WIP - Coredns user config

[erikwilson]

For #462

Provides a coredns-user configMap to separate k3s config from user config.

Example:

cat >/var/lib/rancher/k3s/server/manifests/user-coredns-config.yaml <<EOF
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns-user
  namespace: kube-system
data:
  Rewrite: |
    rewrite name regex [a-zA-Z.]+\.dev0\.be\.lan traefik.kube-system.svc.cluster.local
EOF

[warmchang]

apiVersion: apps/v1 is better for k8s-v1.14.x, 😃

[mrueg]

Can we decouple the image bump from the feature add? I would like to see a more recent version of coredns soon :)

[mlebrun]

@erikwilson appreciate you opening this! is there any way I can help in order to get this PR to move forward? Very excited and appreciate you taking time to do this!

[galal-hussein]

@erikwilson I am wondering if we should do this to all manifests, the local storage PR also include a configmap that can be configured for different nodes https://github.com/rancher/k3s/pull/816/files#diff-0683dbb4f157e849170880c2b3a8049eR94

[erikwilson]

Thanks @mlebrun! The PR kind of stalled due to limitations with CoreDNS config. I would like to support a hosts directive for users (or at least maintain our own node hosts independent of user hosts settings), but it appears that the hosts plugin can only be used once per zone. Perhaps the PR should move forward anyways tho if the basic usage looks okay.

Unfortunately @galal-hussein I think this is using some CoreDNS specific tricks using the reload and import directives so not sure how portable it is. It would be nice to find a better way to customize manifests tho, since naming and upgrades are an issue.

[mlebrun]

Right, if some version of this functionality could move forward, we would at least have something in the meantime, albeit maybe not perfect. But I would take that over having to modify my CoreDNS config on server restarts! As always, let me know if there's anything I can do outside of gentle nudging 😃

[rpocase]

@erikwilson Any plans to revisit this PR? This feature would be extremely valuable for my dev tooling.

[blaggacao]

Is this somehow superseded? (eg. by what's yet to come in #1899)

[ieugen]

Is this PR still relevant?
#1899 has been merged.
If not maybe it can be closed.

[dereknola]

Closing this PR as out-of-date (by 2 years)
Native config file support exists. #1899

[ChristianCiach]

I don't see how #1899 has any relation to this PR. I need to modify the coredns config to do this: https://coredns.io/2017/05/08/custom-dns-entries-for-kubernetes/

But the config.yaml doesn't help me with this, doesn't it?

Edit: I see, you're probably talking about --resolv-conf=/etc/rancher/k3s/resolv.conf. Yes, this could help with my use-case, too.

Edit 2: I've confused resolv.conf with /etc/hosts, so no, this doesn't help me in realizing https://coredns.io/2017/05/08/custom-dns-entries-for-kubernetes/

[iwilltry42]

Coming here today as I'm struggling with finding a proper way of modifying the CoreDNS configmap for k3d (e.g. to inject host.k3d.internal and records for the LB and registries, etc.).
Up to now, we're modifying the NodeHosts field of the configmap (as the hosts plugin can only be used once per server), but this feels unsafe, as K3s is also updating this field every now and then.
It works ok so far, but I think having a separate field or even an extra configmap for user-defined hosts would be great for this :)