更换yum源

1. 进入yum源文件目录

   命令：cd /etc/yum.repos.d/

2.  

   先备份一下以免出错后无法补救

   命令：mv ./CentOS-Base.repo ./CentOS-Base.repo.backup

   这段命令的意思是将CentOS-Base.repo 文件重命名为CentOS-Base.repo.backup

3.  

   然后准备下载CentOS-Base.repo文件

   命令：curl -O https://mirrors.aliyun.com/repo/Centos-6.repo

   这将会把url连接的文件下载到当前的目录

4.  

   重新加载

   命令：yum clean all

   命令：yum makecache

5.  

   如果还是无法使用请使用

   命令：cat /etc/yum.repos.d/CentOS-Base.repo

   来检查是否与第6步的代码相同，如果不相同则修改代码与下面相同

6.  

   # CentOS-Base.repo

   #

   # The mirror system uses the connecting IP address of the client and the

   # update status of each mirror to pick mirrors that are updated to and

   # geographically close to the client.  You should use this for CentOS updates

   # unless you are manually picking other mirrors.

   #

   # If the mirrorlist= does not work for you, as a fall back you can try the 

   # remarked out baseurl= line instead.

   #

   #

   [base]

   name=CentOS-6.10 - Base - mirrors.aliyun.com

   failovermethod=priority

   baseurl=http://mirrors.aliyun.com/centos-vault/6.10/os/$basearch/

   gpgcheck=1

   gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

   #released updates 

   [updates]

   name=CentOS-6.10 - Updates - mirrors.aliyun.com

   failovermethod=priority

   baseurl=http://mirrors.aliyun.com/centos-vault/6.10/updates/$basearch/

   gpgcheck=1

   gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

   #additional packages that may be useful

   [extras]

   name=CentOS-6.10 - Extras - mirrors.aliyun.com

   failovermethod=priority

   baseurl=http://mirrors.aliyun.com/centos-vault/6.10/extras/$basearch/

   gpgcheck=1

   gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

   #additional packages that extend functionality of existing packages

   [centosplus]

   name=CentOS-6.10 - Plus - mirrors.aliyun.com

   failovermethod=priority

   baseurl=http://mirrors.aliyun.com/centos-vault/6.10/centosplus/$basearch/

   gpgcheck=1

   enabled=0

   gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

   #contrib - packages by Centos Users

   [contrib]

   name=CentOS-6.10 - Contrib - mirrors.aliyun.com

   failovermethod=priority

   baseurl=http://mirrors.aliyun.com/centos-vault/6.10/contrib/$basearch/

   gpgcheck=1

   enabled=0

   gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6