One of the configured repositories failed (Unknown),  
 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 find a valid baseurl for repo: base/7/x86_64 
 

一、不能使用yum映象

      vi /etc/resolv.conf，新增下面一行就可以了

       nameserver 114.114.114.114（這是國內的dns伺服器系統，還是比較好用的。谷歌的可以使用8.8.8.8）  

二、阿里映象配置

1、開啟centos的yum資料夾

輸入命令cd  /etc/yum.repos.d/

2、用wget下載repo檔案

輸入命令wget  http://mirrors.aliyun.com/repo/Centos-7.repo

如果wget命令不生效，說明還沒有安裝wget工具，輸入yum -y install wget 回車進行安裝。

當前目錄是/etc/yum.repos.d/，剛剛下載的Centos-7.repo也在這個目錄上

3、備份系統原來的repo檔案

mv  CentOs-Base.repo CentOs-Base.repo.bak

即是重新命名 CentOs-Base.repo -> CentOs-Base.repo.bak

4、替換系統原理的repo檔案

mv Centos-7.repo CentOs-Base.repo

即是重新命名 Centos-7.repo -> CentOs-Base.repo

5、執行yum源更新命令

yum clean all

yum makecache

yum update

依次執行上述三條命令即配置完畢。

--------------------- 作者：ltx06 來源：CSDN 原文：https://blog.csdn.net/ltx06/article/details/78030056?utm_source=copy 版權宣告：本文為博主原創文章，轉載請附上博文連結！