kubernetes installation issues

1. [ERROR Swap]: running with swap on is not supported. Please disable swap 
Solution: swapoff -a 

2. The connection to the server 10.76.98.43:6443 was refused - did you specify the right host or port?
Solution: Check whether kubelet service is running
If not running do $ swapoff -a  && systemctl restart kubelet
Ref: https://github.com/kubernetes/kubernetes/issues/54542 
     https://github.com/kubernetes/kubernetes/issues/23726

3. coredns pod is not running
$ kubectl --namespace=kube-system get pods
Disable SELinux and reboot
Ref: https://github.com/kubernetes/kubeadm/issues/998

4. while doing echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables,
it returns -bash: /proc/sys/net/bridge/bridge-nf-call-iptables: No such file or directory
Insert br_netfilter module
$ modprobe br_netfilter
$ echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables

5. Get a token from kubernetes master for adding new nodes
$ kubeadm token create --print-join-command
Use the command to join 

6. [ERROR Port-10250]: Port 10250 is in use
$ netstat -lnp |grep 10250
tcp6       0      0 :::10250                :::*                    LISTEN      7182/kubelet        
$ kill 10250

7. $ kubectl get nodes
Unable to connect to the server: x509: certificate is valid for 10.96.0.1, 192.168.122.21, not 10.76.98.43
Solution: $ rm $HOME/.kube/* -rf
$ cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ chown $(id -u):$(id -g) $HOME/.kube/config
Ref: https://stackoverflow.com/questions/46360361/invalid-x509-certificate-for-kubernetes-master

8. For node related errors: $ kubectl describe nodes <node-name>

9. Master is NotReady state
Check kubelet service status: $ systemctl status -l kubelet 
If the error is "Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady message:docker: network plugin is not ready: cni config uninitialized"
Solution: $ kubectl apply --filename https://git.io/weave-kube-1.6
$ systemctl restart kubelet




. Check: https://kubernetes.io/docs/tasks/debug-application-cluster/troubleshooting/