【centos】CentOS配置阿里云yum源
一、备份原来的yum源，以防后续使用
cd /etc/yum.repos.d/;mkdir bak/; mv *.repo bak/
二、下载阿里云的base源
Centos6：
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-6.repo
或者：
curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-6.repo
Centos7：
wget https://mirrors.aliyun.com/repo/Centos-7.repo
或者：
curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo
Centos：8
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo
或者：
curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo
三、下载阿里云的epel源
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
四、清除缓存并生成新的缓存
yum clean all && yum makecache
生成缓存需要时间，可以直接显示当前可用yum源
yum clean all && yum repolist