You are trying to run a docker container or do the docker tutorial, but you only get an error message like this:
docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: ... dial unix /var/run/docker.sock: connect: permission denied. See 'docker run --help'.
As a temporary solution, you can use sudo to run the failed command as root. However it is recommended to fix the issue by adding the current user to the docker group:
Run this command in your favourite shell and then completely reboot:
sudo usermod -a -G docker $USER sudo reboot