国内服务器使用docker拉取镜像出现下载超时问题，直觉问题是网络不通，ping相关的域名或IP发现是无法ping通的，鉴于此本文提供两种方法：
1）添加公开的docker加速代理(下文的代理一段时间后可能失效)：
a）vim /etc/docker/daemon.json
{
"registry-mirrors":
"https://docker.mirrors.sjtug.sjtu.edu.cn", "https://docker.m.daocloud.io", "https://noohub.ru", "https://huecker.io", "https://dockerhub.timeweb.cloud", "https://registry.cn-hangzhou.aliyuncs.com"
}
b）systemctl daemon-reload
c）systemctl restart docker
2）在可连接国外网络的vps或服务器上下载镜像，并迁移：
a) docker pull vulfocus/vulfocus:latest
b)docker save -o /home/test/vulfocus.tar vulfocus/vulfocus:latest
c)拷贝vulfocus.tar至目标服务器/home/test/vulfocus.tar
d)docker load -i /home/test/vulfocus.tar
参考连接：
1、Docker拉取镜像失败，download failed after attempts 6 IO Timeout，Docker拉取镜像失败，download failed after attempts 6 IO Timeout - 南瓜慢说官网
2、Docker Hub 镜像加速器，https://gist.github.com/y0ngb1n/7e8f16af3242c7815e7ca2f0833d3ea6