尝试从任何 repo 更新任何包时，很难追踪导致以下错误的原因。我通过将所有其他存储库设置为禁用来测试多个存储库。我已经清理了所有缓存并删除了所有 dnf yum 缓存文件。
# dnf -v update
Loaded plugins: builddep, changelog, config-manager, copr, debug, debuginfo-install, download, generate_completion_cache, needs-restarting, playground, repoclosure, repodiff, repograph, repomanage, reposync
DNF version: 4.2.7
cachedir: /var/cache/dnf
repo: downloading from remote: AppStream
error: Curl error (28): Timeout was reached for http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock [Resolving timed out after 30000 milliseconds] (http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock).
CentOS-8 - AppStream 0.0 B/s | 0 B 00:30
Cannot download 'http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock': Cannot prepare internal mirrorlist: Curl error (28): Timeout was reached for http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock [Resolving timed out after 30000 milliseconds].
Failed to download metadata for repo 'AppStream'
Error: Failed to download metadata for repo 'AppStream'
每次我尝试更新 dnf 时，服务器上的平均负载都会飙升，高达 40 倍
curl 可以访问镜像站点。
curl 'http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock'
http://ftp.tc.edu.tw/Linux/CentOS/8.2.2004/AppStream/x86_64/os/
http://mirror.horizon.vn/centos/8.2.2004/AppStream/x86_64/os/
http://ftp.jaist.ac.jp/pub/Linux/CentOS/8.2.2004/AppStream/x86_64/os/
http://centosg9.centos.org/centos/8.2.2004/AppStream/x86_64/os/
http://packet01.centos.org/centos/8.2.2004/AppStream/x86_64/os/
http://mirror.s8.centos.org/centos/8.2.2004/AppStream/x86_64/os/
http://centoso7.centos.org/centos/8.2.2004/AppStream/x86_64/os/
http://centosh9.centos.org/centos/8.2.2004/AppStream/x86_64/os/
http://centosc8.centos.org/centos/8.2.2004/AppStream/x86_64/os/
http://centosg7.centos.org/centos/8.2.2004/AppStream/x86_64/os/
我也试过在.repo中使用baserurl，同样的错误
我还用 curl 返回的 URL 之一替换了 baseurl，同样的错误
我尝试了很多建议，例如yum/dnf error: Failed to download metadata for repo and similar，没有一个对我有用。一些文章指出了 $releaseserver 等环境变量中的错误。我也尝试用实际值替换。同样的错误。
由于 curl 结果，Internet 连接显然可以。没有使用代理。DNS 正常
cat /etc/redhat-release
CentOS Linux release 8.1.1911 (Core)
uname -a
Linux xxxx 4.18.0-147.5.1.el8_1.x86_64 #1 SMP Wed Feb 5 02:00:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
任何建议将不胜感激。