当使用带有 Centos6 映像的 VirtualBox 时，我无法再执行 yum udpate，我在互联网上查了一下，看起来 Centos6 已被弃用。
[root@centos69 ~]# yum makecache
Failed to set locale, defaulting to C
Loaded plugins: fastestmirror, refresh-packagekit, security
Determining fastest mirrors
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 valid baseurl for repo: base
[root@centos69 ~]# yum update
Failed to set locale, defaulting to C
Loaded plugins: fastestmirror, refresh-packagekit, security
Setting up Update Process …