I have recently attempted to setup a 3-node Kubernetes cluster. However, when doing so, only one of the two coreDNS services functions correctly.

$ kubectl get pods -n kube-system
NAME                                               READY   STATUS    RESTARTS   AGE
coredns-8445fcc4f-jknn4                            0/1     Running   0          15s
coredns-8445fcc4f-q9fhg                            1/1     Running   0          15s
...

One waits indefinitely trying to contact the Kubernetes API server, while the other has no issue doing so. Here are the logs of the faulty node.

$ kubectl logs coredns-8445fcc4f-jknn4 -n kube-system
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/ready: Still waiting on: "kubernetes"
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/ready: Still waiting on: "kubernetes"
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[INFO] plugin/kubernetes: waiting for Kubernetes API before starting server
[WARNING] plugin/kubernetes: starting server with unsynced Kubernetes API

The coredns configmap is as follows:

apiVersion: v1
data:
  Corefile: |
    .:53 {
        log
        errors
        health {
           lameduck 5s
        }
        ready
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           fallthrough in-addr.arpa ip6.arpa
           ttl 30
        }
        prometheus :9153
        forward . /etc/resolv.conf {
           max_concurrent 1000
        }
        cache 30
        #loop
        reload
        loadbalance
    }
kind: ConfigMap
metadata:
  creationTimestamp: "2024-06-25T20:06:12Z"
  name: coredns
  namespace: kube-system
  resourceVersion: "1261664"
  uid: f0837e49-308b-4167-89af-1a182a81aea4

I have verified that the DNS containers have the appropriate permissions and endpoints and that their /etc/resolv.conf files are correct, as per the instructions in the DNS debugging page on the kubernetes website. I have also commented out the “loop” term from the coreDNS configmap, in line with the advice from this SO answer, but the container remains unable to contact kubernetes.