错误信息

已加载插件：fastestmirror
Determining fastest mirrors
* base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
base | 3.6 kB ::
extras | 2.9 kB ::
file:///mnt/repodata/repomd.xml: [Errno 14] curl#37 - "Couldn't open file /mnt/repodata/repomd.xml"
正在尝试其它镜像。

One of the configured repositories failed (this is local repo),
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:

 . Contact the upstream for the repository and get them to fix the problem.

 . 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).

 . Run the command with the repository temporarily disabled  
        yum --disablerepo=local ...

 . 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 local  
    or  
        subscription-manager repos --disable=local

 . 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=local.skip\_if\_unavailable=true

failure: repodata/repomd.xml from local: [Errno ] No more mirrors to try.
file:///mnt/repodata/repomd.xml: [Errno 14] curl#37 - "Couldn't open file /mnt/repodata/repomd.xml"
[root@xiaoming ~]# cd /etc/yum.repos.d/

解决办法：

直接删除centos7x64下/etc/yum,repo.d/目录下的所有repo文件，重新导入备份好的CentOS-Bash.repo或者从正常运行的另一台同配置的机器上拷贝CentOS-Bash.repo内容到/etc/yum,repo.d/目录下，然后重新执行yum安装、更新命令，正常可用