centos7 更换为aliyun的yum源

rm -f /etc/yum.repos.d/*

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

wget -O /etc/yum.repos.d/epel-7.repo http://mirrors.aliyun.com/repo/epel-7.repo

yum clean all
yum makecache

如果报错：http://mirrors.aliyun.com/centos/7Server/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

则修改CentOS-Base.repo文件，把里面的$releasever改为7