cannot connect to docker daemon at unix ///var/run/docker.sock code example

Example 1: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.40/containers/json: dial unix /var/run/docker.sock: connect: permission denied

sudo usermod -aG docker ${USER}

Example 2: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock

sudo chmod 666 /var/run/docker.sock

Example 3: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

sudo dockerd

Example 4: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.

sudo su
systemctl start docker
systemctl enable docker
systemctl restart docker