Error: "unable to load bootstrap kubeconfig: stat /etc/kubernetes/kubelet.conf: no such file or directory" results in Supervisor Control Plane Node NotReady status

Products

• VMware vSphere Kubernetes Service

Issue/Introduction

• One of the three Supervisor Cluster control plane nodes is in a NotReady state, causing etcd to lose quorum. Containers on the affected node are in an exited state, and few pods are in a terminating state.

• Error from the supervisor tab in vCenter UI shows the following :

Cluster test is unhealthy:
Get "http://localhost:1080/external-cert/<supervisor_control_plane_ip>/6443/version?timeout=2m0s": context deadline exceeded (Client.Timeout exceeded while awaiting headers)

Error : Configured Supervisor Control plane VM's Workload Network Configuration error (since MM/DD/YYYY, hh:mm:ss PM) CoreDNS configuration failed on Master node with identifier <supervisor-node-id>. Details: failed to retrieve current version from etcd.

• Output of kubectl get nodes shows below:

root@### [ ~ ]# kubectl get nodes
NAME     STATUS     ROLES                   AGE   VERSION
<node-1>  Ready     control-plane,master    571d  v1.25.6+vmware.wcp.2
<node-2>  NotReady  control-plane,master    571d  v1.25.6+vmware.wcp.2
<node-3>  Ready     control-plane,master    571d  v1.25.6+vmware.wcp.2

• SSH to the Supervisor node and check the kubelet log using command "journalctl -xeu kubelet"

>kubelet[34395]: E0528 hh:mm:ss.ss  34395 server.go:425] "Client rotation is on, will bootstrap in background"
>kubelet[34395]: E0528 hh:mm:ss.ss  34395 bootstrap.go:265] "Client rotation is on, will bootstrap in background"
>kubelet[34395]: E0528 hh:mm:ss.ss  34395 run.go:74] "command failed" err="FAILED_TO_RUN_KUBELET: unable to load bootstrap kubeconfig: stat /etc/kubernetes/kubelet.conf: no such file or directory"
>kubelet[34395]: E0825 hh:mm:ss.ss  34395 bootstrap.go:266] part of the existing bootstrap client certificate in /etc/kubernetes/kubelet.conf is expired: YYYY-MM-DD

Environment

• VMware vSphere Kubernetes Service
• VMware vSphere Supervisor 8.x

Cause

The node is NotReady because the kubelet service fails to start due to an expired certificate in /etc/kubernetes/kubelet.conf. This prevents the kubelet from connecting to the API server, causing containers to exit, pods to terminate, and etcd to lose quorum since only two of the three nodes are operational.

Resolution

1. Open an SSH session to all Supervisor control plane nodes.

2. Validate the kubelet certificate is valid using the below command

   1. openssl x509 -in /var/lib/kubelet/pki/kubelet-client-current.pem -text -noout

3. Edit the kubelet.conf file on the affected Supervisor Control Plane Node with below changes:

   1. vi /etc/kubernetes/kubelet.conf

   2. Change "client-certificate-data" to "client-certificate" and "client-key-data" to "client-key"

   3. Make sure client-certificate and client-key point to a valid certificate path at /var/lib/kubelet/pki/kubelet-client-current.pem instead of certificate content in double encoded format.

Before (Old Configuration)

• • • • • • client-certificate-data: #.....<Certificate-content in double encoded format>
          • client-key-data: #....<Certificate-content in double encoded format>
            
            

After (New Configuration)

1. • • • • • apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: [REDACTED]
    server: https://###.###.###.###:6443
  name: <cluster name>
contexts:
- context:
    cluster: <cluster name>
    user: system:node:<cluster name>-controlplane-####
  name: system:node:<cluster name>-controlplane-####@<cluster name>
current-context: system:node:<cluster name>-controlplane-####@<cluster name>
kind: Config
preferences: {}
users:
- name: system:node:<cluster name>-controlplane-####
  user:
    client-certificate: /var/lib/kubelet/pki/kubelet-client-current.pem
    client-key: /var/lib/kubelet/pki/kubelet-client-current.pem

             

2. Restart the kubelet service

   1. systemctl restart kubelet.service


3. Verify the kubelet is running

   1. systemctl status kubelet.service

4. Confirm containers and pods are in Running state

   1. kubectl get pods -A -o wide

   2. crictl ps -a

5. Ensure all nodes are in a Ready state

   1. kubectl get nodes -o wide