Firstly the user has to try with sudo, as the current users may not have permission to access for communicating with docker daemon like /var/run/docker.sock.
If this not working yet then after installing, simply stop the docker daemon by using the command;
$ sudo service docker stop
And after this run the following command to start the daemon in the background.
$ sudo nohup docker daemon –H tcp://0.0.0.0:2375 –H unix:///var/run/docker.sock.
To make the working environment user friendly, the users have to add your username to the Docker users group. The user can be added to a group by using the following command;
$ sudo usermod –aG docker $USER
These steps are also mentioned at the official documentation of docket Post-Installation steps for Linux.
For Ubuntu 16.04 Users:
The users who are using Ubuntu 16.04 can follow these steps;
Inside the file /lib/systemd/system/docker.service change: ExecStart=/usr/bin/dockerd fd:// with ExecStart=/usr/bin/dockerd –H tcp://0.0.0.0:2375
Inside the file /etc/init.d/docker change:
DOCKER_OPTS=”H ***tcp:// 0.0.0.0:2375”
After this restart your machine and start playing with docker. This will help to solve your errors.