[Linux] yum 실행 안될 때 cannot find a valid baseurl for repo

cannot find a valid baseurl for repo base/7/x86_64 Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was 14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 알 수 없는 오류" One of the configured repositories failed (Unknown), and yum doesn't have enough cached data to continue.

At this point the only safe thing yum can do is fail. The.....