[CentOS] SSH 免密钥登录

一、环境说明：

操作系统：CentOS-7-x86_64-Minimal-1611

虚拟机：VMware® Workstation 12 Pro；12.5.5 build-5234757

服务器：node1（User1），node2（User2）

二、实现内容：

node1 服务器用户 User1 可通过 SSH ，免密钥登录服务器 node2 的 User2 账户；

三、配置流程：

默认情况下，node1 上的用户 User1 想连接 node2，需要输入密码，如下：

 [User1@localhost ~]$ ssh User2@node2
 The authenticity of host 'node2 (192.168.126.141)' can't be established.
 ECDSA key fingerprint is 0c:f2:1d:5b:0a:ea:38:43:e7:d2:07:28:d8:05:8a:d6.
 Are you sure you want to continue connecting (yes/no)? yes
 Warning: Permanently added 'node2,192.168.126.141' (ECDSA) to the list of known hosts.
 User2@node2's password:
 Last login: Fri Feb  2 17:03:45 2018

1、现在通过用户 User1 在 node1 的 /home/User1 目录下生成一对公钥和私钥：

 [User1@localhost ~]$ ssh-keygen -t rsa
 Generating public/private rsa key pair.
 Enter file in which to save the key (/home/User1/.ssh/id_rsa):
 Enter passphrase (empty for no passphrase):
 Enter same passphrase again:
 Your identification has been saved in /home/User1/.ssh/id_rsa.
 Your public key has been saved in /home/User1/.ssh/id_rsa.pub.
 The key fingerprint is:
 ff:cc:0e:22:aa:79:54:d3:15:90:bd:98:2b:26:e1:35 User1@localhost.localdomain
 The key's randomart image is:
 +--[ RSA 2048]----+
 |       .+..     |
 |       . o     |
 |       . + .     |
 |   . E + .     |
 |   . + oS.       |
 |    + o ..       |
 |   . o... o     |
 |   ... . . =     |
 |  oo.     .=   |
 +-----------------+

2、然后将公钥上传给 node2 的 User2 用户：

 [User1@localhost ~]$ ssh-copy-id User2@node2
 /bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
 /bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
 User2@node2's password:
 ​
 Number of key(s) added: 1
 ​
 Now try logging into the machine, with:   "ssh 'User2@node2'"
 and check to make sure that only the key(s) you wanted were added.

3、登录验证成功：

说明：

1、此时 node1 上用户 User1 的私钥文件内容（id_rsa.pub）会追加到 node2 上用户 User2 的 ~/.ssh/authorized_keys 文件中：

2、还可以通过 scp 命令，将 node1 服务器上的公钥拷贝到 node2 服务器上，然后追加到 ~/.ssh/authorized_keys，

 scp ~/.ssh/id_rsa.pub User2@node2:~/

3、还可以通过 cat 命令直接追加：

 cat ~/.ssh/id_rsa.pub | ssh -P 22 User2@node2 'cat >> ~/.ssh/authorized_keys'