linux修改yum源为阿里云

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