How do I force Kubernetes CoreDNS to reload its Config Map after a change?

kubernetes coredns
E. Wittle picture E. Wittle · Nov 27, 2018 · Viewed 14.1k times · Source

I'm running Kubernetes 1.11, and trying to configure the Kubernetes cluster to check a local name server first. I read the instructions on the Kubernetes site for customizing CoreDNS, and used the Dashboard to edit the system ConfigMap for CoreDNS. The resulting corefile value is:

.:53 {
    errors
    health
    kubernetes cluster.local in-addr.arpa ip6.arpa {
       pods insecure
       upstream    192.168.1.3 209.18.47.61
       fallthrough in-addr.arpa ip6.arpa
    }
    prometheus :9153
    proxy . /etc/resolv.conf
    cache 30
    reload
}

You can see the local address as the first upstream name server. My problem is that this doesn't seem to have made any impact. I have a container running with ping & nslookup, and neither will resolve names from the local name server.

I've worked around the problem for the moment by specifying the name server configuration in a few pod specifications that need it, but I don't like the workaround.

How do I force CoreDNS to update based on the changed ConfigMap? I can see that it is a Deployment in kube-system namespace, but I haven't found any docs on how to get it to reload or otherwise respond to a changed configuration.

Answer

Viliam Pucik picture Viliam Pucik · Jul 9, 2020

One way to apply Configmap changes would be to redeploy CoreDNS pods:

kubectl rollout restart -n kube-system deployment/coredns

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