wget -qO- https://get.docker.com/ | sh # download a script and execute with sh
sudo usermod -aG docker <your username> # this is to add your username to docker group.
newgrp docker # 更新用户组
中途可能报错
The repository 'http://ppa.launchpad.net/fcitx-team/nightly/ubuntu xenial Release' does not have a Release file.
在ubuntu->system setting->Software & Update ->Other Softwares取消http://ppa.launchpad.net/fcitx-team/nightly/ubuntu xenial Release的选项，跳出更新按钮，更新之(可能和sudo apt-get update作用相同？)。
再次安装即可。
还有其他方法是删除/etc/apt/sources.list.d/fcitx-team-ubuntu-nightly-xenial.list 未尝试。