Failed to download metadata for repo ‘AppStream‘: Cannot download repomd.xml: Cannot download repoda

CentOS在使用yum命令的时候报错：Failed to download metadata for repo ‘AppStream’: Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried 原因：2022年1月1日起CentOS官方将不再对CentOS 8提供服务支持,虽然系统可以正常使用,但CentOS 8的yum源已经移除无法使用了,使用yum安装会报错 解决方法：

按顺序执行一下命令即可解决：
1.执行如下命令先将之前的yum文件备份：

rename '.repo' '.repo.bak' /etc/yum.repos.d/*.repo

2.运行以下命令下载最新的repo文件：

wget https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo -O /etc/yum.repos.d/Centos-vault-8.5.2111.repo

wget https://mirrors.aliyun.com/repo/epel-archive-8.repo -O /etc/yum.repos.d/epel-archive-8.repo

3.运行以下命令替换repo文件中的链接：

sed -i 's/mirrors.cloud.aliyuncs.com/url_tmp/g'  /etc/yum.repos.d/Centos-vault-8.5.2111.repo &&  sed -i 's/mirrors.aliyun.com/mirrors.cloud.aliyuncs.com/g' /etc/yum.repos.d/Centos-vault-8.5.2111.repo && sed -i 's/url_tmp/mirrors.aliyun.com/g' /etc/yum.repos.d/Centos-vault-8.5.2111.repo

sed -i 's/mirrors.aliyun.com/mirrors.cloud.aliyuncs.com/g' /etc/yum.repos.d/epel-archive-8.repo

4.运行以下命令重新创建缓存,若没报错,则正常了

yum clean all && yum makecache