wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo
yum clean
yum makecache
Centos6更换阿里云yum源
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
# CentOS6更换
wget -O /etc/yum.repos.d/CentOS-Base.repo
# CentOS7更换
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum clean
yum makecache