原理：

  • 机器1生成密钥对并将公钥发给机器2，机器2将公钥保存。
  • 机器1要登录机器2时，机器2生成随机字符串并用机器1的公钥加密后，发给机器1。
  • 机器1用私钥将其解密后发回给机器2，验证成功后登录

    通俗来说：

    验证成功的本质，将57机器的公钥id_rsa.pub的内容传递到 58机器中的authorized_keys文件中。57机器要登录58机器时时，58机器用机器57的公钥加密生成的随机字符串后，发给57机器，57机器用私钥将其解密后发回给58机器，验证成功后登录

普通登录： ssh root@10.80.34.59

  2. [root@kylin236 ~/.ssh 10:54:13]# ssh root@10.80.34.59
  3. root@10.80.34.59's password:
  4. Last login: Mon Dec 21 09:54:21 2020 from 10.80.26.72

1.两台机器互相免密登录

ip: 10.80.34.57
ip: 10.80.34.58

在57机器中输入 sshkey-gen
生成公钥id_rsa.pub 和私钥id_rsa

57免密码登录58：

  1. [root@kylin236 ~ 09:43:58]#  ssh-keygen
  2. Generating public/private rsa key pair.
  3. Enter file in which to save the key (/root/.ssh/id_rsa):
  4. Enter passphrase (empty for no passphrase):
  5. Enter same passphrase again:
  6. Your identification has been saved in /root/.ssh/id_rsa.
  7. Your public key has been saved in /root/.ssh/id_rsa.pub.
  8. The key fingerprint is:
  9. SHA256:Pu76S3gVip7XlTU8dWgE/J5mMpkHOQAgbZJshza71/M root@kylin236
  10. The key's randomart image is:
  11. +---[RSA 2048]----+
  12. |   ..+.... ..o..o|
  13. |    O.+   . ..o..|
  14. |   o *    .. +=  |
  15. |    .  . . .+o.o |
  16. |     ...S . o* . |
  17. |    ...+oo .= *  |
  18. |     .+ *o.  *   |
  19. |       = .E      |
  20. |      .+=.       |
  21. +----[SHA256]-----+
  22. [root@kylin236 ~ 09:45:50]# cd .ssh
  23. [root@kylin236 ~/.ssh 09:46:10]# ls
  24. id_rsa  id_rsa.pub  known_hosts
  25. [root@kylin236 ~/.ssh 09:46:11]# ssh-copy-id 10.80.34.58
  26. [root@kylin236 ~ 09:54:46]# ssh-copy-id 10.80.34.58
  27. /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
  28. /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
  29. /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
  30. root@10.80.34.58's password:
  32. Number of key(s) added: 1
  34. Now try logging into the machine, with:   "ssh '10.80.34.58'"
  35. and check to make sure that only the key(s) you wanted were added.
  37. [root@kylin236 ~ 09:56:52]# ssh 10.80.34.58
  38. Last login: Mon Dec 21 01:52:55 2020 from 10.80.26.72
  39. [root@localhost ~]#  等待输入超时：自动登出
  40. Connection to 10.80.34.58 closed.

