在本文中，我们将在 Linux 和 Ubuntu 服务器之间配置无密码身份验证。

配置环境

我们要在没有密码的情况下可以登录的机器。

我们要登录到备份服务器的机器。

配置无密码身份验证：

登录到dbserver 。

生成一个没有任何密码短语的 RSA 公钥。

[oracle@dbserver ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/oracle/.ssh/id_rsa):
Created directory '/home/oracle/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/oracle/.ssh/id_rsa.
Your public key has been saved in /home/oracle/.ssh/id_rsa.pub.
The key fingerprint is:
ca:2a:87:fc:7b:98:ae:d7:95:b3:35:b3:36:89:db:b4 oracle@dbserver.test.local
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|                 |
|                 |
|                 |
|        S.       |
|     . .+ +      |
| . . +o. =.=     |
|  + =.o oo=.     |
|  .B=o  .oE.     |
+-----------------+
[oracle@dbserver ~]$

以上命令在 ~/.ssh 目录中生成两个文件。
将生成的 RSA 公钥 id_rsa.pub 文件传输到备份服务器。

[oracle@dbserver ~]$ scp .ssh/id_rsa.pub backupadm@backupserver:/home/backupadm/.ssh/rsa_dbserver_oracle
The authenticity of host 'backupserver (backupserver)' can't be established.
RSA key fingerprint is a2:38:20:d9:f6:93:04:fe:e5:09:cc:5d:b5:9a:7c:4c.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'backupserver' (RSA) to the list of known hosts.
backupadm@backupserver's password:
id_rsa.pub                                                           100%  409     0.4KB/s   00:00
[oracle@dbserver ~]$

现在，连接到备份服务器并将 rsa_dbserver_oracle 合并到 ~/.ssh/authorized_keys。

backupadm@backupserver:~$ cd .ssh
backupadm@backupserver:~/.ssh$ cat rsa_dbserver_oracle >> authorized_keys

连接到 dbserver 并尝试与备份服务器连接。

[oracle@dbserver ~]$ ssh backupadm@backupserver
Welcome to Ubuntu 14.04 LTS (GNU/Linux 3.13.0-24-generic x86_64)
* Documentation:  https://help.ubuntu.com/
  System information as of Sat Apr  2 21:10:02 PKT 2016
  System load:  0.02              Processes:           246
  Usage of /:   3.6% of 36.54GB   Users logged in:     1
  Memory usage: 16%               IP address for eth0:192.168.229.128
  Swap usage:   0%
  Graph this data and manage this system at:
    https://landscape.canonical.com/
Last login: Sat Apr  2 20:26:45 2016 from dbserver
backupadm@backupserver:~$

我们已经在Linux 服务器之间配置无密码 SSH 登录。