更换CentOS7的下载源为阿里云

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-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo[/code] 
CentOS 6
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo[/code] 
CentOS 7
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo[/code] 
3、之后运行 yum clean all, yum makecache 生成缓存
 http://mirrors.aliyun.com/help/centos 
参考文章：http://www.centoscn.com/CentOS/config/2015/0525/5524.html

1、备份(如有配置其他epel源)
mv /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel.repo.backup


mv /etc/yum.repos.d/epel-testing.repo /etc/yum.repos.d/epel-testing.repo.backup


2、下载新repo 到/etc/yum.repos.d/
epel(RHEL 7)
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo


epel(RHEL 6)
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-6.repo


epel(RHEL 5)
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-5.repo[/code]