I installed Docker in my machine where I have Ubuntu OS. After than I installed docker, when I run
sudo docker run hello-world
All it\'s ok
If you want to run docker as non-root user then you need to add it to the docker group.
$ sudo groupadd docker
$ sudo usermod -aG docker $USER
$ newgrp docker
$ docker run hello-world
Reboot if still got error
$ reboot
Taken from the docker official documentation: manage-docker-as-a-non-root-user