Repository AppStream is listed more than once in the configuration

root@centos8 ~ yum install gcc
Repository AppStream is listed more than once in the configuration
Repository extras is listed more than once in the configuration
Repository PowerTools is listed more than once in the configuration
Repository centosplus is listed more than once in the configuration
Repository AppStream is listed more than once in the configuration
Repository PowerTools is listed more than once in the configuration
Repository base is listed more than once in the configuration
Repository centosplus is listed more than once in the configuration
Repository extras is listed more than once in the configuration

解决方案：

备份文件

cd /etc/yum.repos.d && mkdir bak && mv *.repo ./bak

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

生成缓存

yum clean all
yum makecache