在安装mysql8.0的存储库后，执行apt update的时候会出现报错：

Err:1 http://repo.mysql.com/apt/ubuntu bionic InRelease                                                                                                  
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C

root@ubuntu18:~# apt update
Get:1 http://repo.mysql.com/apt/ubuntu bionic InRelease [20.0 kB]                                                                                           
Hit:2 http://security.ubuntu.com/ubuntu bionic-security InRelease                                                                                           
Err:1 http://repo.mysql.com/apt/ubuntu bionic InRelease                                                                                                  
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C
Hit:3 https://repo.zabbix.com/zabbix-agent2-plugins/1/ubuntu bionic InRelease                                                      
Hit:4 https://repo.zabbix.com/zabbix/6.0/ubuntu bionic InRelease                                          
Hit:5 http://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic InRelease                   
Hit:6 http://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic-updates InRelease
Hit:7 http://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic-backports InRelease
Reading package lists... Done
W: GPG error: http://repo.mysql.com/apt/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C
E: The repository 'http://repo.mysql.com/apt/ubuntu bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

我们看报错有key的id为；B7B3B788A8D3785C

期间试过很多方式都拉取不下来，最终找到解决方法为：手动去下载key文件并添加到Mysql的存储库中：

复制邮箱打开网站：http://keyserver.ubuntu.com/

在search里面输入：[email protected]

进入后，按键盘的ctrl+f：输入B7B3B788A8D3785C

然后找到B7B3B788A8D3785C文件进行下载

然后在自己电脑下载目录找到那个文件，然后右击以记事本方式打开查看内容，复制全部内容：

再去到服务器中添加key：

vim mysql_gpgkey     //打开文件，然后将刚刚复制的key内容粘贴到里面
sudo apt-key add mysql_gpgkey     //添加key

添加完后，去查看一下有没有添加成功！：

最后再去执行

apt-get update

添加mysql8.0的key成功！