One of the configured repositories failed (Unknown),and yum doesn‘t have enough cache_one of the configured repositories failed (extra p

进入到 vi 编辑界面：

vi /etc/yum.repos.d/epel.repo
ps：有vim，可以用vim

进入编辑  按 i

// 将下面的这一段代码修改为：
 
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch
 
 
// 改为：
 
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch

保存退出 vi 编辑：

 按Esc键，输入 :wq  回车