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
如果報錯：http://mirrors.aliyun.com/centos/7Server/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
則修改CentOS-Base.repo檔案，把裡面的$releasever改為7