参考连接：
【linux】CentOS 7报错：yum命令报错 “ Cannot find a valid baseurl for repo: base/7/x86_6 ”_centos linux yum search ifconfig cannot find a val-CSDN博客
Centos7出现问题Cannot find a valid baseurl for repo: base/7/x86_64，Could not retrieve mirrorlist_centos7 cannot find a valid-CSDN博客
CentOS7.9安装Mysql5.7, 解决公钥未安装错误,设置root密码为空
参考链接CentOS7.9安装Mysql5.7, 解决公钥未安装错误,设置root密码为空_的公钥尚未安装 centos-CSDN博客