配置阿里yum源（这个很重要）：https://developer.aliyun.com/article/1480470

1.备份系统自带yum源配置文件

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

2.下载ailiyun的yum源配置文件

2.1 CentOS7

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

2.2 CentOS6

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

2.3 重新生成缓存

yum makecache