前言：因为笔者有两个开发环境，一个是Ubuntu16.04的虚拟机，一个是Linux Mint 18的物理机，然后Mint的好弄，基本就是按照教程来就行了，就是这个Ubuntu的有点逻辑问题，什么问题，下面说。
第一步、肯定是生成id_rsa.pub啦
Github官方的做法是这样的
ssh-keygen -t rsa -b 4096 -C "you_email@mail.com"
但是如果你这样在Ubuntu上做了，后面你test链接的时候就会
code@code-VirtualBox:~/Downloads$ ssh -T git@github.com
The authenticity of host 'github.com (192.30.253.113)' can't be established.
RSA key fingerprint is SHA256:------------------------.
Are you sure you want to continue connecting (yes/no)? yes
Failed to add the host to the list of known hosts (/home/code/.ssh/known_hosts).
Load key "/home/code/.ssh/id_rsa": Permission denied
Permission denied (publickey).
没错，看到了没有，Permission denied
然后又看到这个P D， 加sudo
code@code-VirtualBox:~/Downloads$ sudo ssh -T git@github.com
Permission denied (publickey).
为什么会这样呢？
因为第一个是因为你没有权限去用/home/code/.ssh/下的pub公钥
加了sudo之后，你变root了，现在调用的是/root/.ssh/选的pub公钥了
所以这里有个逻辑漏洞。
第二步、解决
直接用/root/.ssh/下的公钥
先生成
code@code-VirtualBox:~/.ssh$ sudo ssh-keygen -t rsa -b 4096 -C "xxx@yyy.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
/root/.ssh/id_rsa already exists.
Overwrite (y/n)? y
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:-----------------------xxx@yyy.com
The key's randomart image is:
+---[RSA 4096]----+
......
+----[SHA256]-----+
然后你是进不去/root/.ssh/的
方法就是把这pub铐出来
code@code-VirtualBox:~/.ssh$ cd /root/.ssh/
bash: cd: /root/.ssh/: Permission denied
我是把它铐到Downloads目录下
code@code-VirtualBox:~/.ssh$ sudo cp /root/.ssh/id_rsa.pub /home/code/Downloads/
然后用gedit打开，复制到github上的ssh-key哪里
然后测试一下
code@code-VirtualBox:~/.ssh$ sudo ssh -T git@github.com
Hi SuperSuperSuperSuper5! You've successfully authenticated, but GitHub does not provide shell access.
说明我们链接上了，测试成功，以后push代码的时候，加上sudo就行了。