k8s 集群 ssh 免密登录访问
（1）检查是否开启SSH服务
命令：ps -e|grep ssh 查看SSH服务是否开启，
或者通过命令：service sshd status 可以查看某个服务的状态。
（2）安装SSH服务,有就跳过 嘿嘿嘿
通过 yum 安装，命令：yum install ssh
> 客户端 yum install -y openssh-client yum -y install openssh-client
> 服务器 yum install -y openssh-server yum -y install openssh-server
（3）修改SSH配置文件
命令： vim /etc/ssh/sshd_config，找到 PermitRootLogin without-password 修改为 PermitRootLogin yes
或者：sed -i 's/#PermitRootLogin yes/PermitRootLogin yes/g' /etc/ssh/sshd_config
（4）登录 master、node1、node2、node3，每个节点都执行。
ssh-keygen -t rsa （ssh-keygen这里一路回车就行）
ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.101.120 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.101.121 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.101.122 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.101.123 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub a@192.168.101.120 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub a@192.168.101.121 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub a@192.168.101.122 &&
ssh-copy-id -i ~/.ssh/id_rsa.pub a@192.168.101.123
（5）重启SSH服务
命令： systemctl restart sshd 或 service ssh restart
（6）免密登录测试
ssh 192.168.101.120 ssh 192.168.101.121
ssh 192.168.101.122 ssh 192.168.101.123
master
node1
node2
node3
