centos6버전 설치할 일이 있어서 VM에 centos6.6버전 설치 한 후 yum update할려고해보니 아래처럼 에러발생 Loaded plugins: fastestmirror, security Setting up Update Process Loading mirror speeds from cached hostfile YumRepo Error: All mirror URLs are not using ftp, http[s] or file. Eg. Invalid release/repo/arch combination/ removing mirrorlist with no valid mirrors: /var/cache/yum/x86_64/6/base/mirrorlist.txt Error: Cannot find a ..