下载了emqx-5.7.2-el8-amd64.rpm在centos8上安装，服务器没有联外网安装失败：
[root@localhost 下载]# sudo yum install emqx-5.7.2-el8-amd64.rpm -y
CentOS Linux 8 - AppStream 0.0 B/s | 0 B 04:00
Errors during downloading metadata for repository ‘appstream’:
- Curl error (6): Couldn’t resolve host name for http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock [Could not resolve host: mirrorlist.centos.org]
请问服务器必须联网吗？谢谢。