrote:
> I've setup a k8s 1.4 cluster with the kubedns addon. In-cluster resolution
> is working as expected, but external names cannot be resolved. As I
> understand it, the nodes defined nameservers are used for resolution (with
> the caveat that only 3 entries are permitted, with skydns taking one)
> outside of the cluster. Am I misunderstanding this  expected behavior, or do
> external nameservers need to be explicitly configured somehow?
>
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Todd VanderVeen

Collective Medical Technologies

(801) 419-2288 (c)

9815 S. Monroe St. Ste. 501

Salt Lake City, UT 84070

http://www.collectivemedicaltech.com

[Todd VanderVeen]

The kube-dns pod does reflect the node's nameservers and external name resolution does work from within the container.

[Tim Hockin]

What you describe is correct - normal containers get the kube-dns as
their sole nameserver. kube-dns is responsible for forwarding DNS for
domains it does not own.

On Tue, Oct 18, 2016 at 9:21 AM, Todd VanderVeen

>>>> > email to kubernetes-use...@googlegroups.com.

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>>>
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>>
>>
>>
>>
>> --
>> Todd VanderVeen
>> Collective Medical Technologies
>>
>> (801) 419-2288 (c)
>> 9815 S. Monroe St. Ste. 501
>> Salt Lake City, UT 84070
>> http://www.collectivemedicaltech.com
>
>
>
>
> --
> Todd VanderVeen
> Collective Medical Technologies
>
> (801) 419-2288 (c)
> 9815 S. Monroe St. Ste. 501
> Salt Lake City, UT 84070
> http://www.collectivemedicaltech.com
>

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