centos8 yum失效后解决方法

CentOS Stream 8 - BaseOS 25 B/s | 150 B 00:05
Errors during downloading metadata for repository 'baseos':

Status code: 404 for https://mirrors.ustc.edu.cn/centos/8-stream/BaseOS/x86_64/os/repodata/repomd.xml (IP: 218.104.71.170)
Error: Failed to download metadata for repo 'baseos': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

# 在命令行中执行
sed -i 's|centos/\$stream|centos-vault/8.5.2111|g' /etc/yum.repos.d/base.repo
yum clean all
yum makecache