今天搭建k8s集群时，发现一系列k8s.gcr.io的镜像无法pull：

-<%>- docker pull k8s.gcr.io/kube-proxy
Using default tag: latest
Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

原来是万恶的某沃尔，需要为docker设置代理，并重启docker daemon：

sudo mkdir -p /etc/systemd/system/docker.service.d 
sudo touch /etc/systemd/system/docker.service.d/proxy.conf
sudo chmod 777 /etc/systemd/system/docker.service.d/proxy.conf
sudo echo '
[Service]
Environment="HTTP_PROXY=http://proxy.xxx.com:8888/" 
Environment="HTTPS_PROXY=http://proxy.xxx.com:8888/"
' >> /etc/systemd/system/docker.service.d/proxy.conf
sudo systemctl daemon-reload
sudo systemctl restart docker

通过systemctl查看配置结果：

sudo systemctl show --property=Environment docker

之后再次拉取镜像，成功。