SHELL

Start the Docker daemon

sudo systemctl start docker
sudo service docker start

Is the docker daemon running?

sudo dockerd

docker daemon

dockerd

what is docker daemon

Docker daemon is a persistent background process that manages the containers on
a single host. 
It is a self-sufficient runtime that manages Docker objects 
such as images, containers, network, and storage. 
Docker daemon listens for REST API requests and performs a series of 
container operations accordingly.

GET /events: Get container events from Docker
GET /images/json: List Docker images

By default this directory is: /var/lib/docker on Linux. C:ProgramDatadocker on Windows.