解决centos8 Failed to download metadata for repo 'AppStream'等错误

• 在2022年1月31日，CentOS团队终于从官方镜像中移除CentOS 8的所有包。

• CentOS 8已于2021年12月31日寿终正寝，但软件包仍在官方镜像上保留了一段时间。现在他们被转移到https://vault.centos.org

• 将源切换为清华、腾讯或阿里

1. 清华
   清华镜像使用帮助
2. 阿里
   阿里镜像使用帮助
3. 腾讯

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.cloud.tencent.com/repo/centos8_base.repo

• 清理之前的yum缓存

[root@VM-12-9-centos ~]# yum clean all
Invalid configuration value: failovermethod=priority in /etc/yum.repos.d/CentOS-Epel.repo; Configuration: OptionBinding with id "failovermethod" does not exist
Repository extras is listed more than once in the configuration
Repository fasttrack is listed more than once in the configuration
Repository epel is listed more than once in the configuration
42 files removed

• 建立新的缓存

[root@VM-12-9-centos ~]# sudo yum makecache
Invalid configuration value: failovermethod=priority in /etc/yum.repos.d/CentOS-Epel.repo; Configuration: OptionBinding with id "failovermethod" does not exist
Repository extras is listed more than once in the configuration
Repository fasttrack is listed more than once in the configuration
Repository epel is listed more than once in the configuration
Qcloud centos OS - x86_64                                                                                                                                                                                 6.3 MB/s | 4.5 MB     00:00
already tried without success

• 在上两步之前，还需要删除之前已经失效的仓库