mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo or curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
1 yum clean all 2 yum makecache 3 yum update
可能会出现 Couldn‘t resolve host ‘mirrors.cloud.aliyuncs.com‘ 信息，不影响使用。可自行修改相关配置
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/poloyy/p/12186756.html