Docker Daemon

The Docker daemon (command is dockerd) listens for Docker API requests, and manages Docker objects such as images, containers, networks, and volumes. A daemon can also communicate with other daemons across a swarm of computer nodes in order to manage Docker services.

The Docker daemon persists all data in a single directory. This tracks everything related to Docker, including containers, images, volumes, service definition, and secrets. By default this directory is: /var/lib/docker on Linux.

It is a persistent background process that constantly listens for Docker requests, and then processes them. Typically, there is one Docker Daemon running per hardware node. Another way to think about the daemon, is that it is the server that connects you to Docker tools.