1. 备份源镜像

sudo cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak

2. 下载国内镜像阿里云

如果没有wget可以用curl 代替

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

清华大学

sudo wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.tuna.tsinghua.edu.cn/repo/Centos-7.repo

网易

sudo wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo

中科大源

sudo wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.ustc.edu.cn/centos/7/os/x86_64/

刷新yum

sudo yum clean all
sudo yum makecache