我已经在 hyper-v 上成功安装了 CentOS 7，但是当我尝试使用 yum update 进行更新或尝试使用yum命令进行安装时，出现以下错误：
Loaded plugins: fastestmirror, langpacks Could not retrieve mirrorlist
http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock
error was 12: Timeout on
http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock:
(28, 'Resolving timed out after 30425 milliseconds')
One of the configured repositories failed (Unknown), and yum doesn't
have enough cached data to continue. At this point the only safe
thing yum can do is fail. There are a few ways to work "fix" this:
1. Contact the upstream for the repository and get them to …