yum安装时出现：Cannot retrieve metalink for repository: epel. Please verify its path and try again
　　在CentOS 6.3 x86_64下安装php-mcrypt的时候出现了问题：Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again，需要安装epel源。
　　解决方法： 一句话：把/etc/yum.repos.d/epel.repo，文件第3行注释去掉，把第四行注释掉。具体如下：
　　打开/etc/yum.repos.d/epel.repo，将
　　[epel]
　　name=Extra Packages for Enterprise Linux 6 - $basearch
　　#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
　　mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
　　修改为
　　[epel]
　　name=Extra Packages for Enterprise Linux 6 - $basearch
　　baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
　　#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
　　再清理源，重新安装
　　yum clean all
　　yum install -y 需要的包