环境：
三台Linux 服务器
IP Release Hostname
192.168.200.131 centos7 ceph-node1
192.168.200.130 centos7 ceph-node2
192.168.200.136 centos7 ceph-node3
配置ceph-node1无密码连接ceph-node2和ceph-node3:
[root@ceph-node1 ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): ##回车代表无需密码登陆
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase): ##回车
Enter same passphrase again: ##回车
Your identification has been saved in /root/.ssh/id_rsa. ##私钥
Your public key has been saved in /root/.ssh/id_rsa.pub. ##公钥
The key fingerprint is:
SHA256:FGrYUe6qiaKaRXz4sp/HLWJJvDeUsGaV+++EKe9fKwc root@ceph-node1
关于 ssh-keygen的参数解释：http://www.cnblogs.com/wangkongming/p/6362397.html
[root@ceph-node1 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub root@192.168.200.130
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.200.130's password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh 'root@192.168.200.130'"
and check to make sure that only the key(s) you wanted were added.
在客户端的/root目录下就是出现 .ssh文件夹，下面是对应的authorized_keys文件。
在ceph-node1上ssh到ceph-node2,这样就能实现无密码访问了。
[root@ceph-node1 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub root@192.168.200.136