ssh-keygen的命令手冊，通過”man ssh-keygen“命令：
通過命令”ssh-keygen -t rsa“
生成之後會在用戶的根目錄生成壹個 “.ssh”的文件夾
進入“.ssh”會生成以下幾個文件
authorized_keys:存放遠程免密登錄的公鑰,主要通過這個文件記錄多臺機器的公鑰
id_rsa : 生成的私鑰文件
id_rsa.pub ：生成的公鑰文件
know_hosts : 已知的主機公鑰清單
如果希望ssh公鑰生效需滿足至少下面兩個條件：
1) .ssh目錄的權限必須是700
2) .ssh/authorized_keys文件權限必須是600
2.遠程免密登錄
原理圖：
常用以下幾種方法：
2.1 通過ssh-copy-id的方式
命令： ssh-copy-id -i ~/.ssh/id_rsa.put <romte_ip>
舉例：
[root@test .ssh]# ssh-copy-id -i ~/.ssh/id_rsa.pub 192.168.91.135
root@192.168.91.135's password:
Now try logging into the machine, with "ssh '192.168.91.135'", andcheck in:
.ssh/authorized_keys
to make sure we haven't added extra keys that you weren't expecting.
[root@test .ssh]# ssh root@192.168.91.135
Last login: Mon Oct 10 01:25:49 2016 from 192.168.91.133
[root@localhost ~]#
常見錯誤：
[root@test ~]# ssh-copy-id -i~/.ssh/id_rsa.pub 192.168.91.135
-bash: ssh-copy-id: command not found //提示命令不存在
解決辦法：yum -y installopenssh-clients
2.2 通過scp將內容寫到對方的文件中
命令：scp -p~/.ssh/id_rsa.pub root@<remote_ip>:/root/.ssh/authorized_keys
舉例：
[root@test .ssh]# scp -p ~/.ssh/id_rsa.pubroot@192.168.91.135:/root/.ssh/authorized_keys
root@192.168.91.135's password:
id_rsa.pub 100% 408 0.4KB/s 00:00
[root@test .ssh]#
[root@test .ssh]#
[root@test .ssh]#
[root@test .ssh]# ssh root@192.168.91.135
Last login: Mon Oct 10 01:27:02 2016 from 192.168.91.133
[root@localhost ~]#
也可以分為兩步操作：
$ scp ~/.ssh/id_rsa.pubroot@<remote_ip>:pub_key //將文件拷貝至遠程服務器
$ cat ~/pub_key>>~/.ssh/authorized_keys //將內容追加到authorized_keys文件中，不過要登錄遠程服務器來執行這條命令
2.3 通過Ansible實現批量免密
2.3.1 將需要做免密操作的機器hosts添加到/etc/ansible/hosts下：
[Avoid close]
192.168.91.132
192.168.91.133
192.168.91.134
2.3.2 執行命令進行免密操作
ansible<groupname> -m authorized_key -a "user=root key='{{lookup('file','/root/.ssh/id_rsa.pub') }}'" -k
示例：
[root@test sshpass-1.05]# ansible test -m authorized_key -a"user=root key='{{ lookup('file','/root/.ssh/id_rsa.pub') }}'" -k
SSH password: ----->輸入密碼
192.168.91.135 | success >> {
"changed": true,
"key": "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEArZI4kxlYuw7j1nt5ueIpTPWfGBJoZ8Mb02OJHR8yGW7A3izwT3/uhkK7RkaGavBbAlprp5bxp3i0TyNxa/apBQG5NiqhYO8YCuiGYGsQAGwZCBlNLF3gq1/18B6FV5moE/8yTbFA4dBQahdtVP PejLlSAbb5ZoGK8AtLlcRq49IENoXB99tnFVn3gMM0aX24ido1ZF9RfRWzfYF7bVsLsrIiMPmVNe5KaGL9kZ0svzoZ708yjWQQCEYWp0m+sODbtGPC34HMGAHjFlsC/SJffLuT/ug/hhCJUYeExHIkJF8OyvfC6DeF7ArI6zdKER7D8M0SMWQmpKUltj2nltuv3w== root@localhost.localdomain",
"key_options": null,
"keyfile": "/root/.ssh/authorized_keys",
"manage_dir": true,
"path": null,
"state": "present",
"unique": false,
"user": "root"
}
[root@test sshpass-1.05]#
2.4 手工復制粘貼的方式
將本地id_rsa.pub文件的內容拷貝至遠程服務器的~/.ssh/authorized_keys文件中