你好，我遇到了一个问题，当我在 Centos 7 中输入“yum update”时，系统会显示下一个错误
从缓存的主机文件加载镜像速度
其中一个配置的存储库失败（未知），yum 没有足够的缓存数据来继续。此时 yum 唯一能安全做的事情就是失败。有几种方法可以“修复”此问题：
1. Contact the upstream for the repository and get them to fix the problem.
2. Reconfigure the baseurl/etc. for the repository, to point to a working
upstream. This is most often useful if you are using a newer
distribution release than is supported by the repository (and the
packages for the previous distribution release still work).
3. Run the command with the repository temporarily disabled
yum --disablerepo=<repoid> ...
4. Disable the repository permanently, so yum won't use it by default. Yum
will then just ignore the repository until you permanently enable it
again or use --enablerepo for temporary usage:
yum-config-manager --disable <repoid>
or
subscription-manager repos --disable=<repoid>
5. Configure the failing repository to be skipped, if it is unavailable.
Note that yum will try to contact the repo. when it runs most commands,
so will have to try and fail each time (and thus. yum will be be much
slower). If it is a very temporary problem though, this is often a nice
compromise:
yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=true
无法找到 repo 的有效 baseurl：commercial-addons/x86_64
我尝试使用 ONBOOT=no 命令，然后使用 dhclient，但问题没有得到解决；如果有人能帮助我，我将不胜感激