在 CentOS7 環境，K8S 的 Master 透過 kubeadm join 啟動後，先查看 pods 處於 Pending 狀態
> kubectl get pods --all-namespaces
//or
> kubectl get pods -n kube-system
//輸出
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-66bff467f8-c79f7 0/1 Pending 0 24h
kube-system coredns-66bff467f8-ncpd6 0/1 Pending 0 24h
kube-system etcd-k8s-master 1/1 Running 0 24h
kube-system kube-apiserver-k8s-master 1/1 Running 0 24h
kube-system kube-controller-manager-k8s-master 1/1 Running 0 24h
kube-system kube-proxy-mnsjm 1/1 Running 0 24h
kube-system kube-scheduler-k8s-master 1/1 Running 0 24h
以及查看 nodes，k8s-master 呈現 NotReady
> kubectl get nodes
//輸出
NAME STATUS ROLES AGE VERSION
k8s-master NotReady master 44h v1.18.6
解決這問題，只要安裝 flannel Pod 網路插件即可
(Flannel is an overlay network provider that can be used with Kubernetes.)
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
稍等一會，再查看 pods 輸出， coredns就會正常運行
> kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-66bff467f8-c79f7 1/1 Running 0 45h
coredns-66bff467f8-ncpd6 1/1 Running 0 45h
etcd-ssdnodes-adamouyang 1/1 Running 1 45h
kube-apiserver-ssdnodes-adamouyang 1/1 Running 1 45h
kube-controller-manager-ssdnodes-adamouyang 1/1 Running 1 45h
kube-flannel-ds-amd64-4jnsx 1/1 Running 0 4m45s
kube-flannel-ds-amd64-s8m9x 1/1 Running 0 4m45s
kube-proxy-mnsjm 1/1 Running 1 45h
kube-proxy-tzwqs 1/1 Running 1 68m
kube-scheduler-ssdnodes-adamouyang 1/1 Running 1 45h
以及查看 node
> kubectl get node
NAME STATUS ROLES AGE VERSION
k8s-master Ready master 45h v1.18.6
若執行過程有發生問題，可查看日誌
journalctl -f -u kubelet.servic