使用华为云Centos7.x服务Yum安装软件的时候提示错误：

Error: Failed to download metadata for repo ‘epel’: Cannot download repomd.xml

需要修改Centos的yum下载源配置，逐条执行以下命令对源进行替换即可：

cd /etc/yum.repos.d

mkdir yumbak

mv *.repo yumbak

wget -O /etc/yum.repos.d/CentOS-Base.repo https://repo.huaweicloud.com/repository/conf/CentOS-8-reg.repo

sed -i "s/\$releasever/8-stream/g" /etc/yum.repos.d/CentOS-Base.repo

yum clean all

yum makecache

yum list