58免密码登陆57：

重复一次
ssh-keygen
ssh-copy-id 10.80.34.57

  1. [root@localhost ~]# ssh-keygen
  2. Generating public/private rsa key pair.
  3. Enter file in which to save the key (/root/.ssh/id_rsa):
  4. Enter passphrase (empty for no passphrase):
  5. Enter same passphrase again:
  6. Your identification has been saved in /root/.ssh/id_rsa.
  7. Your public key has been saved in /root/.ssh/id_rsa.pub.
  8. The key fingerprint is:
  9. SHA256:pm32k3GZk7Fray0k6KpgoKG0KcN2m+WhxlL7EXtn00s root@localhost.localdomain
  10. The key's randomart image is:
  11. +---[RSA 2048]----+
  12. |                 |
  13. |                 |
  14. |                 |
  15. |            .    |
  16. |o.   .  S.   *   |
  17. |=oo.  o+. + O    |
  18. |===..=.o++ E +   |
  19. |o+.=* +o+.= * .  |
  20. |  o+o+..  .=.o   |
  21. +----[SHA256]-----+
  22. [root@localhost ~]# ssh-copy-id 10.80.34.57
  23. /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa                                                                                                                                                             .pub"
  24. The authenticity of host '10.80.34.57 (10.80.34.57)' can't be established.
  25. ECDSA key fingerprint is SHA256:mx6pcAt7Ux4o5sZqKNnAdTIwQ16P8vke0O2VKkjEFJ0.
  26. ECDSA key fingerprint is MD5:4d:20:6e:a2:55:2f:13:34:4b:09:e9:69:c5:53:06:f2.
  27. Are you sure you want to continue connecting (yes/no)? yes
  28. /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter                                                                                                                                                              out any that are already installed
  29. /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompt                                                                                                                                                             ed now it is to install the new keys
  30. root@10.80.34.57's password:
  32. Number of key(s) added: 1
  34. Now try logging into the machine, with:   "ssh '10.80.34.57'"
  35. and check to make sure that only the key(s) you wanted were added.
  37. [root@localhost ~]# ssh 10.80.34.57
  38. Last login: Mon Dec 21 09:43:11 2020 from 10.80.26.72
  39. [root@kylin236 ~ 10:53:36]# cd .ssh

此时57和58机器的authorized_keys，id_rsa.pub文件互为对方的文件的内容

  1. 58的authorized_keys
  2. [root@localhost .ssh]# cat authorized_keys
  3. ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCVs5HvdKM8Ui4kseUz4V3mUquMlCTPfq5xexD8kJmYe4w9CiWtjeuerhMRPEOCPmOwHUBO0k/YGvTNDe6Non0qhWpXo06foRpE/E62p+AsOh2xX46IXrB24QRVFQJWBoo7aYe6fbP27v4KGXH5dSMz0RXnU6Tb8JDmuJB/h7A3ewsbyYt8kHIH1A0g+45UagMppg/nZA0WEy21jKEVCHPnjB0X2cLgz/ERE6P8f0Vy2ClKIdCGCmx70IF7fA/bQfrB+dYQ449kbGfOkVnu2joNJPY7iE8wl1F9VZb9/gJf248Xh4+F60HjBeN5ZWaMpGyujBArVesF0Gic2iAPSNFv root@kylin236
  6. 57的id_rsa.pub
  7. [root@kylin236 ~/.ssh 11:05:47]# cat  id_rsa.pub
  8. ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCVs5HvdKM8Ui4kseUz4V3mUquMlCTPfq5xexD8kJmYe4w9CiWtjeuerhMRPEOCPmOwHUBO0k/YGvTNDe6Non0qhWpXo06foRpE/E62p+AsOh2xX46IXrB24QRVFQJWBoo7aYe6fbP27v4KGXH5dSMz0RXnU6Tb8JDmuJB/h7A3ewsbyYt8kHIH1A0g+45UagMppg/nZA0WEy21jKEVCHPnjB0X2cLgz/ERE6P8f0Vy2ClKIdCGCmx70IF7fA/bQfrB+dYQ449kbGfOkVnu2joNJPY7iE8wl1F9VZb9/gJf248Xh4+F60HjBeN5ZWaMpGyujBArVesF0Gic2iAPSNFv root@kylin236
  1. 57的authorized_keys
  2. [root@kylin236 ~/.ssh 11:18:12]# cat authorized_keys
  3. ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDAEVilSZN3YsDzDsmX3RVM/UuRfRPzFrYTrFu2kBcrz7XemorYEuhgEEEaQwKmaNTIWNEv5bfLx9ICHQXbhnm7kuN6kK2jOozgn4ibxzlP4a5i7PqitbxkSc0lZNhZ4OFJNOW8iL2aNVvlI+2eYjyDEdeXnFI8ocw525GRMMwQKsCHwtdtmyTGH8CNoXffw0CMM8JgWQ9xhaHNY0Iy2cFc5J39D1f+gbCHfc6GHdKXGVZBM8nuIDmM1Selpc+YRzX2zNkmPTdCdRacO7UhD2rAOWksE+SRx4Ay9RvKLrOYPKotx/Pw53ieIIRmUry0LQlRKAKKIsd5SYUqVI38fk7V root@localhost.localdomain
  6. 58的id_rsa.pub
  7. [root@localhost .ssh]# cat id_rsa.pub
  8. ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDAEVilSZN3YsDzDsmX3RVM/UuRfRPzFrYTrFu2kBcrz7XemorYEuhgEEEaQwKmaNTIWNEv5bfLx9ICHQXbhnm7kuN6kK2jOozgn4ibxzlP4a5i7PqitbxkSc0lZNhZ4OFJNOW8iL2aNVvlI+2eYjyDEdeXnFI8ocw525GRMMwQKsCHwtdtmyTGH8CNoXffw0CMM8JgWQ9xhaHNY0Iy2cFc5J39D1f+gbCHfc6GHdKXGVZBM8nuIDmM1Selpc+YRzX2zNkmPTdCdRacO7UhD2rAOWksE+SRx4Ay9RvKLrOYPKotx/Pw53ieIIRmUry0LQlRKAKKIsd5SYUqVI38fk7V root@localhost.localdomain

