yum自动补全
yum install bash-completion -y
阿里云官方镜像站
https://developer.aliyun.com/mirror/
添加yum软件仓库
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo
或者
sudo yum-config-manager --add-repo=http://classroom.example.com/