https://blog.csdn.net/sinat_34080511/article/details/116707749?ops_request_misc=&request_id=&biz_id=102&utm_term=gcc%E5%8D%87%E7%BA%A7&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduweb~default-0-116707749.nonecase&spm=1018.2226.3001.4449
yum源配置的什么，如果是默认的话，是否能连接外网？