此时58,58机器可以互相免密登录，互相有了对方的公钥内容。

2.一对多台机器免密登录：

机器IP
192.168.145.235 10.80.34.58
192.168.145.236 10.80.34.57
192.168.145.237 10.80.34.59
192.168.145.239 10.80.34.55
192.168.145.238 10.80.34.54
以一台机器(57机器)为固定机器形成一对多的免密登录的模式
1. 编辑57机器中的hosts文件，保存后不用重启

  1. [root@kylin236 ~ 14:49:35]# cat /etc/hosts
  2. 10.80.34.58  h58
  3. 10.80.34.57  h57
  4. 10.80.34.59  h59
  5. 10.80.34.55  h55

2.在四台机器都执行 ssh-keygen
3.在57机器上执行 ，把自己的公钥内容都复制到其他机器上
ssh-copy-id h58
ssh-copy-id h59
ssh-copy-id h55
4.此时可以看到另外三台机器的authorized_keys都是236的id_rsa.pub的内容

  1. [root@kylin237 .ssh]# cat authorized_keys
  2. ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCVs5HvdKM8Ui4kseUz4V3mUquMlCTPfq5xexD8kJmYe4w9CiWtjeuerhMRPEOCPmOwHUBO0k/YGvTNDe6Non0qhWpXo06foRpE/E62p+AsOh2xX46IXrB24QRVFQJWBoo7aYe6fbP27v4KGXH5dSMz0RXnU6Tb8JDmuJB/h7A3ewsbyYt8kHIH1A0g+45UagMppg/nZA0WEy21jKEVCHPnjB0X2cLgz/ERE6P8f0Vy2ClKIdCGCmx70IF7fA/bQfrB+dYQ449kbGfOkVnu2joNJPY7iE8wl1F9VZb9/gJf248Xh4+F60HjBeN5ZWaMpGyujBArVesF0Gic2iAPSNFv root@kylin236
  4. [root@kylin236 ~/.ssh 15:56:58]# cat id_rsa.pub
  5. ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCVs5HvdKM8Ui4kseUz4V3mUquMlCTPfq5xexD8kJmYe4w9CiWtjeuerhMRPEOCPmOwHUBO0k/YGvTNDe6Non0qhWpXo06foRpE/E62p+AsOh2xX46IXrB24QRVFQJWBoo7aYe6fbP27v4KGXH5dSMz0RXnU6Tb8JDmuJB/h7A3ewsbyYt8kHIH1A0g+45UagMppg/nZA0WEy21jKEVCHPnjB0X2cLgz/ERE6P8f0Vy2ClKIdCGCmx70IF7fA/bQfrB+dYQ449kbGfOkVnu2joNJPY7iE8wl1F9VZb9/gJf248Xh4+F60HjBeN5ZWaMpGyujBArVesF0Gic2iAPSNFv root@kylin236

此时57可以免密登录55,58,59的机器了。
如果需要互相登录的话，再重复操作把自己的公钥的内容放进别人的authorized_keys中就可以了。
但如果机器台数多的话，这个办法不是好办法。