学习记录：
工作用到redhat 7.4 与redhat7.6 得系统，安装一些软件需要使用得网络源，这里记录一下网络源。
cat /etc/yum.repos.d/test.repo
[base]
name=CentOS-$releasever - Base
baseurl=https://mirrors.aliyun.com/centos/7/os/x86_64/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/7/os/x86_64/RPM-GPG-KEY-CentOS-7
[updates]
name=CentOS-$releasever - Updates
baseurl=https://mirrors.aliyun.com/centos/7/updates/x86_64/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/7/os/x86_64/RPM-GPG-KEY-CentOS-7
[extras]
name=CentOS-$releasever - Extras
baseurl=https://mirrors.aliyun.com/centos/7/extras//x86_64/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/7/os/x86_64/RPM-GPG-KEY-CentOS-7
[centosplus]
name=CentOS-$releasever - Plus
baseurl=https://mirrors.aliyun.com/centos/7/centosplus//x86_64/
gpgcheck=1
enabled=1
gpgkey=https://mirrors.aliyun.com/centos/7/os/x86_64/RPM-GPG-KEY-CentOS-7
yum clean all
yum makecache
yum repolist