Docker cheat sheets
Docker packages an application and its dependencies into a lightweight container that runs identically anywhere. Three concepts sit under every command: an image (the immutable template), a container (a running instance of an image) and a volume (persistent storage that survives the container). Core commands covers the loop — run, ps, exec, logs, build — and the docker run flags you actually need. Docker Compose covers the compose.yaml file and the docker compose commands for multi-container apps. Cleanup & disk covers pruning images, containers, volumes and build cache — the part most people learn the hard way.
Every command is verified against the official Docker documentation and behaves identically on Docker Desktop (Windows/macOS) and Docker Engine (Linux). Two facts worth knowing up front: docker compose (no hyphen) is the current V2 plugin command — the old docker-compose V1 binary is deprecated — and stopped containers and dangling images quietly pile up until you prune them.
Cheat sheets
Core commands
run, ps, exec, logs, build and the docker run flags — the container lifecycle you type daily.
Docker Compose
The compose.yaml file and the docker compose commands for multi-container apps and services.
Cleanup & disk
Reclaim disk: system df, prune (system/image/container/volume), and removing dangling images.
Network tools
Subnet CalculatorIPv6 CalculatorWildcard MaskRange → CIDRSplitterAggregatorVLSM CalculatorPracticeCheat Sheet
FAQ
What is Docker?
Docker is a platform for packaging applications into containers — lightweight, isolated environments that bundle an app with its dependencies and run identically on any host. Unlike a virtual machine, a container shares the host's kernel, so it starts in seconds and uses a fraction of the resources. Docker's three core objects are images (immutable templates), containers (running instances) and volumes (persistent data).
What is the difference between Docker and a virtual machine?
A virtual machine runs a full guest operating system on a hypervisor, each with its own kernel, so it is heavy and slow to boot. A container shares the host kernel and only isolates the application's userspace, so it starts in milliseconds and costs far less memory and disk. Containers give you process-level isolation, not hardware-level isolation.
What is Docker Compose for?
Compose lets you define a multi-container application (a web server plus a database plus a cache, for example) in one declarative compose.yaml file and manage the whole stack with docker compose up / down / logs. Without Compose you would string together many docker run commands by hand.
Where do I find images to run?
Docker Hub (hub.docker.com) is the default public registry, hosting official images for nginx, postgres, redis, node, python and thousands of others. docker pull