What is a container?
A container is a lightweight box that packs a program with everything it needs so it runs the same on any computer.
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A container bundles an application together with its libraries, settings and runtime into one isolated package that shares the host’s operating system kernel. Picture a shipping container: the crane and ship do not care what is inside, they only need a standard box. In software the standard box means your app runs identically on a laptop, a test server and a cloud machine.
Containers are what you start with docker run. Developers use them to avoid the classic excuse that it works on my machine, operations teams use them to deploy many small services on a single host, and platforms like Kubernetes exist only to run containers at scale. Unlike a virtual machine, a container starts in a second and uses little memory.
docker run --rm -it alpine shSee also: What is a virtual machine? and What is Kubernetes?
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See also
- 0055 Docker basics: images, containers and the commands you need An image is a read-only package of an app and its dependencies, and a container is a running instance of it. Learn… Beginner · Explains an idea · Linux, macOS, Windows Article Docker basics 15 Oct 2026
- 0056 Docker Compose: run a small web app with a database Docker Compose describes several containers, their ports, volumes and environment in one compose.yaml file, then starts them all with docker compose up. Intermediate · Step by step · Linux, macOS, Windows Article Docker basics · Docker Compose 15 Oct 2026
- 0250 Containerize a Node.js app and run it with PostgreSQL using Docker Compose Package a small Node.js web app in a multi-stage Docker image, then run it next to PostgreSQL with Docker Compose, named volumes,… Intermediate · Guided project · Linux, macOS, Windows Article Docker basics · Docker Compose · PostgreSQL 15 Oct 2026
- 0327 Docker images, containers and volumes explained An image is a read-only template, a container is a running copy of it with a thin writable layer, and a volume… Beginner · Explains an idea · Linux, macOS, Windows Article Docker basics 15 Oct 2026
- 0328 Install Docker Engine on Ubuntu and Debian Set up Docker's official apt repository, install Docker Engine with the Compose and Buildx plugins, run hello-world and let your user run… Beginner · Step by step · Linux Article Docker basics · Packages & updates 15 Oct 2026
- 0329 Docker CLI cheat sheet The Docker commands you reach for every day, grouped by what they act on: containers, images, volumes, networks, logs and cleanup, with… Beginner · Cheat sheet · Linux, macOS, Windows Article Docker basics 15 Oct 2026
Repos in the wild
- Watchtower (maintained fork): automatic container image updates nicholas-fedor/watchtower Watchtower watches your running containers, pulls newer versions of their images and restarts them with the same settings. This fork continues the project after the original containrrr repository was archived. GitHub
- Uptime Kuma: self-hosted uptime monitoring louislam/uptime-kuma Uptime Kuma is a self-hosted monitoring tool with a web UI that checks websites, TCP ports, DNS, Docker containers and more, draws uptime history and sends alerts. One container is all it needs. GitHub
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