完美解决 CentOS解决yum命令出现doesn't have enough cached的问题

问题

配置CentOS的时候遇到以下问题：

[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
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网上搜索了其他人的解决方法，都是复制粘贴的博客，基本都是一样，但是我尝试过之后无效，这个问题还是存在。 如果你也遇到了这个问题，使用了其他方法解决不了，可以尝试一下我的解决方法。

解决方法

我的解决方法是修改默认yum源为阿里云yum源，亲测有效。

步骤如下：

1. 备份原有yum源：

    mv /etc/yum.repos.d /etc/yum.repos.d.bak
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2. 创建yum源目录

   mkdir /etc/yum.repos.d
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3. 下载阿里云yum源配置

   wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
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4. 重建缓存

   yum clean all
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  yum makecache
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