系统：centos7.8
问题:
root@dev Downloads]# yum install alien
Loaded plugins: fastestmirror, langpacks, product-id, search-disabled-repos, subscription-manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
Loading mirror speeds from cached hostfile
* base: ftp.
* extras: ftp.
* updates: ftp.
No package alien available.
Error: Nothing to do
解决方式：yum install epel-release
再重试就ok了
