报错：yum install 安装时报yum doesn't have enough cached data to continue

yum install 安装时报错

One of the configured repositories failed (未知),
and yum doesn’t have enough cached data to continue. At this point the only
safe thing yum can do is fail. There are a few ways to work “fix” this:

• 详细信息：

  [root@ec-cache ~]# yum install gcc
  已加载插件：fastestmirror
  base                                                                                                                                                      | 3.6 kB  00:00:00
  
  
   One of the configured repositories failed (未知),
   and yum doesn't have enough cached data to continue. At this point the only
   safe thing yum can do is fail. There are a few ways to work "fix" this:
  
       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. Disable the repository, 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>
  
       4. 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
  
  Cannot retrieve metalink for repository: epel/x86_64. Please verify its path and try again
  

• 原因：
  虚拟机没有联网…，低级错误

• 解决方案：
  联网