CentOS 8 yum 报错 No URLs in mirrorlist 解决

CentOS 8 已 EOL，官方 mirror 下线，yum 报错：

Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist

方案一：改用阿里源

cd /etc/yum.repos.d
# 修改 CentOS-Base.repo / CentOS-AppStream.repo / CentOS-Extras.repo
# 注释 mirrorlist，将 baseurl 改为阿里源，例如：
# baseurl=https://mirrors.aliyun.com/centos/8-stream/BaseOS/x86_64/os/
# baseurl=https://mirrors.aliyun.com/centos/8-stream/AppStream/x86_64/os/
# baseurl=https://mirrors.aliyun.com/centos/8-stream/extras/x86_64/os/

方案二：改用 vault 源（一键 sed）

cd /etc/yum.repos.d/
sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*
yum update -y