一、情景

公司剛上幾臺Linux，現(xiàn)在要把主機之間都能遠(yuǎn)程ssh免密碼登陸。

二、原理
很簡單，使用ssh-keygen 在主機A上生成private和public密鑰，將生成的public密鑰拷貝到遠(yuǎn)程機器主機B上后,就可以使用ssh命令無需密碼登錄到另外一臺機器主機B上。

三、步驟

主機A：

1、 生成公鑰和私鑰文件id_rsa和id_rsa.pub （敲3下回車即可）
[root@bogon ~]# 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):
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:
67:da:0d:79:e0:d6:2b:cd:7d:22:af:51:7e:9c:75:fe root@bogon
The key's randomart image is:
+--[ RSA 2048]----+
| |
| |
| . |
| . + |
| S B o . o|
| * * = o+|
| . o B +.=|
| . + +.|
| ... E|
+-----------------+

2、ssh-cop-id命令會將指定的公鑰文件復(fù)制到遠(yuǎn)程計算機

[root@bogon ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@10.1.250.166
The authenticity of host '10.1.250.166 (10.1.250.166)' can't be established.
RSA key fingerprint is c8:9d:6d:92:55:77:3d:3e:af:f5:cb:18:80:5a:47:93.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '10.1.250.166' (RSA) to the list of known hosts.
reverse mapping checking getaddrinfo for bogon [10.1.250.166] failed - POSSIBLE BREAK-IN ATTEMPT!
root@10.1.250.166's password: <主機B的登陸密碼>
Now try logging into the machine, with "ssh 'root@10.1.250.166'", and check in:

.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

3、然后ssh登陸主機B驗證是否需要密碼

[root@localhost ~]# ssh 10.1.250.166
reverse mapping checking getaddrinfo for bogon [10.1.250.166] failed - POSSIBLE BREAK-IN ATTEMPT!
Last login: Wed Oct 21 10:05:39 2015 from 10.1.250.141
[root@bogon ~]#

4、登陸成功后，我們需要在主機B也做下以上3步，這樣就可以相互免密碼ssh登陸。（如果有多臺主機，每臺主機都做下相同操作，以方便以后管理）。

5、權(quán)限問題
建議用其他用戶做ssh登陸的話，調(diào)整目錄文件權(quán)限
設(shè)置authorized_keys權(quán)限

chmod 644 authorized_keys

設(shè)置.ssh目錄權(quán)限

chmod 700 -R .ssh

6、要保證.ssh和authorized_keys都只有用戶自己有寫權(quán)限。否則驗證無效。

本文出自 “好大的刀” 博客

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