docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?. See 'docker run --help'.

This error message indicates that the Docker daemon is not running on your system, or that the Docker client is unable to connect to it. To resolve this issue, you can try the following steps:

1. Start the Docker daemon: You can do this by running the command `sudo systemctl start docker` on Linux or `docker run hello-world` on Windows or macOS. This will start the Docker daemon and allow the Docker client to connect to it.

2. Check if the Docker daemon is running: You can run the command `sudo systemctl status docker` on Linux or `docker ps` on Windows or macOS to check if the Docker daemon is running. If it is not running, you will need to start it as described in step 1.

3. Check Docker socket permissions: Ensure that the Docker socket file (/var/run/docker.sock) has the correct permissions. You can run the command `ls -l /var/run/docker.sock` to check the permissions. The owner should be root and the group should be docker. If the permissions are incorrect, you can change them by running the command `sudo chown root:docker /var/run/docker.sock`.

4. Check if Docker is installed: If you have recently installed Docker, make sure that it is installed correctly. You can run the command `docker version` to check if Docker is installed and running correctly.

5. Check if Docker is running in a container: If you are running Docker in a container, make sure that the container is running and that the Docker daemon is started within the container.

If none of these steps resolve your issue, you may need to refer to the Docker documentation or seek assistance from the Docker community.