问题描述：
在搭建k8s集群时，将共工作节点添加到主节点是报如下错误：
couldn‘t validate the identity of the API Server

原因：
默认token有效期24小时，过期之后，该token就不可用了，需要重新创建token。如果没有过期，也可以通过重新创建token解决

解决方案：

# master 查看节点检查token是否有效
kubeadm token list
# 生成新的token和命令。然后在node重新执行
kubeadm token create --print-join-command

执行结果：

[root@master ~]# kubeadm token list
TOKEN                     TTL         EXPIRES                     USAGES                   DESCRIPTION                                                EXTRA GROUPS
ag8915.91ayg7fogy9fffne   23h         2020-10-12T04:35:36-04:00   authentication,signing   The default bootstrap token generated by 'kubeadm init'.   system:bootstrappers:kubeadm:default-node-token
[root@master ~]# kubeadm token create --print-join-command 
W1011 04:43:25.926122   21015 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
kubeadm join 192.168.136.201:6443 --token 17wwni.taqxzqa3our1wh92     --discovery-token-ca-cert-hash sha256:1472821b3c34f13bc5d7264a737739e9854195b1856a00d2256c79d25118b2e

在 node节点中执行新的token和命令
kubeadm join 192.168.136.201:6443 --token 17wwni.taqxzqa3our1wh92 --discovery-token-ca-cert-hash sha256:1472821b3c34f13bc5d7264a737739e9854195b1856a00d2256c79d25118b2e

[root@node1 ~]# kubeadm join 192.168.136.201:6443 --token ag8915.91ayg7fogy9fffne     --discovery-token-ca-cert-hash sha256:1472821b3c34f13bc5d7264a737739e9854195b1856a00d2256c79d25118b2e
W1011 04:43:30.597584   18709 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
	[WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
	[WARNING Hostname]: hostname "node1" could not be reached
	[WARNING Hostname]: hostname "node1": lookup node1 on 8.8.8.8:53: read udp 192.168.136.202:59744->8.8.8.8:53: i/o timeout
error execution phase preflight: couldn't validate the identity of the API Server: expected a 32 byte SHA-256 hash, found 31 bytes
To see the stack trace of this error execute with --v=5 or higher
[root@node1 ~]# kubeadm join 192.168.136.201:6443 --token 17wwni.taqxzqa3our1wh92     --discovery-token-ca-cert-hash sha256:1472821b3c34f13bc5d7264a737739e9854195b1856a00d2256c79d25118b2e9
W1011 04:44:08.357838   18781 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
	[WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
	[WARNING Hostname]: hostname "node1" could not be reached
	[WARNING Hostname]: hostname "node1": lookup node1 on 8.8.8.8:53: no such host
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

添加成功