coreDNS CrashLoopBackoff

I have set up the cluster without error and am running through Lab 2.1. I noticed that the pods for coreDNS are failing.
I am running the nodes on bare metal.
Debug info is:
**kubectl get pod -n kube-system
NAME READY STATUS RESTARTS AGE calico-etcd-wr2cf 1/1 Running 3 13h calico-kube-controllers-57c8947c94-g2lbc 1/1 Running 3 13h calico-node-lsjm9 2/2 Running 17 13h calico-node-zhgnd 2/2 Running 9 13h coredns-576cbf47c7-56thg 0/1 CrashLoopBackOff 54 13h coredns-576cbf47c7-nmznf 0/1 CrashLoopBackOff 54 13h etcd-nuc1 1/1 Running 4 13h kube-apiserver-nuc1 1/1 Running 4 13h kube-controller-manager-nuc1 1/1 Running 3 13h kube-proxy-ct89j 1/1 Running 3 13h kube-proxy-lbdxr 1/1 Running 5 13h kube-scheduler-nuc1 1/1 Running 3 13h
kubectl describe pods -n kube-system coredns-576cbf47c7-56thg
Name: coredns-576cbf47c7-56thg Namespace: kube-system Priority: 0 PriorityClassName: <none> Node: nuc1/10.10.0.53 Start Time: Sat, 29 Dec 2018 23:06:32 +1100 Labels: k8s-app=kube-dns pod-template-hash=576cbf47c7 Annotations: <none> Status: Running IP: 192.168.21.71 Controlled By: ReplicaSet/coredns-576cbf47c7 Containers: coredns: Container ID: docker://5491ac6a53be7f653036af7baaecfb318679882d3ad4b60c7c02b8846f3a4f9d Image: k8s.gcr.io/coredns:1.2.2 Image ID: docker-pullable://k8s.gcr.io/[email protected]:3e2be1cec87aca0b74b7668bbe8c02964a95a402e45ceb51b2252629d608d03a Ports: 53/UDP, 53/TCP, 9153/TCP Host Ports: 0/UDP, 0/TCP, 0/TCP Args: -conf /etc/coredns/Corefile State: Waiting Reason: CrashLoopBackOff Last State: Terminated Reason: Error Exit Code: 1 Started: Sun, 30 Dec 2018 12:39:49 +1100 Finished: Sun, 30 Dec 2018 12:39:50 +1100 Ready: False Restart Count: 54 Limits: memory: 170Mi Requests: cpu: 100m memory: 70Mi Liveness: http-get http://:8080/health delay=60s timeout=5s period=10s #success=1 #failure=5 Environment: <none> Mounts: /etc/coredns from config-volume (ro) /var/run/secrets/kubernetes.io/serviceaccount from coredns-token-zwdp6 (ro) Conditions: Type Status Initialized True Ready False ContainersReady False PodScheduled True Volumes: config-volume: Type: ConfigMap (a volume populated by a ConfigMap) Name: coredns Optional: false coredns-token-zwdp6: Type: Secret (a volume populated by a Secret) SecretName: coredns-token-zwdp6 Optional: false QoS Class: Burstable Node-Selectors: <none> Tolerations: CriticalAddonsOnly node-role.kubernetes.io/master:NoSchedule node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 13h default-scheduler Successfully assigned kube-system/coredns-576cbf47c7-56thg to nuc1 Warning NetworkNotReady 13h (x8 over 13h) kubelet, nuc1 network is not ready: [runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady message:docker: network plugin is not ready: cni config uninitialized] Normal Pulled 13h (x4 over 13h) kubelet, nuc1 Container image "k8s.gcr.io/coredns:1.2.2" already present on machine Normal Created 13h (x4 over 13h) kubelet, nuc1 Created container Normal Started 13h (x4 over 13h) kubelet, nuc1 Started container Warning BackOff 12h (x255 over 13h) kubelet, nuc1 Back-off restarting failed container Normal SandboxChanged 3h31m (x2 over 3h31m) kubelet, nuc1 Pod sandbox changed, it will be killed and re-created. Warning BackOff 3h31m (x3 over 3h31m) kubelet, nuc1 Back-off restarting failed container Normal Pulled 3h30m (x2 over 3h31m) kubelet, nuc1 Container image "k8s.gcr.io/coredns:1.2.2" already present on machine Normal Created 3h30m (x2 over 3h31m) kubelet, nuc1 Created container Normal Started 3h30m (x2 over 3h31m) kubelet, nuc1 Started container Normal Pulled 3h29m (x4 over 3h30m) kubelet, nuc1 Container image "k8s.gcr.io/coredns:1.2.2" already present on machine Normal Created 3h29m (x4 over 3h30m) kubelet, nuc1 Created container Normal Started 3h29m (x4 over 3h30m) kubelet, nuc1 Started container Warning BackOff 3h5m (x124 over 3h30m) kubelet, nuc1 Back-off restarting failed container Warning FailedMount 92m kubelet, nuc1 MountVolume.SetUp failed for volume "coredns-token-zwdp6" : couldn't propagate object cache: timed out waiting for the condition Normal SandboxChanged 91m (x2 over 92m) kubelet, nuc1 Pod sandbox changed, it will be killed and re-created. Normal Pulled 90m (x4 over 91m) kubelet, nuc1 Container image "k8s.gcr.io/coredns:1.2.2" already present on machine Normal Created 90m (x4 over 91m) kubelet, nuc1 Created container Normal Started 90m (x4 over 91m) kubelet, nuc1 Started container Warning BackOff 57m (x169 over 91m) kubelet, nuc1 Back-off restarting failed container Normal SandboxChanged 49m (x2 over 50m) kubelet, nuc1 Pod sandbox changed, it will be killed and re-created. Normal Pulled 47m (x4 over 49m) kubelet, nuc1 Container image "k8s.gcr.io/coredns:1.2.2" already present on machine Normal Created 47m (x4 over 49m) kubelet, nuc1 Created container Normal Started 47m (x4 over 49m) kubelet, nuc1 Started container Warning BackOff 4m49s (x214 over 49m) kubelet, nuc1 Back-off restarting failed container
Comments
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@bryonbaker ,
You can try to delete the 2 coredns pods, and they will be re-created.
Are you in Lab 2.1 of LFD259?
Thanks,
-Chris0 -
Hi,
The issue is actually thoroughly documented in the CoreDNS web site. It is caused because CoreDNS is detecting a loopback and it terminates. It is expected behaviour.The solution is to change the DNS setting in /etc/resolv.conf. For those using Ubuntu I have documented what to do here as it can be tricky - especially with Ubuntu Desktop edition.
There are other ways to solve it but in the end I set up an external DNS server with bind9 for resolving hostnames. Overkill I know.1
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