解决yum的奇怪问题，先执行以下命令

Cannot retrieve metalink for repository: fedora. Please verify its path and try again或者是
Cannot retrieve metalink for repository: epel. Please verify its path and try again解决方法
执行如下命令：
su -c "sed -i 's|^#baseurl|baseurl| ; s|^mirrorlist|#mirrorlist|' /etc/yum.repos.d/*"