报错如下：

[root@node2 ~]# kubeadm join 192.168.20.168:6443 --token ls16mt.ig5noemzhuflpoew     --discovery-token-ca-cert-hash sha256:a6e9a3a32b18ed86d4ee730ff382f89a99fe8d277ff33fecf68146962d211374
W1012 14:08:48.532035    9151 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 SystemVerification]: this Docker version is not on the list of validated versions: 20.10.18. Latest validated version: 19.03
error execution phase preflight: [preflight] Some fatal errors occurred:
	[ERROR Swap]: running with swap on is not supported. Please disable swap
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
To see the stack trace of this error execute with --v=5 or higher

解决方案： 

swapoff -a    # will turn off the swap 
kubeadm reset
systemctl daemon-reload
systemctl restart kubelet
iptables -F && iptables -t nat -F && iptables -t mangle -F && iptables -X  # will reset iptables

再重新把node2加入到master集群

 加入集群成功后，在master查询节点