阿里云 'AppStream': Cannot download repomd.xml: Cannot download repodata/repomd.xml
阿里云 'everything': Cannot download repomd.xml: Cannot download repodata/repomd.xml
阿里云yum安装软件报错
故障原因：由于cenos8停服，后继版本为8-steam.
查看阿里云上的https://mirrors.aliyun.com/centos/8 发现文件已经不完整，我直接把8更换为了8-stream
这个是阿里云官方解决办法：https://help.aliyun.com/document_detail/405635.html
下面是我以前的处理方法：
删除或移走/etc/yum.repos.d内的CentOS-AppStream.repo，CentOS-epel.repo
编辑/etc/yum.repos.d/CentOS-Base.repo 替换为以下内容，
# 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-8-stream - Base - mirrors.aliyun.com failovermethod=priority baseurl=https://mirrors.aliyun.com/centos/8-stream/BaseOS/$basearch/os/ gpgcheck=1 gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official #additional packages that may be useful [extras] name=CentOS-8-stream - Extras - mirrors.aliyun.com failovermethod=priority baseurl=https://mirrors.aliyun.com/centos/8-stream/extras/$basearch/os/ gpgcheck=1 gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official #additional packages that extend functionality of existing packages [centosplus] name=CentOS-8-stream - Plus - mirrors.aliyun.com failovermethod=priority baseurl=https://mirrors.aliyun.com/centos/8-stream/centosplus/$basearch/os/ gpgcheck=1 enabled=0 gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official [PowerTools] name=CentOS-8-stream - PowerTools - mirrors.aliyun.com failovermethod=priority baseurl=https://mirrors.aliyun.com/centos/8-stream/PowerTools/$basearch/os/ gpgcheck=1 enabled=0 gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official [AppStream] name=CentOS-8-stream - AppStream - mirrors.aliyun.com failovermethod=priority baseurl=https://mirrors.aliyun.com/centos/8-stream/AppStream/$basearch/os/ gpgcheck=1 gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-Official
然后执行
yum clean all
yum makecache
会发现问题已经解决，centos8 替换成centos8-steam后，对系统的影响还不知道，暂时问题解决，可以顺利yum安装mysql等软件