1、在Client上root用户执行ssh-keygen命令，生成建立安全信任关系的证书。
Client端
# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase): <-- 直接输入回车
Enter same passphrase again: <-- 直接输入回车
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
49:9c:8a:8f:bc:19:5e:8c:c0:10:d3:15:60:a3:32:1c root@Server
注意：在程序提示输入passphrase时直接输入回车，表示无证书密码。
上述命令将生成私钥证书id_rsa和公钥证书id_rsa.pub，存放在用户家目录的.ssh子目录中。
2. 将服务器Client的公钥证书id_rsa.pub复制到机器Server的root家目录的.ssh子目录中
Client端
# scp -p /root/.ssh/id_rsa.pub root@121.40.125.251:/root/.ssh/
root@192.168.0.20's password: <-- 输入机器Client的root用户密码
id_rsa.pub 100% |**************************| 218 00:00
Server端
# mv /root/.ssh/id_rsa.pub /root/.ssh/authorized_keys
或者 cat id_rsa.pub >authorized_keys
经过以上2步，就在机器Client的root和机器Server的root之间建立安全信任关系。下面我们看看效果：
Client端
# scp -i /root/ .ssh/id_rsa text root@192.168.0.20:/root
text 100% |**************************| 19 00:00
若ssh端口非22端口，请使用-P参数后跟端口号
Ok!