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Docker

Docker cheat sheet with essential commands for containers, images, volumes, networks, Docker Compose, and orchestration examples.

10 min read
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Container Management

Running Containers

Start and run Docker containers with various options

bash
💡 Use -d for background containers
⚠️ Always name containers for easier management
📌 Use --rm for temporary containers
✅ Set resource limits in production

Container State Management

Control container lifecycle - start, stop, restart, and remove

bash
💡 docker ps -a shows stopped containers too
⚠️ Use -f flag carefully to force remove
📌 Container prune removes all stopped containers
✅ Always stop before removing unless using -f

Container Inspection & Logs

Debug and inspect running containers for troubleshooting

bash
💡 Use -f to follow logs in real-time
📌 docker exec -it for interactive sessions
⚡ Inspect with --format for specific fields
✅ Copy files without stopping container

Executing Commands in Containers

Run commands inside running containers with docker exec and copy files with docker cp

bash
💡 docker exec -it opens an interactive terminal — use sh for Alpine, bash for Debian/Ubuntu
⚡ Use docker cp to quickly grab log files or inject config without rebuilding
📌 docker stats shows live resource usage — essential for debugging memory/CPU issues
🟢 docker exec -d runs the command in the background without attaching to it
execcpdebug

Image Management

Building Images

Build Docker images from Dockerfiles with various options

bash
💡 Use .dockerignore to exclude files
⚡ BuildKit provides advanced features
📌 Multi-stage builds reduce image size
✅ Always tag images with versions

Image Operations

Manage Docker images - pull, push, tag, and remove

bash
💡 Use specific tags instead of latest
⚠️ Prune regularly to save disk space
📌 Save images for offline transfer
✅ Always login before pushing

Image Registry

Work with Docker registries and manage image distribution

bash
🔒 Always use HTTPS for production registries
💡 Tag images with registry URL
📌 Local registry useful for testing
✅ Implement authentication for private registries

Dockerfile

Write Dockerfiles to build custom images with all the key instructions

Dockerfile Instructions

The essential Dockerfile commands for building images

dockerfile
💡 Always use specific image tags (node:22-alpine) not "latest" — reproducible builds
⚡ Copy package.json first, then npm install, then copy source — maximizes Docker layer cache
📌 ARG is build-time only; ENV persists into the running container — know the difference
🟢 Run as a non-root USER in production — it only takes 2 lines and prevents privilege escalation
dockerfilebuildinstructions

Multi-Stage Builds

Use multiple FROM stages to create small, optimized production images

dockerfile
💡 Multi-stage builds keep dev tools (compilers, build deps) out of the final image
⚡ Go apps can use FROM scratch for the final stage — just the binary, ~10MB total
📌 COPY --from=stagename copies files from a previous stage into the current one
🟢 Use --target to build a specific stage: docker build --target build .
multi-stagebuildoptimization

.dockerignore

Exclude files from the build context to speed up builds and avoid leaking secrets

bash
💡 Without .dockerignore, Docker sends EVERYTHING in the directory to the build daemon
⚡ Always ignore node_modules — they get reinstalled with npm ci inside the image
📌 Ignore .env files to prevent secrets from being baked into the image
🟢 Same syntax as .gitignore — supports wildcards, negation (!important.md), and comments
dockerignorebuildsecurity

Volumes & Networks

Volume Management

Create and manage Docker volumes for persistent data storage

bash
💡 Named volumes persist data between containers
📌 Bind mounts for development, volumes for production
⚠️ Prune removes all unused volumes
✅ Backup important volumes regularly

Network Management

Configure Docker networks for container communication

bash
💡 Containers on same network can communicate by name
🔒 Use internal networks for security
📌 Bridge is default, overlay for Swarm
✅ Custom networks provide better isolation

Docker Compose

Compose Basics

Essential Docker Compose commands for multi-container applications

bash
💡 Use -d for background operation
⚡ --scale for horizontal scaling
📌 -f to specify custom compose files
✅ Always use down -v to clean volumes

Compose Configuration

Full compose.yml reference with depends_on, healthcheck, profiles, watch, and more

yaml
💡 depends_on with condition: service_healthy waits until the dependency passes its healthcheck
⚡ Compose Watch syncs files without rebuilding — use action: sync for source, action: rebuild for deps
📌 Profiles let you define optional services (debug tools, admin panels) that only start when requested
🟢 Use env_file to load .env files — keeps secrets out of compose.yml and version control

System & Cleanup

System Management

Monitor and manage Docker system resources and information

bash
💡 Regular pruning prevents disk issues
⚠️ Prune -a removes all unused images
📌 Use filters to control what gets pruned
✅ Monitor disk usage with system df

Debugging & Troubleshooting

Debug containers and resolve common Docker issues

bash
💡 nicolaka/netshoot has many network tools
🔍 Use --progress=plain for detailed build output
📌 Override entrypoint to debug failed containers
✅ Always check logs first when debugging