docker安裝后不能正常啟動，報錯如下
$ sudo docker image ls
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
systemctl status docker.service
● docker.service - LSB: Create lightweight, portable, self-sufficient containers.
Loaded: loaded (/etc/init.d/docker; generated)
Active: failed (Result: exit-code) since Tue 2018-06-05 15:18:48 CST; 6min ago
Docs: man:systemd-sysv-generator(8)
Process: 28643 ExecStart=/etc/init.d/docker start (code=exited, status=1/FAILURE)
Main PID: 9695 (code=exited, status=0/SUCCESS)
6月 05 15:18:48 MaLiJun-Ubuntu systemd[1]: Starting LSB: Create lightweight, portable, self-sufficient containers....
6月 05 15:18:48 MaLiJun-Ubuntu docker[28643]: * /usr/bin/dockerd not present or not executable
6月 05 15:18:48 MaLiJun-Ubuntu systemd[1]: docker.service: Control process exited, code=exited status=1
6月 05 15:18:48 MaLiJun-Ubuntu systemd[1]: docker.service: Failed with result 'exit-code'.
6月 05 15:18:48 MaLiJun-Ubuntu systemd[1]: Failed to start LSB: Create lightweight, portable, self-sufficient containers..
網上沒有找到合適的當解決方案，耽誤了很多時間，於是重新安裝
從ubuntu 倉庫直接下載最方便(不是安裝的最新版)：
$ sudo apt install docker.io $ sudo systemctl start docker $ sudo systemctl enable docker $ docker container ls --all