查看centos 系統是否有yum源

以下命令行可以獲取當前系統有效的repolist，舉例：

$ yum repolist

Loaded plugins: fastestmirror, langpacks

Loading mirror speeds from cached hostfile

* base: mirrors.pubyun.com

* extras: mirrors.pubyun.com

* updates: mirrors.pubyun.com

repo id repo name status

!base/7/x86_64 CentOS-7 - Base 9,007

!extras/7/x86_64 CentOS-7 - Extras 265

!updates/7/x86_64 CentOS-7 - Updates 1,401

repolist: 10,673