启用EPEL6 yum源：
1、RHEL/CentOS/SL Linux 6.x 下安装 EPEL6 yum源：
32位系统选择：rpm -ivh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
64位系统选择：
yum install -y https://mirrors.tuna.tsinghua.edu.cn/epel/epel-release-latest-6.noarch.rpm
导入key：rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
2、RHEL/CentOS/SL Linux 7.x 下安装 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
3、阿里云yum
CentOS
1、备份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2、下载新的CentOS-Base.repo 到/etc/yum.repos.d/
CentOS 5
wget -O /etc/yum.repos.d/CentOS-ali.repo http://mirrors.aliyun.com/repo/Centos-5.repo
CentOS 6
wget -O /etc/yum.repos.d/CentOS-ali.repo http://mirrors.aliyun.com/repo/Centos-6.repo
CentOS 7
wget -O /etc/yum.repos.d/CentOS-ali.repo http://mirrors.aliyun.com/repo/Centos-7.repo