docker-management

name docker-management description Manage Docker containers, images, volumes, and Compose. version 1.0.0 author sprmn24 license MIT platforms ["linux","macos","windows"] metadata {"hermes":{"tags":["docker","containers","devops","infrastructure","compose","images","volumes","networks","debugging"],"category":"devops","requires_toolsets":["terminal"]}} Docker Management Manage Docker containers, images, volumes, networks, and Compose stacks using standard Docker CLI commands. No additional dependencies beyond Docker itself. When to Use Run, stop, restart, remove, or inspect containers Build, pull, push, tag, or clean up Docker images Work with Docker Compose (multi-service stacks) Manage volumes or networks Debug a crashing container or analyze logs Check Docker disk usage or free up space Review or optimize a Dockerfile Prerequisites Docker Engine installed and running User added to the docker group (or use sudo ) Docker Compose v2 (included with modern Docker installations) Quick check: docker --version && docker compose version Quick Reference Task Command Run container (background) docker run -d --name NAME IMAGE Stop + remove docker stop NAME && docker rm NAME View logs (follow) docker logs --tail 50 -f NAME Shell into container docker exec -it NAME /bin/sh List all containers docker ps -a Build image docker build -t TAG . Compose up docker compose up -d Compose down docker compose down Disk usage docker system df Cleanup dangling docker image prune && docker container prune Procedure 1. Identify the domain Figure out which area the request falls into: Container lifecycle → run, stop, start, restart, rm, pause/unpause Container interaction → exec, cp, logs, inspect, stats Image management → build, pull, push, tag, rmi, save/load Docker Compose → up, down, ps, logs, exec, build, config Volumes & networks → create, inspect, rm, prune, connect Troubleshooting → log analysis, exit codes, resource issues 2. Container operations Run a new container: # Detached service with port mapping docker run -d --name web -p 8080:80 nginx # With environment variables docker run -d -e POSTGRES_PASSWORD=secret -e POSTGRES_DB=mydb --name db postgres:16 # With persistent data (named volume) docker run -d -v pgdata:/var/lib/postgresql/data --name db postgres:16 # For development (bind mount source code) docker run -d -v $( pwd )/src:/app/src -p 3000:3000 --name dev my-app # Interactive debugging (auto-remove on exit) docker run -it -- rm ubuntu:22.04 /bin/bash # With resource limits and restart policy docker run -d --memory=512m --cpus=1.5 --restart=unless-stopped --name app my-app Key flags: -d detached, -it interactive+tty, --rm auto-remove, -p port (host:container), -e env var, -v volume, --name name, --restart restart policy. Manage running containers: docker ps # running containers docker ps -a # all (including stopped) docker stop NAME # graceful stop docker start NAME # start stopped container docker restart NAME # stop + start docker rm NAME # remove stopped container docker rm -f NAME # force remove running container docker container prune # remove ALL stopped containers Interact with containers: docker exec -it NAME /bin/sh # shell access (use /bin/bash if available) docker exec NAME env # view environment variables docker exec -u root NAME apt update # run as specific user docker logs -- tail 100 -f NAME # follow last 100 lines docker logs --since 2h NAME # logs from last 2 hours docker cp NAME:/path/file ./local # copy file from container docker cp ./file NAME:/path/ # copy file to container docker inspect NAME # full container details (JSON) docker stats --no-stream # resource usage snapshot docker top NAME # running processes 3. Image management # Build docker build -t my-app:latest . docker build -t my-app:prod -f Dockerfile.prod . docker build --no-cache -t my-app . # clean rebuild DOCKER_BUILDKIT=1 docker build -t my-app . # faster with BuildKit # Pull and push docker pull node:20-alpine docker login ghcr.io docker tag my-app:latest registry/my-app:v1.0 docker push registry/my-app:v1.0 # Inspect docker images # list local images docker history IMAGE # see layers docker inspect IMAGE # full details # Cleanup docker image prune # remove dangling (untagged) images docker image prune -a # remove ALL unused images (careful!) docker image prune -a --filter "until=168h" # unused images older than 7 days 4. Docker Compose # Start/stop docker compose up -d # start all services detached docker compose up -d --build # rebuild images before starting docker compose down # stop and remove containers docker compose down -v # also remove volumes (DESTROYS DATA) # Monitoring docker compose ps # list services docker compose logs -f api # follow logs for specific service docker compose logs -- tail 50 # last 50 lines all services # Interaction docker compose exec api /bin/sh # shell into running service docker compose run -- rm api npm test # one-off command (new container) docker compose restart api # restart specific service # Validation docker compose config # validate and view resolved config Minimal compose.yml example: services: api: build: . ports: - "3000:3000" environment: # Password comes from the POSTGRES_PASSWORD secret, not the URL - DATABASE_URL=postgres://mydb_user@db:5432/mydb depends_on: db: condition: service_healthy db: image: postgres:16-alpine environment: POSTGRES_USER: user POSTGRES_PASSWORD: pass POSTGRES_DB: mydb volumes: - pgdata:/var/lib/postgresql/data healthcheck: test: [ "CMD-SHELL" , "pg_isready -U user" ] interval: 10s timeout: 5s retries: 5 volumes: pgdata: 5. Volumes and networks # Volumes docker volume ls # list volumes docker volume create mydata # create named volume docker volume inspect mydata # details (mount point, etc.) docker volume rm mydata # remove (fails if in use) docker volume prune # remove unused volumes # Networks docker network ls # list networks docker network create mynet # create bridge network docker network inspect mynet # details (connected containers) docker network connect mynet NAME # attach container to network docker network disconnect mynet NAME # detach container docker network rm mynet # remove network docker network prune # remove unused networks 6. Disk usage and cleanup Always start with a diagnostic before cleaning: # Check what's using space docker system df # summary docker system df -v # detailed breakdown # Targeted cleanup (safe) docker container prune # stopped containers docker image prune # dangling images docker volume prune # unused volumes docker network prune # unused networks # Aggressive cleanup (confirm with user first!) docker system prune # containers + images + networks docker system prune -a # also unused images docker system prune -a --volumes # EVERYTHING — named volumes too Warning: Never run docker system prune -a --volumes without confirming with the user. This removes named volumes with potentially important data. Pitfalls Problem Cause Fix Container exits immediately Main process finished or crashed Check docker logs NAME , try docker run -it --entrypoint /bin/sh IMAGE "port is already allocated" Another process using that port docker ps or lsof -i :PORT to find it "no space left on device" Docker disk full docker system df then targeted prune Can't connect to container App binds to 127.0.0.1 inside container App must bind to 0.0.0.0 , check -p mapping Permission denied on volume UID/GID mismatch host vs container Use --user $(id -u):$(id -g) or fix permissions Compose services can't reach each other Wrong network or service name Services use service name as hostname, check docker compose config Build cache not working Layer order wrong in Dockerfile Put rarely-changing layers first (deps before source code) Image too large No multi-stage build, no .dockerignore Use multi-stage builds, add .dockerignore Verification After any Docker operation, verify the result: Container started? → docker ps (check status is "Up") Logs clean? → docker logs --tail 20 NAME (no errors) Port accessible? → curl -s http://localhost:PORT or docker port NAME Image built? → docker images | grep TAG Compose stack healthy? → docker compose ps (all services "running" or "healthy") Disk freed? → docker system df (compare before/after) Dockerfile Optimization Tips When reviewing or creating a Dockerfile, suggest these improvements: Multi-stage builds — separate build environment from runtime to reduce final image size Layer ordering — put dependencies before source code so changes don't invalidate cached layers Combine RUN commands — fewer layers, smaller image Use .dockerignore — exclude node_modules , .git , __pycache__ , etc. Pin base image versions — node:20-alpine not node:latest Run as non-root — add USER instruction for security Use slim/alpine bases — python:3.12-slim not python:3.12