项目场景：

新安装的CentOS 8 系统，官方源虽然可以使用但是下载速度较为感人，而且有的软件库中也不存在，当换成国内的源时出现了错误。

问题描述：

按照网易的操作指南更换网易的源时发生了错误。因为它只有：
CentOS7
CentOS6
CentOS5
没有CentOS8的将CentOS7的放上面也不行。报如下错：

[root@localhost yum.repos.d]# yum makecache 
CentOS-8 - Base - 163.com                                                                         449  B/s | 162  B     00:00    
Errors during downloading metadata for repository 'base':
  - Status code: 404 for http://mirrors.163.com/centos/8/os/x86_64/repodata/repomd.xml (IP: 111.19.255.245)
错误：为 repo 'base' 下载元数据失败 : Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

原因分析：

管他什么原因，直接ctrl+c、ctrl+v就是干。不报错就ok走人。

解决方案：

将原有的/etc/yum.repos.d/CentOS-Base.repo备份，然后在此目录新建CentOS-Base.repo。
将上述文件用vim打开，将下述述代码片复制上去。

### cat CentOS-Base.repo ###
[base]
name=CentOS-8 - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8/BaseOS/x86_64/os/
        http://mirrors.aliyuncs.com/centos/8/BaseOS/x86_64/os/
        http://mirrors.cloud.aliyuncs.com/centos/8/BaseOS/x86_64/os/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official


### cat CentOS-AppStream.repo ###
[AppStream]
name=CentOS-8 - AppStream - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8/AppStream/x86_64/os/
        http://mirrors.aliyuncs.com/centos/8/AppStream/x86_64/os/
        http://mirrors.cloud.aliyuncs.com/centos/8/AppStream/x86_64/os/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official


### cat CentOS-Extras.repo ###
[extras]
name=CentOS-8 - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8/extras/x86_64/os/
        http://mirrors.aliyuncs.com/centos/8/extras/x86_64/os/
        http://mirrors.cloud.aliyuncs.com/centos/8/extras/x86_64/os/
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official


### cat CentOS-Epel.repo ###
[epel]
name=CentOS-$releasever - Epel
baseurl=http://mirrors.aliyun.com/epel/8/Everything/$basearch
enabled=1
gpgcheck=0


### cat CentOS-PowerTools.repo ###
[PowerTools]
name=CentOS-8 - PowerTools - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8/PowerTools/x86_64/os/
        http://mirrors.aliyuncs.com/centos/8/PowerTools/x86_64/os/
        http://mirrors.cloud.aliyuncs.com/centos/8/PowerTools/x86_64/os/
gpgcheck=1
enabled=0
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official


### cat CentOS-centosplus.repo ###
[centosplus]
name=CentOS-8 - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/8/centosplus/x86_64/os/
        http://mirrors.aliyuncs.com/centos/8/centosplus/x86_64/os/
        http://mirrors.cloud.aliyuncs.com/centos/8/centosplus/x86_64/os/
gpgcheck=1
enabled=0
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official

运行以下命令生成缓存

yum clean all
yum makecache