使用yum 安装bind 这样报错安装失败是怎么回事？

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Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"

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. 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

Cannot find a valid baseurl for repo: base/7/x86_64

• 这篇博客: 使用yum命令安装报错中的 常见错误1：curl#6 - “Could not resolve host: mirrorlist.centos.org; 未知的错误” 部分也许能够解决你的问题, 你可以仔细阅读以下内容或跳转源博客中阅读:
  

• Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was
  14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"
  
   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. 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
  
  Cannot find a valid baseurl for repo: base/7/x86_64