我刚刚安装了新的虚拟机，当我运行 yum update 命令时出现以下错误 [root@localhost ~]# yum 更新 加载的插件：fastestmirror 从缓存的主机文件加载镜像速度 无法检索镜像列表 http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock 错误是 14: curl#6 - “无法解析主机：mirrorlist.centos.org；未知错误”
配置的存储库之一失败（未知）， 并且 yum 没有足够的缓存数据来继续。此时唯一 yum 可以做的安全事情就是失败。有几种方法可以“解决”这个问题：
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
找不到 repo 的有效 baseurl：base/7/x86_64
我想更新它，这样我就可以配置似乎缺少的东西。