CentOS更换yum源

1. 备份

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

2. 下载源文件

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

3. 生成缓存

yum clean all
yum makecache