Architecture #

• The Docker client talks to the Docker daemon, by using a REST API, over UNIX socket or a network interface

Docker client #

The Docker client (aka.docker) is primary way that many Docker users interact with Docker.

• The docker command uses the Docker API, the Docker client can carry theme out to talk to Docker daemon.
• The Docker client can communicate with more than one daemon.

Docker Compose #

Docker Compose is Another Docker client, that lets you work with applications consisting of a set of containers.

Docker daemon #

• The Docker daemon (aka.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 to manage Docker services.

Docker Registry #

A Docker registry stores Docker images.

• Docker Hub, public registry, can reachable for everyone, by default
• your own private registry, you can configured yourself

Docker Image #

An image is a read-only template with instructions for creating a Docker container. Often, an image is based on another image, with some additional customization.

To build your own image, you create a Dockerfile with a simple syntax for defining the steps needed to create the image and run it.

What's advantage?

• Each instruction in a Dockerfile creates a layer in the image.
• When you change the Dockerfile and rebuild the image, only those layers which have changed are rebuilt. This is part of what makes images so lightweight, small, and fast, when compared to other virtualization technologies.

Docker Container #

A container is also a sandboxed process on your machine that is isolated from all other processes on the host machine.

That isolation leverages kernel namespaces and cgroups, features that have been in Linux for a long time. To summarize, a container:

• is a runnable instance of an image. You can create, start, stop, move, or delete a container using the DockerAPI or CLI.
• can be run on local machines, virtual machines or deployed to the cloud.
• is portable (can be run on any OS).
• is isolated from other containers and runs its own software, binaries, and configurations.

The underlying technology #

• Docker is written in the Go and takes advantage of several features of the Linux kernel to deliver its functionality.
• Docker uses a technology called namespaces to provide the isolated workspace called the container.
• When you run a container, Docker creates a set of namespaces for that container. These namespaces provide a layer of isolation. Each aspect of a container runs in a separate namespace and its access is limited to that namespace.