CentOS上安装EPEL源

　　EPEL (Extra Packages for Enterprise Linux)是基于Fedora的一个项目，为“红帽系”的操作系统提供额外的软件包，适用于RHEL、CentOS和Scientific Linux.
　　如何安装:

Centos7 64位：
rpm -ivh http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm
Centos6 32位：
rpm -ivh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
centos6 64位：
rpm -ivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
centos5 32位：
rpm -ivh http://dl.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm
centos5 64位：
rpm -ivh http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm

可能遇到异常：

Retrieving http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
error: skipping http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm - transfer failed

可以先下载下来，再安装：

wget http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
rpm -ivh epel-release-6-5.noarch.rpm

还可能有这异常：

Error: Cannotretrieve metalink for repository: epel. Please verify its path and try again

解决办法：

vim /etc/yum.repos.d/epel.repo

去掉[epel]下的baseurl前的#号，mirrorlist前添加#号。