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[操作系统]Linux下实现免密登录


1.Linux下生成密钥 

  ssh-keygen的命令手册,通过”man ssh-keygen“命令:

  

  通过命令”ssh-keygen -t rsa“

  

  生成之后会在用户的根目录生成一个 “.ssh”的文件夹

  

  进入“.ssh”会生成以下几个文件

  

  authorized_keys:存放远程免密登录的公钥,主要通过这个文件记录多台机器的公钥
  id_rsa : 生成的私钥文件
  id_rsa.pub : 生成的公钥文件
  know_hosts : 已知的主机公钥清单

    如果希望ssh公钥生效需满足至少下面两个条件:

      1) .ssh目录的权限必须是700 
      2) .ssh/authorized_keys文件权限必须是600

2.远程免密登录

  原理图:

    

   常用以下几种方法:

    2.1 通过ssh-copy-id的方式

    命令: ssh-copy-id -i ~/.ssh/id_rsa.put <romte_ip>

    举例:      

[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'", and check 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 ~]#

    常见错误:

      [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

      解决办法:yum -y install openssh-clients

 

    2.2 通过scp将内容写到对方的文件中

      命令:scp -p ~/.ssh/id_rsa.pub root@<remote_ip>:/root/.ssh/authorized_keys

      举例:

[root@test .ssh]# scp -p ~/.ssh/id_rsa.pub root@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 ~]#

 

      也可以分为两步操作:

$ scp ~/.ssh/id_rsa.pub root@<remote_ip>:pub_key       //将文件拷贝至远程服务器
$ cat ~/pub_key >>~/.ssh/authorized_keys                     //将内容追加到authorized_keys文件中, 不过要登录远程服务器来执行这条命令

    2.3 通过Ansible实现批量免密

2.3.1 将需要做免密操作的机器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 执行命令进行免密操作

  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: ----->输入密码
  192.168.91.135 | success >> {
  "changed": true,
  "key": "ssh-rsa     AAAAB3NzaC1yc2EAAAABIwAAAQEArZI4kxlYuw7j1nt5ueIpTPWfGBJoZ8Mb02OJHR8yGW7A3izwT3/uhkK7RkaGavBbAlprp5bxp3i0TyNxa/apBQG5NiqhYO8YCuiGYGsQAGwZCBlNLF3gq1/18B6FV5moE/8yTbFA4dBQahdtVP  PejLlSAbb5ZoGK8AtLlcRq49IENoXB99tnFVn3gMM0aX24ido1ZF9RfRWzfYF7bVsLsrIiMPmVNe5KaGL9kZ0svzoZ708yjWQQCEYWp0m+sODbtGPC34HMGAHjFlsC/SJffLuT/ug/hhCJUYeExHIkJF8OyvfC6DeF7ArI6zdKER7D8M0SM  WQmpKUltj2nltuv3w== 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 手工复制粘贴的方式

  将本地id_rsa.pub文件的内容拷贝至远程服务器的~/.ssh/authorized_keys文件中