centOS切换yum源为国内阿里云

cd /etc/yum.repos.d
mv ./CentOS-Base.repo ./CentOS-Base.repo.bak
mv ./epel-7.repo ./epel-7.repo.bak
wget http://mirrors.aliyun.com/repo/Centos-7.repo
wget https://mirrors.aliyun.com/repo/epel-7.repo
yum clean all
yum makecache