After restarting the device:
CODE
kubectl get node
The connection to the server x.x.x.x:6443 was refused - did you specify the right host or port?
systemctl status kube-apiserver prompts:
Unit kube-apiserver.service could not be found
There is no such service, so it is judged that the configuration file is wrong
Decided to reconstruct the K8S cluster
Solution:
CODE
# 1. Check if kubectl command is working
kubectl get node
# 2. Go to the home directory
cd ~
# 3. Check if the .kube directory exists
ll -a # List all files to check if .kube directory exists
# 4. Remove the .kube directory
rm -rf .kube/
# 5. Restart Docker service
systemctl restart docker # Restart Docker
# 6. Restart kubelet service
systemctl restart kubelet # Restart kubelet
# 7. Reset the Kubernetes setup
kubeadm reset # Reset Kubernetes cluster
# 8. Remove CNI configurations
rm -rf /etc/cni/ # Delete CNI configurations
# 9. Reinitialize Kubernetes with specific settings
kubeadm init --kubernetes-version=1.23.5 --apiserver-advertise-address=192.168.1.21 --image-repository registry.aliyuncs.com/google_containers --service-cidr=192.1.0.0/16 --pod-network-cidr=192.244.0.0/16
# 10. After successful initialization, configure Kubernetes for the user
mkdir -p $HOME/.kube # Create the .kube directory
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config # Copy admin config
sudo chown $(id -u):$(id -u) $HOME/.kube/config # Change ownership of the config file
# 11. Download the Flannel network configuration file
wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml # Download Flannel YAML file
# 12. Copy the kube-flannel.yml file to /opt and apply it
sudo cp kube-flannel.yml /opt/ # Copy the Flannel YAML file to /opt directory
kubectl apply -f /opt/kube-flannel.yml # Apply the Flannel configuration
# After these steps, check the node status
kubectl get nodes # Check if the node is ready
- Issue with Flannel and CoreDNS Pods Not Starting:
When checking the pods, Flannel and CoreDNS are not starting.
CODE
Error: Flannel is having an issue where it cannot obtain the necessary subnet lease. Specifically, the PodCIDR (assigned IP range for pods) 192.244.0.0/24 is not included within Flannel’s network configuration subnet 10.244.0.0/16.
- Fixing the Subnet Configuration:
Edit the Flannel ConfigMap: To resolve the subnet issue, the Flannel ConfigMap needs to be updated.
First, inspect the Flannel Pod:
CODE
kubectl describe pod kube-flannel-ds-99grr -n kube-flannel # Describe the Flannel pod for detailed information
Check the logs:
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kubectl logs kube-flannel-ds-fqvvv -n kube-flannel # Check the Flannel pod logs for errors
Error Explanation: The Flannel network plugin is unable to get a subnet lease because the PodCIDR 192.244.0.0/24 is not within the subnet 10.244.0.0/16 specified in Flannel’s configuration.
Solution: You can resolve this by modifying the Flannel network configuration:
Edit the Flannel ConfigMap:
CODE
kubectl edit configmap kube-flannel-cfg -n kube-flannel # Edit the Flannel ConfigMap in the kube-flannel namespace
Change the subnet in the ConfigMap to match the required PodCIDR.
After modifying the subnet in the kube-flannel-cfg ConfigMap, Flannel should be able to allocate the necessary subnets and the pods should start successfully.
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