CentOS，是基于 Red Hat Linux 提供的可自由使用源代码的企业级 Linux 发行版本；是一个稳定，可预测，可管理和可复制的免费企业级计算平台。
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
CentOS 6
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
CentOS 7
wget -O /etc/yum.repos.d/CentOS-Base.repo 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
# 清除缓存：
yum clean all
# 生成缓存
yum makecache
非阿里云ECS用户会出现 Couldn‘t resolve host ‘mirrors.cloud.aliyuncs.com‘ 信息，不影响使用。用户也可自行修改相关配置: eg:
sed -i -e ‘/mirrors.cloud.aliyuncs.com/d‘ -e ‘/mirrors.aliyuncs.com/d‘ /etc/yum.repos.d/CentOS-Base.repo
原文：https://www.cnblogs.com/centos-8/p/13055500.html