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
