[root@localhost ~]# docker swarm join --token SWMTKN-1-10s4 10.10.185.111:2377
Error response from daemon: error while validating Root CA Certificate: x509: certificate has expired or is not yet valid
It is because the cluster time is out of sync
[root@localhost ~]# yum -y install ntp ntpdate
Next, synchronize the time and run it again
[root@localhost ~]# ntpdate cn.pool.ntp.org
22 Dec 09:53:13 ntpdate[7658]: step time server 111.230.189.174 offset 4811.754411 sec
[root@localhost ~]# docker swarm join --token SWMTKN-1-103xblwtdac0zck6h8s4 10.10.185.111:2377
This node joined a swarm as a manager.
[root@localhost ~]#