Custom DNS entries for kube-dns

[morallo]

Is this a request for help?: No.

What keywords did you search in Kubernetes issues before filing this one?: kube-dns custom dns entry

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Is this a BUG REPORT or FEATURE REQUEST?: FEATURE REQUEST

Kubernetes version (use kubectl version): v1.5.2

Environment:

• Cloud provider or hardware configuration: baremetal,
• OS (e.g. from /etc/os-release): Debian GNU/Linux 8 (jessie)
• Kernel (e.g. uname -a): 3.16.7
• Install tools: docker-multinode.

What happened: Entries in /etc/hosts of the nodes are not used by kube-dns. There is no way to replicate this custom DNS configuration for the cluster.

What you expected to happen: Some way to easily define custom DNS entries used by kube-dns, without deploying an additional DNS server.

Anything else we need to know:

Already considered solutions:

• Use a Service without selector and external Endpoint. It won't allow full DNS names and that won't change for the time being.
• Deploy an additional DNS server and add it to /etc/resolv.conf in all nodes. This would work, but it's not convenient for quick/testing deployments.
• Define a ConfigMap with the DNS entries and add them to the dnsmasq /etc/hosts.d. This is possible, but requires modifying kube-dns launch flags (not obvious in automated deployments like docker-multinode

Possible solutions:

• Implement a special ConfigMap to declare custom entries on a cluster-wide level and make kube-dns look it up.
• kube-dns imports node's /etc/hosts entries, like it does for /etc/resolv.conf. This is not very elegant and doesn't scale, but it replicates a capability currently existing in non containerized system administration.

[morallo]

Reading this, I don't know if this is already in the works.

@thockin could you clarify the status? Thanks!

[cmluciano]

This is recently added to kube-dns here. It will be configurable through a config-map. This functionality should land in the 1.6 release of Kube.

[morallo]

Thank you @cmluciano :-)

However, I think it's not the same feature. That new option allows to pass nameserver. I was referring to the possibility of passing custom name/address pairs, without setting up a DNS server.

[thockin]

@bowei

[bowei]

@morallo -- it would be great to write up a example of what you are looking for and we can go from there.

• If they are in the cluster.local domain, it might not be a good idea given the potential for name clash.
• If they are in a separate domain (e.g. acme.local.), there is a proposal coming that will allow you to designate optional stub domains that have their own custom name servers. In that case, you can run your own dnsmasq for that domain and it will be incorporated into the namespace.

[bowei]

Open the issue on kubernetes/dns, so it will be more visible to the DNS work (kube-dns has been split off into a separate repo)...

[morallo]

Thanks all for the replies.
Follow-up issue in kubernetes/dns: kubernetes/dns#55