ssh-keygen和ssh-copy-id实现SSH无密钥登陆

生成公钥和私钥文件

[root@localhost ~]# ssh-keygen -t rsa # -t选项指定需要加密的类型为rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
/root/.ssh/id_rsa already exists.
Overwrite (y/n)? y^H
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
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:
d5:5d:58:30:a7:45:a3:53:a8:ec:5d:89:19:7d:db:bb root@localhost.localdomain
The key's randomart image is:
+--[ RSA 2048]----+
|              =B*|
|           . ++Bo|
|          o oo* =|
|         . o o.+.|
|        S . . . .|
|           . . . |
|                .|
|               E |
|                 |
+-----------------+

生成密钥对文件

[root@localhost ~]# cd .ssh/
[root@localhost .ssh]# ll
total 12
-rw------- 1 root root 1675 Nov 16 23:39 id_rsa
-rw-r--r-- 1 root root  408 Nov 16 23:39 id_rsa.pub
-rw-r--r-- 1 root root  396 Nov 16 23:31 known_hosts

将公钥文件id_rsa.pub,copy到需要无密码登陆的服务器上

[root@localhost ~]# ssh-copy-id -i id_rsa.pub remoteIP
copy完成后会在远程服务器的.ssh/目录下生成authorized_key文件

到此为止，已经实现了两台服务器之间互相信任，可以适用于rsync的自动备份环境中。