首先安装如下软件
yum -y install openssh-clients
否则没有 ssh-copy-id 命令
ssh-keygen 产生公钥与私钥对.
ssh-copy-id 将本机的公钥复制到远程机器的authorized_keys文件中，ssh-copy-id也能让你有到远程机器的home, ~./ssh , 和 ~/.ssh/authorized_keys的权利
该测试以root用户测试，如需其他用户的无密码SSH登录，执行切换到相应用户模式操作即可。
验证测试环境：
192.168.1.41 pgxlsrv1
192.168.1.42 pgxlsrv2
192.168.1.43 pgxlsrv3
第一步:在本地机器上使用ssh-keygen产生公钥私钥对
[root @pgxlsrv1 ~]# ssh-keygen
[root @pgxlsrv2 ~]# ssh-keygen
[root @pgxlsrv3 ~]# ssh-keygen
第二步:用ssh-copy-id将公钥复制到远程机器中
-i：指定公钥文件
#pgxlsrv1
[root @pgxlsrv1 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv1
[root @pgxlsrv1 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv2
[root @pgxlsrv1 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv3
#pgxlsrv2
[root @pgxlsrv2 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv2
[root @pgxlsrv2 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv1
[root @pgxlsrv2 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv3
#pgxlsrv3
[root @pgxlsrv3 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv3
[root @pgxlsrv3 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv1
[root @pgxlsrv3 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@pgxlsrv2
注意: ssh-copy-id 将key写到远程机器的 ~/ .ssh/authorized_key.文件中
第三步: 登录到远程机器不用输入密码
#pgxlsrv1
[root @pgxlsrv1 ~]# ssh pgxlsrv1
[root @pgxlsrv1 ~]# ssh pgxlsrv2
[root @pgxlsrv1 ~]# ssh pgxlsrv3
#pgxlsrv2
[root @pgxlsrv2 ~]# ssh pgxlsrv2
[root @pgxlsrv2 ~]# ssh pgxlsrv1
[root @pgxlsrv2 ~]# ssh pgxlsrv3
#pgxlsrv3
[root @pgxlsrv3 ~]# ssh pgxlsrv3
[root @pgxlsrv3 ~]# ssh pgxlsrv1
[root @pgxlsrv3 ~]# ssh pgxlsrv2
------- 通过如上三步即可实现主机之间的无密码SSH登录 --------------
使用 SSH-Key 登录远程服务器
rsync使用密钥文件(id_rsa)来同步文件
rsync -Pav -e “ssh -i $HOME/.ssh/somekey” username@hostname:/from/dir/ /to/dir/
