I found it a little annoying having to prefix my docker instance start up commands with sudo all the time, these simple steps eliminate the need for the sudo command.

Simply edit the file /etc/group and add your linux username to the docker group.  My entry looks like this (for the username csw):

docker:x:999:csw

The following command may save you from logging out and back in

newgrp docker

Try running docker ps, if it doesn't work you'll need to logout and back in for the changes to take effect.

All done, you can now run docker run command without the need to sudo to the super user!