Linux免密登录

在开发中我们每次ssh到linux服务器都需要输入密码，似乎有点麻烦。有没有什么办法？

1. 在机器A上生成一对公私钥
2. A将公钥拷贝给B，在B中重命名为authorized_keys（放在当前用户目录下的.ssh目录下）
3. A向B发送一个登录链接请求
4. B得到A的登录请求信息后，在authorized_keys中查找，如果有相应的用户名和IP，则随机生成一个字符串string_text，并且使用A的公钥加密，随后发送给A
5. A接收到B发送过来的消息后，使用自己的私钥解密，然后将解密后的字符串发送给B
6. B接收到A解密后的字符串，检查是否与string_text一致，如果一致则允许免密登录

 ssh-keygen -t rsa 

[root@localhost ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Created directory '/root/.ssh'.
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:
SHA256:ZjXg+lrUvwGd0KzMN+la0BMAZBRnwR+kYvrllZcl4Q8 root@localhost.localdomain
The key's randomart image is:
+---[RSA 2048]----+
|       oB+=o. .  |
|       o +.=.. . |
|        + =.+.E .|
|       + * *.= * |
|      o S O @ o .|
|       * o B +   |
|        + . =    |
|       o   o o   |
|      .   . .    |
+----[SHA256]-----+

[root@localhost ~]# cd /root/.ssh/
[root@localhost .ssh]# ll
总用量 8
-rw-------. 1 root root 1675 5月   7 07:34 id_rsa
-rw-r--r--. 1 root root  408 5月   7 07:34 id_rsa.pub
[root@localhost .ssh]# 

免密登录的公钥统一放在目标服务器该文件：/root/.ssh/authorized_keys中，文件不存在自行创建。注意：多个公钥注意换行。

拷贝的方式有多种

1.手动拷贝

2.使用 ssh-copy-id方式

[root@localhost .ssh]# ssh-copy-id -i  /root/.ssh/id_rsa.pub root@192.168.9.131
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
^C
[root@localhost .ssh]# ssh-copy-id -i  /root/.ssh/id_rsa.pub root@192.168.1.131
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host '192.168.1.131 (192.168.1.131)' can't be established.
ECDSA key fingerprint is SHA256:EpxAt5y1VDhmCCzkoYFE1ekn1+ZkGwY3fQ7FUybvuno.
ECDSA key fingerprint is MD5:4a:06:cb:1e:7d:c1:6b:f4:41:80:fb:6d:7c:b3:f5:a2.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.1.131's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@192.168.1.131'"
and check to make sure that only the key(s) you wanted were added.

执行 ssh 如果没有提示输入密码直接登录成功，表示已经配置好免密登录了。

root@localhost .ssh]# ssh root@192.168.1.131

Last login: Sat May 7 07:22:58 2022 from 192.168.1.1

[root@localhost ~]# 

我们可以在远程该文件(/root/.ssh/authorized_keys )中查看公钥。

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