Understanding Docker Architecture: Images, Containers, and Core Components

Docker uses container technology to help developers build, package, publish, and run applications.

Compared with traditional virtualization, Docker containers are lighter, start faster, and provide easier environment isolation and migration.

Docker Architecture

Docker architecture consists of three core components: images, registries, and containers.

Docker Images

A Docker image is a read‑only template that includes all files, libraries, code, and runtime needed to run a container. It can be thought of as a blueprint for creating containers.

Images are built with docker build -t myapp:1.0 . and listed with docker images. They use layered storage, where each read‑only layer makes building and distributing images efficient.

Docker Registry

A Docker registry stores and distributes Docker images. There are public registries such as Docker Hub and private registries that organizations can host for internal use.

Docker Containers

A Docker container is a lightweight, portable, self‑contained runtime environment created from an image. It packages the application code, runtime, libraries, and configuration files.

Containers run as isolated processes using Linux namespaces and cgroups, which provide resource isolation and limits, making each container appear as an independent OS environment.

Namespaces

Namespaces partition system resources so that each container sees its own isolated view of resources, invisible to other containers or the host.

Cgroups

Cgroups (control groups) allow the kernel to allocate, limit, monitor, and reclaim resources for a group of processes. The cgroup hierarchy can be inspected under /sys/fs/cgroup/....

These components work together to form Docker’s basic workflow, enabling fast, isolated, and manageable application deployment.