System version:ubuntu-server 16.04
Docker version:Docker version 17.03.0-ce, build 60ccb22

Try to executedocker info, reported the wrong said didn’t start:

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

Then executeservice docker start, report an error:

Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details.

carry outsystemctl status docker.serviceThe view log displays as follows:

● docker.service - Docker Application Container Engine
 Loaded: loaded (/lib/systemd/system/docker.service;   enabled;  vendor preset: enabled)
 Active: failed (Result: exit-code) since Fri 2017-03-31 09:58:52 CST;  1min 31s ago
 Docs:  https://docs.docker.com
 Process: 21336 ExecStart=/usr/bin/dockerd -H fd:// (code=exited, status=1/FAILURE)
 Main PID: 21336 (code=exited, status=1/FAILURE)
 
 Mar 31 09:58:52 ip-101-37-28-246 systemd[1]: Starting Docker Application Container Engine  ...
 Mar 31 09:58:52 ip-101-37-28-246 dockerd[21336]: unable to configure the Docker daemon with file /etc/docker/daemon.json: EOF
 Mar 31 09:58:52 ip-101-37-28-246 systemd[1]: docker.service: Main process exited, code=exited, status=1/FAILURE
 Mar 31 09:58:52 ip-101-37-28-246 systemd[1]: Failed to start Docker Application Container Engine.
 Mar 31 09:58:52 ip-101-37-28-246 systemd[1]: docker.service: Unit entered failed state.
 Mar 31 09:58:52 ip-101-37-28-246 systemd[1]: docker.service: Failed with result 'exit-code'.

I used it about 3 days ago and it was ok. I couldn’t use it after logging in yesterday.