Kubernetes worker node is NotReady due to CNI plugin not initialized - kubernetes

Question

I'm using kind to run a test kubernetes cluster on my local Macbook.
I found one of the nodes with status NotReady:
$ kind get clusters
mc
$ kubernetes get nodes
NAME STATUS ROLES AGE VERSION
mc-control-plane Ready master 4h42m v1.18.2
mc-control-plane2 Ready master 4h41m v1.18.2
mc-control-plane3 Ready master 4h40m v1.18.2
mc-worker NotReady <none> 4h40m v1.18.2
mc-worker2 Ready <none> 4h40m v1.18.2
mc-worker3 Ready <none> 4h40m v1.18.2
The only interesting thing in kubectl describe node mc-worker is that the CNI plugin not initialized:
Conditions:
Type Status LastHeartbeatTime LastTransitionTime Reason Message
---- ------ ----------------- ------------------ ------ -------
MemoryPressure False Tue, 11 Aug 2020 16:55:44 -0700 Tue, 11 Aug 2020 12:10:16 -0700 KubeletHasSufficientMemory kubelet has sufficient memory available
DiskPressure False Tue, 11 Aug 2020 16:55:44 -0700 Tue, 11 Aug 2020 12:10:16 -0700 KubeletHasNoDiskPressure kubelet has no disk pressure
PIDPressure False Tue, 11 Aug 2020 16:55:44 -0700 Tue, 11 Aug 2020 12:10:16 -0700 KubeletHasSufficientPID kubelet has sufficient PID available
Ready False Tue, 11 Aug 2020 16:55:44 -0700 Tue, 11 Aug 2020 12:10:16 -0700 KubeletNotReady runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady
message:Network plugin returns error: cni plugin not initialized
I have 2 similar clusters and this only occurs on this cluster.
Since kind uses the local Docker daemon to run these nodes as containers, I have already tried to restart the container (should be the equivalent of rebooting the node).
I have considered deleting and recreating the cluster, but there ought to be a way to solve this without recreating the cluster.
Here are the versions that I'm running:
$ kind version
kind v0.8.1 go1.14.4 darwin/amd64
$ kubectl version
Client Version: version.Info{Major:"1", Minor:"16+", GitVersion:"v1.16.6-beta.0", GitCommit:"e7f962ba86f4ce7033828210ca3556393c377bcc", GitTreeState:"clean", BuildDate:"2020-01-15T08:26:26Z", GoVersion:"go1.13.5", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.2", GitCommit:"52c56ce7a8272c798dbc29846288d7cd9fbae032", GitTreeState:"clean", BuildDate:"2020-04-30T20:19:45Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"linux/amd64"}
How do you resolve this issue?

Answer 1

Most likely cause:
The docker VM is running out of some resource and cannot start CNI on that particular node.
You can poke around in the HyperKit VM by connecting to it:
From a shell:
screen ~/Library/Containers/com.docker.docker/Data/vms/0/tty
If that doesn't work for some reason:
docker run -it --rm --privileged --pid=host alpine nsenter -t 1 -m -u -n -i sh
Once in the VM:
# ps -Af
# free
# df -h
...
Then you can always update the setting on the docker UI:
Finally, your node after all is running in a container. So you can connect to that container and see what kubelet errors you see:
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6d881be79f4a kindest/node:v1.18.2 "/usr/local/bin/entr…" 32 seconds ago Up 29 seconds 127.0.0.1:57316->6443/tcp kind-control-plane
docker exec -it 6d881be79f4a bash
root#kind-control-plane:/# systemctl status kubelet
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/kind/systemd/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: active (running) since Wed 2020-08-12 02:32:16 UTC; 35s ago
Docs: http://kubernetes.io/docs/
Main PID: 768 (kubelet)
Tasks: 23 (limit: 2348)
Memory: 32.8M
CGroup: /docker/6d881be79f4a8ded3162ec6b5caa8805542ff9703fabf5d3d2eee204a0814e01/system.slice/kubelet.service
└─768 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet
/config.yaml --container-runtime=remote --container-runtime-endpoint=/run/containerd/containerd.sock --fail-swap-on=false --node-ip= --fail-swap-on=false
...
✌️

Answer 2

I encountered this scenario. Master is Ready but the worker node's status are not. After some investigation, i found out that the /opt/cni/bin is empty - there is no network plugin for my worker node hosts. Thus, i installed this "kubernetes-cni.x86_64" and restarted kubelet service. This solved the "NotReady" status of my worker nodes.

Answer 3

Stop and disable apparmor & restart the containerd service on that node will solve your issue
root#node:~# systemctl stop apparmor
root#node:~# systemctl disable apparmor
root#node:~# systemctl restart containerd.service