1)先安装wget
执行命令 yum install -y wget

[root@localhost ~]# yum install -y wget
  1. 查询国内镜像源

打开阿里镜像http://mirrors.aliyun.com/

CentOS7更换镜像源_镜像源
点击帮助:
CentOS7更换镜像源_清除缓存_02
3)下载CentOS 7的repo文件

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

4)更新镜像源

#清除缓存
yum clean all  
#生成缓存
yum makecache
[root@localhost ~]# yum clean all
Loaded plugins: fastestmirror
Cleaning repos: base extras updates
Cleaning up everything
Cleaning up list of fastest mirrors
[root@localhost ~]# yum makecache
Loaded plugins: fastestmirror
base                                                                                                                                                                  | 3.6 kB  00:00:00     
extras                                                                                                                                                                | 3.4 kB  00:00:00     
updates                                                                                                                                                               | 3.4 kB  00:00:00     
(1/12): base/7/x86_64/group_gz                                                                                                                                        | 155 kB  00:00:00     
(2/12): extras/7/x86_64/filelists_db                                                                                                                                  | 770 kB  00:00:02     
(3/12): extras/7/x86_64/primary_db                                                                                                                                    | 151 kB  00:00:00     
(4/12): extras/7/x86_64/other_db                                                                                                                                      | 640 kB  00:00:07     
(5/12): updates/7/x86_64/filelists_db 
.......省略