Using systemd to control the Docker daemon - Docker, Inc.
The nice thing about the command above is that it shows a unified view of all options and takes into consideration any overrides that may have been applied.
Tue Oct 10 11:21:10 2017
To change the value of an option, ExecStart in this case, do the following:
[ec2-user@ip-10-0-46-113 ~]$ sudo systemctl edit docker
This will create the necessary directory structure under /etc/systemd/system/docker.service.dand open an editor (using the default editor configured for the user) to the override file. Add the section below into the editor:
ExecStart=/usr/bin/docker daemon -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock
It was necessary to clear out ExecStart using ExecStart= before setting it to the override value. This is only required for some options and most options in the configuration file would not need to be cleared like this