Linux免密登录

一、生成免密登录公钥

ssh-keygen -t rsa

如下:

[root@VM-0-9-centos /]# 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:
SHA256:ZyZSw/Ciok0MqO1My3qgo9K9ONQBxkEkz8tymflz82Q root@VM-0-9-centos
The key's randomart image is:
+---[RSA 2048]----+
|.++.  .          |
|.++    +         |
|o.o.  . =        |
|.= =.. o .       |
|o &.... S +      |
|.@.+.  . =       |
|o+*.o o E        |
|+.+..o =         |
|=o....  .        |
+----[SHA256]-----+

注意：如果每生成过此公钥，只需一路回车即可。

二、查看公钥

公钥的路径：

Enter file in which to save the key (/root/.ssh/id_rsa):

即：/root/.ssh

[root@VM-0-9-centos /]# cd /root/.ssh/
[root@VM-0-9-centos .ssh]# ls
authorized_keys  id_rsa  id_rsa.pub
[root@VM-0-9-centos .ssh]#

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

三、实现远程免密登录

在本地（或服务器A）上实现免密登录服务器B，需要将本地（或服务器A）的公钥（/root/.ssh/id_rsa.pub文件内容）配置到服务器B的/root/.ssh/authorized_keys里即可，多个公钥注意换行。

四、配置方式

4.1 通过ssh-copy-id的方式

ssh-copy-id -i ~/.ssh/id_rsa.pub <username@romte_ip>

如下：

liumeng@liumengdeMacBook-Pro .ssh % ssh-copy-id -i ~/.ssh/id_rsa.pub root@106.53.***.***
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/Users/liumeng/.ssh/id_rsa.pub"
/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@106.53.***.***'s password:

Number of key(s) added:        1

Now try logging into the machine, with:   "ssh 'root@106.53.***.***'"
and check to make sure that only the key(s) you wanted were added.

4.2 SCP方式

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

如下：

liumeng@liumengdeMacBook-Pro .ssh % scp -P 22 ~/.ssh/id_rsa.pub root@106.53.***.***:/root/.ssh/authorized_keys
root@106.53.***.***'s password:
id_rsa.pub                                                                                                                                             100%  588     7.8KB/s   00:00
liumeng@liumengdeMacBook-Pro .ssh %

4.3 通过Ansible实现批量免密

将需要做免密操作的机器hosts添加到/etc/ansible/hosts下

4.4 手动复制粘贴

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。

结束！