Solution to cannot connect to the docker daemon Error

There are two reasons you get the "cannot connect to the docker daemon" error message when try to run docker command.

One reason is docker service is not running. So first of all make sure that docker service is running.

systemctl is-active docker

If service is not active, then start and enable the docker service.

systemctl start docker
systemctl enable docker

Another reason could be you are trying to run the docker command as non root user.

Non root users can run the docker command if you add the user to the docker group.

Create the Docker group if it is not there already:

sudo groupadd docker

Restart the Docker Service:

sudo systemctl restart docker

Add the user to the docker group:

sudo usermod -a -G docker username

Now re login to the user account and try to run the docker command without sudo in front.

This time you should not get the error message "Cannot connect to the Docker daemon. Is the docker daemon running on this host?".