解决GPG error: The following signatures couldn't be verified because the public key is not available

将Ubuntu的源修改为国内源：https://blog.csdn.net/zhuiqiuzhuoyue583/article/details/88777483

将Ubuntu的源修改为国内源的之后，执行

sudo apt-get update

出现问题：

GPG error: The following signatures couldn't be verified because the public key is not available

解决方法：

1.  
   sudo gpg --keyserver keyserver.ubuntu.com --recv 5523BAEEB01FA116 //(这个公钥根据提示来写的)
2.  
    
3.  
   sudo gpg --export --armor 5523BAEEB01FA116 | sudo apt-key add -

再执行下面命令，就不报错了。

sudo apt-get update