啓用EPEL6 yum源：
1、RHEL/CentOS/SL Linux 6.x 下安裝 EPEL6 yum源：
32位系統選擇：rpm -ivh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
64位系統選擇：
yum install -y https://mirrors.tuna.tsinghua.edu.cn/epel/epel-release-latest-6.noarch.rpm
導入key：rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
2、RHEL/CentOS/SL Linux 7.x 下安裝 EPEL7 yum源：
http://download.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-6.noarch.rpm
http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm