centos8清华源-for repo ‘appstream‘ 和for repo ‘baseos‘: Cannot download repomd.xml

【错误1】：

[root@ngx yum.repos.d]# yum makecache

CentOS Linux 8 - AppStream                                                                                                                                                     146  B/s | 153  B     00:01

Errors during downloading metadata for repository 'appstream':

  - Status code: 404 for https://mirrors.tuna.tsinghua.edu.cn/centos/8/AppStream/x86_64/os/repodata/repomd.xml (IP: 101.6.15.130)

Error: Failed to download metadata for repo 'appstream': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

[root@ngx yum.repos.d]#

【处理】：

修改 /etc/yum.repos.d/Cent