我在全新安装的 Centos 8 上，并首次尝试使用 yum（在这台机器上）。每次尝试安装或更新任何内容时，我都会收到以下信息：
yum update
CentOS-8 - AppStream 0.0 B/s | 0 B 00:00
Failed to download metadata for repo 'AppStream'
Error: Failed to download metadata for repo 'AppStream'
端口 80 是打开的，尽管 nmap 报告它已关闭，大概是因为我还没有安装 apache。为了确保万无一失，我已将端口 80 添加到了防火墙，这已得到确认：
firewall-cmd --list-ports
25/tcp 80/tcp
我尝试了各种建议，例如 yum clean 和清除 yum 缓存，但没有任何帮助。
dnf.log 中的内容如下：
2020-03-30T19:33:01Z INFO --- logging initialized ---
2020-03-30T19:33:01Z DDEBUG timer: config: 4 ms
2020-03-30T19:33:01Z DEBUG Loaded plugins: builddep, changelog, config-manager, copr, debug, debuginfo-install, download, generate_completion_cache, needs-restarting, playground, repoclosure, repodiff, repograph, repomanage, reposync
2020-03-30T19:33:01Z DEBUG DNF version: 4.2.7
2020-03-30T19:33:01Z DDEBUG Command: yum install httpd
2020-03-30T19:33:01Z DDEBUG Installroot: /
2020-03-30T19:33:01Z DDEBUG Releasever: 8
2020-03-30T19:33:01Z DEBUG cachedir: /var/cache/dnf
2020-03-30T19:33:01Z DDEBUG Base command: install
2020-03-30T19:33:01Z DDEBUG Extra commands: ['install', 'httpd']
2020-03-30T19:33:01Z DEBUG repo: downloading from remote: AppStream
2020-03-30T19:33:02Z DEBUG error: Curl error (6): Couldn't resolve host name for http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock [Could not resolve host: mirrorlist.centos.org] (http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock).
2020-03-30T19:33:02Z DEBUG Cannot download 'http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock': Cannot prepare internal mirrorlist: Curl error (6): Couldn't resolve host name for http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=AppStream&infra=stock [Could not resolve host: mirrorlist.centos.org].
2020-03-30T19:33:02Z ERROR Failed to download metadata for repo 'AppStream'
2020-03-30T19:33:02Z DDEBUG Cleaning up.
2020-03-30T19:33:02Z SUBDEBUG
Traceback (most recent call last):
File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 552, in load
ret = self._repo.load()
File "/usr/lib64/python3.6/site-packages/libdnf/repo.py", line 394, in load
return _repo.Repo_load(self)
RuntimeError: Failed to download metadata for repo 'AppStream'
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 65, in main
return _main(base, args, cli_class, option_parser_class)
File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 98, in _main
return cli_run(cli, base)
File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 114, in cli_run
cli.run()
File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 1134, in run
self._process_demands()
File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 832, in _process_demands
load_available_repos=self.demands.available_repos)
File "/usr/lib/python3.6/site-packages/dnf/base.py", line 406, in fill_sack
self._add_repo_to_sack(r)
File "/usr/lib/python3.6/site-packages/dnf/base.py", line 136, in _add_repo_to_sack
repo.load()
File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 558, in load
raise dnf.exceptions.RepoError(str(e))
dnf.exceptions.RepoError: Failed to download metadata for repo 'AppStream'
2020-03-30T19:33:02Z CRITICAL Error: Failed to download metadata for repo 'AppStream'
答案1
显然这不是问题所在，但如果你有固定您将自己升级到 CentOS 8.1.1911，您将得到同样的错误，直到您将 /etc/yum.repos.d/ 存储库重新指向http://vault.centos.org代替http://mirror.centos.org
答案2
您需要连接到互联网才能下载软件包。
检查您是否有 IP 地址（使用ip a）、是否有默认路由（使用ip r）以及是否定义了名称服务器，以便可以解析名称（使用cat /etc/resolv.conf）。
答案3
以真主的名义。我认为这个问题的原因是 CentOS 版本的生命终结。
CentOS Linux 7 EOL: 2024-06-30
CentOS Linux 8 EOL: 2021-12-31
CentOS Stream 8 EOL: 2024-05-31
CentOS Stream 9 EOL: estimated 2027, dependent on RHEL9 end of “Full Support Phase”
所以我从 CentOS Linux 8 迁移到 CentOS Stream。
注意你的服务器必须是最新的。在操作环境中，它与风险相关。
#dnf 安装 centos-release-stream
#dnf 交换 centos-{linux,stream}-repos
#dnf 发行版同步
说明位于以下网址： https://www.tecmint.com/migrate-centos-8-to-centos-stream/
