For Ubuntu 16.04.
Pull with docker pull daocloud.io/mysql:5.7 makes it faster a little.
Pull with docker pull registry.docker-cn.com/library/mysql:5.7 makes it faster a little.
Add the foloowing line to /etc/default/docker:
DOCKER_OPTS="--dns 8.8.8.8 --dns 8.8.4.4 --registry-mirror=https://docker.mirrors.ustc.edu.cn"
Restart docker service:
sudo systemctl restart docker