Linux 通过 VM 的 Centos 镜像列表中没有 URL

我试图通过VirtualBox(6.1.30)(Vagrant)运行Centos 8服务器，昨天对我来说效果很好，但今天我try 运行sudo yum update，因为某些原因，我一直遇到这个错误:

[vagrant@192.168.38.4] ~  >> sudo yum update
CentOS Linux 8 - AppStream                       71  B/s |  38  B     00:00
Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist

我已经try 更改/etc/resolve.conf上的名称空间，删除dnf文件夹和所有内容.在其他计算机上，这一切正常，所以我认为问题出在我的主机上.还试图重置网络设置(我在win 10主机上)，但也没有成功.这不是DNS问题，它工作正常.

更新:我重新安装了windows，在我的虚拟机上仍然有相同的错误

dnf.日志(log):

2022-01-31T15:28:03+0000 INFO --- logging initialized ---
2022-01-31T15:28:03+0000 DDEBUG timer: config: 2 ms
2022-01-31T15:28:03+0000 DEBUG Loaded plugins: builddep, changelog, config-manager, copr, debug, debuginfo-install, download, generate_completion_cache, groups-manager, needs-restarting, playground, repoclosure, repodiff, repograph, repomanage, reposync
2022-01-31T15:28:03+0000 DEBUG YUM version: 4.4.2
2022-01-31T15:28:03+0000 DDEBUG Command: yum update
2022-01-31T15:28:03+0000 DDEBUG Installroot: /
2022-01-31T15:28:03+0000 DDEBUG Releasever: 8
2022-01-31T15:28:03+0000 DEBUG cachedir: /var/cache/dnf
2022-01-31T15:28:03+0000 DDEBUG Base command: update
2022-01-31T15:28:03+0000 DDEBUG Extra commands: ['update']
2022-01-31T15:28:03+0000 DEBUG User-Agent: constructed: 'libdnf (CentOS Linux 8; generic; Linux.x86_64)'
2022-01-31T15:28:05+0000 DDEBUG Cleaning up.
2022-01-31T15:28:05+0000 SUBDEBUG
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 574, in load
    ret = self._repo.load()
  File "/usr/lib64/python3.6/site-packages/libdnf/repo.py", line 397, in load
    return _repo.Repo_load(self)
libdnf._error.Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 67, in main
    return _main(base, args, cli_class, option_parser_class)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 106, in _main
    return cli_run(cli, base)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 122, in cli_run
    cli.run()
  File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 1050, in run
    self._process_demands()
  File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 740, in _process_demands
    load_available_repos=self.demands.available_repos)
  File "/usr/lib/python3.6/site-packages/dnf/base.py", line 394, in fill_sack
    self._add_repo_to_sack(r)
  File "/usr/lib/python3.6/site-packages/dnf/base.py", line 137, in _add_repo_to_sack
    repo.load()
  File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 581, in load
    raise dnf.exceptions.RepoError(str(e))
dnf.exceptions.RepoError: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist
2022-01-31T15:28:05+0000 CRITICAL Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist