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wiki:ai:docker_cheatsheet [2026/01/06 15:43] – bgourleywiki:ai:docker_cheatsheet [2026/01/21 22:00] (current) – bgourley
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-**Docker Basics – Command Reference**+======Docker Basics – Command Reference======
  
-**Docker Installation and Health Checks**+====Docker Installation and Health Checks====
  
 **docker version** **docker version**
Line 30: Line 30:
 docker info docker info
  
-**Working With Containers**+====Working With Containers====
  
 **docker run** **docker run**
Line 97: Line 97:
 docker inspect my-container docker inspect my-container
  
-**Executing Commands in Running Containers**+====Executing Commands in Running Containers====
  
 **docker exec** **docker exec**
Line 114: Line 114:
 docker exec my-container ls /etc docker exec my-container ls /etc
  
-**Logs and Runtime Monitoring**+====Logs and Runtime Monitoring====
  
 **docker logs** **docker logs**
Line 140: Line 140:
 docker stats my-container docker stats my-container
  
-**Images and Registries**+====Images and Registries====
  
 **docker pull** **docker pull**
Line 183: Line 183:
 You must authenticate with the registry using docker login. You must authenticate with the registry using docker login.
  
-**Cleanup and Disk Management**+====Cleanup and Disk Management====
  
 **docker system df** **docker system df**
Line 227: Line 227:
 This removes all unused images and volumes and should be used with caution. This removes all unused images and volumes and should be used with caution.
  
-**Docker Contexts**+====Docker Contexts====
  
 **docker context ls** **docker context ls**
Line 246: Line 246:
  
 docker context use desktop-linux docker context use desktop-linux
 +
 +======Docker Networking Basics======
 +
 +====Docker Network Types====
 +
 +**Default bridge network**
 +
 +Purpose\\
 +Provides a private, NATed network for containers. Containers attached to the same bridge network can communicate using IP addresses. Name-based DNS resolution is limited on the default bridge.
 +
 +Notes\\
 +This is the network used when no --network flag is specified.
 +
 +Inspect the default bridge
 +
 +docker network inspect bridge
 +
 +Run a container on the default bridge
 +
 +docker run --rm alpine sh
 +
 +**Host network**
 +
 +Purpose\\
 +Shares the host network stack with the container.
 +
 +Notes\\
 +On macOS, Docker runs inside a virtual machine. As a result, --network host does not behave the same way it does on Linux and does not give direct access to the Mac’s network namespace.
 +
 +Run a container with host networking
 +
 +docker run --rm --network host alpine sh
 +
 +**None network**
 +
 +Purpose\\
 +Disables all networking for the container except the loopback interface.
 +
 +Run a container with no networking
 +
 +docker run --rm --network none alpine sh
 +
 +====Managing Docker Networks====
 +
 +**docker network ls**
 +
 +Purpose\\
 +Lists all Docker networks.
 +
 +Usage
 +
 +docker network ls
 +
 +**docker network inspect**
 +
 +Purpose\\
 +Displays detailed configuration and connected containers for a network.
 +
 +Usage
 +
 +docker network inspect ai-net
 +
 +**docker network create**
 +
 +Purpose\\
 +Creates a user-defined bridge network with built-in DNS resolution and isolation.
 +
 +Usage
 +
 +docker network create ai-net
 +
 +Notes\\
 +User-defined bridge networks are recommended for multi-container applications.
 +
 +**docker network rm**
 +
 +Purpose\\
 +Deletes a Docker network.
 +
 +Usage
 +
 +docker network rm ai-net
 +
 +====Running Containers on Networks====
 +
 +**Run container on a specific network**
 +
 +Purpose\\
 +Attaches a container to a specified network at startup.
 +
 +Usage
 +
 +docker run -d --name web --network ai-net nginx
 +
 +**docker network connect**
 +
 +Purpose\\
 +Connects an existing container to an additional network.
 +
 +Usage
 +
 +docker network connect other-net web
 +
 +Notes\\
 +Containers can be attached to multiple networks simultaneously.
 +
 +**Container DNS Resolution**
 +
 +Purpose\\
 +Allows containers on the same user-defined bridge network to resolve each other by name using Docker’s embedded DNS server.
 +
 +Test DNS resolution
 +
 +docker run --rm -it --network ai-net alpine sh -c "apk add --no-cache bind-tools && nslookup web"
 +
 +Inspect DNS configuration inside a container
 +
 +docker exec -it web cat /etc/resolv.conf
 +
 +Add a network alias
 +
 +docker network connect --alias websvc ai-net web
 +
 +**Port Publishing and Exposure**
 +
 +**-p flag**
 +
 +Purpose\\
 +Publishes a container port to the host, enabling host-to-container communication.
 +
 +Syntax
 +
 +-p <host_port>:<container_port>
 +
 +Example
 +
 +docker run -d --name web -p 8080:80 nginx
 +
 +Verify published ports
 +
 +docker ps
 +
 +docker port web
 +
 +Notes\\
 +Port publishing is not required for container-to-container communication on the same Docker network.
 +
 +====Container-to-Container Communication====
 +
 +**Same network communication**
 +
 +Purpose\\
 +Allows containers on the same network to communicate without published ports.
 +
 +Test connectivity
 +
 +docker run --rm -it --network ai-net nicolaka/netshoot sh -c "curl -I http:%%//%%web"
 +
 +**Cross-network isolation**
 +
 +Purpose\\
 +Demonstrates that containers on different networks cannot communicate by default.
 +
 +Test isolation
 +
 +docker run --rm -it --network other-net nicolaka/netshoot sh -c "curl -I http:%%//%%web || echo 'unreachable'"
 +
 +Connect container to multiple networks
 +
 +docker network connect other-net web
 +
 +Re-test connectivity
 +
 +docker run --rm -it --network other-net nicolaka/netshoot sh -c "curl -I http:%%//%%web"
 +
 +====Networking Diagnostics and Debugging====
 +
 +**Inspect container network settings**
 +
 +Purpose\\
 +Displays IP addresses, networks, and endpoints for a container.
 +
 +Usage
 +
 +docker inspect web
 +
 +**Use a diagnostic container**
 +
 +Purpose\\
 +Provides networking tools such as curl, ping, nslookup, and traceroute.
 +
 +Usage
 +
 +docker run --rm -it --network ai-net nicolaka/netshoot
 +
 +====Cleanup Networking Resources====
 +
 +**Remove containers**
 +
 +docker rm -f web client
 +
 +**Remove networks**
 +
 +docker network rm ai-net test-net other-net
 +
 +======Docker Volumes and Storage======
 +
 +====Volumes vs Bind Mounts vs tmpfs====
 +
 +**Concept Summary**
 +
 +Named volume
 +
 +  * Managed by Docker
 +  * Lives in Docker’s storage area
 +  * Best for persistent application data
 +
 +Bind mount
 +
 +  * Maps a host directory into the container
 +  * Best for development and live code editing
 +
 +tmpfs
 +
 +  * In-memory filesystem
 +  * Data is lost when the container stops
 +  * Best for temporary or sensitive data
 +
 +**Named volume example**
 +
 +Create a named volume:
 +
 +docker volume create myvol
 +
 +docker volume ls
 +
 +docker volume inspect myvol
 +
 +Run a container using the volume:
 +
 +docker run --rm -it -v myvol:/data alpine sh
 +
 +Inside the container:
 +
 +echo "hello from volume" > /data/file.txt
 +
 +ls /data
 +
 +exit
 +
 +Run another container with the same volume:
 +
 +docker run --rm -it -v myvol:/data alpine sh
 +
 +Inside:
 +
 +cat /data/file.txt
 +
 +exit
 +
 +What this demonstrates
 +
 +  * The volume persists after the first container exits.
 +  * A second container can read the same data.
 +  * Data is independent of any specific container.
 +
 +**Bind mount example (host directory)**
 +
 +Create a directory on the host:
 +
 +mkdir -p ~/docker-bind-test
 +
 +echo "hello from host" > ~/docker-bind-test/host.txt
 +
 +Run a container with a bind mount:
 +
 +docker run --rm -it \
 +
 +-v ~/docker-bind-test:/data \
 +
 +alpine sh
 +
 +Inside the container:
 +
 +ls /data
 +
 +echo "written from container" > /data/container.txt
 +
 +exit
 +
 +On the host:
 +
 +ls ~/docker-bind-test
 +
 +cat ~/docker-bind-test/container.txt
 +
 +What this demonstrates
 +
 +  * The container sees and modifies the host filesystem directly.
 +  * Changes on the host and in the container are immediately visible.
 +  * No rebuild is required to reflect code or data changes.
 +
 +**tmpfs example (in-memory)**
 +
 +Run a container with tmpfs:
 +
 +docker run --rm -it \
 +
 +--tmpfs /data:rw,size=64m \
 +
 +alpine sh
 +
 +Inside:
 +
 +echo "temp data" > /data/tmp.txt
 +
 +ls /data
 +
 +exit
 +
 +Run a new container:
 +
 +docker run --rm -it --tmpfs /data alpine sh -c "ls /data || echo empty"
 +
 +What this demonstrates
 +
 +  * Data stored in tmpfs disappears when the container stops.
 +  * Data never touches disk.
 +  * Storage is purely in memory.
 +
 +====Create and Manage Named Volumes====
 +
 +**Create and list volumes**
 +
 +docker volume create ai-data
 +
 +docker volume ls
 +
 +**Inspect volume metadata**
 +
 +docker volume inspect ai-data
 +
 +Look for:
 +
 +  * Driver type (usually local)
 +  * Mountpoint inside Docker’s storage
 +
 +**Use a volume and verify persistence**
 +
 +Write data into the volume:
 +
 +docker run --rm -it -v ai-data:/models alpine sh
 +
 +Inside:
 +
 +echo "model checkpoint v1" > /models/checkpoint.txt
 +
 +exit
 +
 +Verify persistence:
 +
 +docker run --rm -it -v ai-data:/models alpine sh -c "cat /models/checkpoint.txt"
 +
 +What this demonstrates
 +
 +  * Data written by one container is visible to future containers.
 +  * Volumes persist beyond container lifetimes.
 +
 +====Use Bind Mounts for Development====
 +
 +**Create a simple development file**
 +
 +On the host:
 +
 +mkdir -p ~/bind-dev
 +
 +cat > ~/bind-dev/app.py << 'EOF'
 +
 +print("version 1")
 +
 +EOF
 +
 +Run a Python container with bind mount:
 +
 +docker run --rm -it \
 +
 +-v ~/bind-dev:/app \
 +
 +python:3.12-slim \
 +
 +python /app/app.py
 +
 +Edit the file on the host:
 +
 +echo 'print("version 2")' >> ~/bind-dev/app.py
 +
 +Re-run the container:
 +
 +docker run --rm -it \
 +
 +-v ~/bind-dev:/app \
 +
 +python:3.12-slim \
 +
 +python /app/app.py
 +
 +What this demonstrates
 +
 +  * The container runs code directly from the host filesystem.
 +  * Code changes do not require rebuilding an image.
 +  * Ideal for iterative development workflows.
 +
 +====Share Volumes Between Containers====
 +
 +**Create a shared volume**
 +
 +docker volume create shared-vol
 +
 +**Writer container**
 +
 +Run:
 +
 +docker run --rm -it -v shared-vol:/shared alpine sh
 +
 +Inside:
 +
 +echo "written by writer" > /shared/data.txt
 +
 +exit
 +
 +**Reader container**
 +
 +Run:
 +
 +docker run --rm -it -v shared-vol:/shared alpine sh
 +
 +Inside:
 +
 +cat /shared/data.txt
 +
 +exit
 +
 +What this demonstrates
 +
 +  * Multiple containers can mount the same volume.
 +  * Data written by one container is immediately available to others.
 +  * Enables multi-stage pipelines and producer–consumer patterns.
 +
 +====Back Up and Restore Volume Data====
 +
 +**Back up a volume to a tar archive**
 +
 +Create a backup:
 +
 +docker run --rm \
 +
 +-v ai-data:/data \
 +
 +-v $(pwd):/backup \
 +
 +alpine \
 +
 +tar czf /backup/ai-data-backup.tar.gz -C /data .
 +
 +Verify:
 +
 +ls ai-data-backup.tar.gz
 +
 +What this does
 +
 +  * Mounts the volume at /data
 +  * Mounts the current host directory at /backup
 +  * Archives all volume contents into a file on the host
 +
 +**Simulate data loss**
 +
 +Delete and recreate the volume:
 +
 +docker volume rm ai-data
 +
 +docker volume create ai-data
 +
 +Check it is empty:
 +
 +docker run --rm -it -v ai-data:/models alpine sh -c "ls /models"
 +
 +**Restore from backup**
 +
 +Restore the data:
 +
 +docker run --rm \
 +
 +-v ai-data:/data \
 +
 +-v $(pwd):/backup \
 +
 +alpine \
 +
 +tar xzf /backup/ai-data-backup.tar.gz -C /data
 +
 +Verify:
 +
 +docker run --rm -it -v ai-data:/models alpine sh -c "cat /models/checkpoint.txt"
 +
 +What this demonstrates
 +
 +  * Volume data can be fully backed up and restored.
 +  * Volumes are portable across machines and environments.
 +
 +====Clean Up Unused Volumes====
 +
 +**List volumes**
 +
 +docker volume ls
 +
 +**Remove specific volumes**
 +
 +docker volume rm myvol shared-vol ai-data
 +
 +**Remove all unused volumes**
 +
 +docker volume prune
 +
 +**Inspect disk usage**
 +
 +docker system df -v
 +
 +What this demonstrates
 +
 +  * Volumes consume real disk space.
 +  * Unused volumes accumulate over time.
 +  * Regular cleanup prevents silent disk exhaustion.
 +======Docker Compose======
 +
 +====Overview====
 +
 +This reference documents the core Docker Compose commands used to:
 +
 +  * Build and run multi-container applications
 +  * Manage service dependencies
 +  * Configure health checks
 +  * Use environment files
 +  * Control application lifecycle
 +  * Scale services horizontally
 +
 +All commands assume:
 +
 +  * macOS with Docker Desktop
 +  * Docker Compose v2 (docker compose)
 +  * A project directory containing docker-compose.yml
 +
 +====Project Setup Commands====
 +
 +**mkdir and cd**
 +
 +Purpose\\
 +Creates and enters a new project directory for a Compose application.
 +
 +Usage
 +
 +mkdir compose-lab && cd compose-lab
 +
 +mkdir app
 +
 +What it does
 +
 +  * Creates a folder to hold all Compose-related files
 +  * Groups all containers, networks, and volumes under a single project name
 +  * Makes lifecycle management easier
 +
 +====Docker Compose Lifecycle Commands====
 +
 +**docker compose up**
 +
 +Purpose\\
 +Builds images (if needed) and starts all services defined in docker-compose.yml.
 +
 +Usage
 +
 +docker compose up
 +
 +docker compose up -d
 +
 +docker compose up -d --build
 +
 +Options
 +
 +  * -d runs services in the background (detached mode)
 +  * --build forces a rebuild of images before starting
 +
 +What it does
 +
 +  * Creates a default network for the project
 +  * Creates named volumes if missing
 +  * Builds images for services with build:
 +  * Starts containers in dependency order
 +  * Attaches logs to the terminal (unless -d is used)
 +
 +When to use
 +
 +  * Initial startup of the stack
 +  * After code or Dockerfile changes
 +  * For local testing and dev environments
 +
 +**docker compose down**
 +
 +Purpose\\
 +Stops and removes all services in the Compose project.
 +
 +Usage
 +
 +docker compose down
 +
 +docker compose down -v
 +
 +docker compose down --rmi local -v
 +
 +Options
 +
 +  * -v removes named volumes (destroys persistent data)
 +  * --rmi local removes images built by Compose
 +
 +What it does
 +
 +  * Stops all running containers
 +  * Deletes containers
 +  * Deletes the project network
 +  * Optionally deletes volumes and images
 +
 +When to use
 +
 +  * Resetting the environment
 +  * Freeing system resources
 +  * Recreating a clean stack
 +
 +**docker compose ps**
 +
 +Purpose\\
 +Lists the current status of services in the Compose project.
 +
 +Usage
 +
 +docker compose ps
 +
 +What it does
 +
 +  * Shows container names
 +  * Displays service states (running, exited, unhealthy)
 +  * Shows port mappings
 +  * Displays health status
 +
 +When to use
 +
 +  * Verify everything is running
 +  * Debug startup failures
 +  * Check healthcheck status
 +
 +**docker compose logs**
 +
 +Purpose\\
 +Displays logs from all services in the project.
 +
 +Usage
 +
 +docker compose logs
 +
 +docker compose logs -f
 +
 +docker compose logs api
 +
 +Options
 +
 +  * -f follows logs in real time
 +  * api limits output to a single service
 +
 +What it does
 +
 +  * Aggregates stdout and stderr from all containers
 +  * Prefixes logs with service names
 +  * Streams logs live when -f is used
 +
 +When to use
 +
 +  * Debug startup issues
 +  * Monitor API or database activity
 +  * Investigate crashes or errors
 +
 +====Build and Image Management====
 +
 +**docker compose build**
 +
 +Purpose\\
 +Builds images for services that specify a build: section.
 +
 +Usage
 +
 +docker compose build
 +
 +docker compose build api
 +
 +What it does
 +
 +  * Runs docker build for each service image
 +  * Tags images with project-specific names
 +  * Caches build layers between runs
 +
 +When to use
 +
 +  * Pre-build images before starting services
 +  * Debug Dockerfile changes
 +  * Speed up later docker compose up runs
 +
 +====Service Interaction Commands====
 +
 +**docker compose exec**
 +
 +Purpose\\
 +Runs a command inside a running service container.
 +
 +Usage
 +
 +docker compose exec api sh
 +
 +docker compose exec db psql -U composeuser compose_db
 +
 +What it does
 +
 +  * Executes a command in the target container
 +  * Attaches stdin/stdout for interactive use
 +  * Uses the existing running container
 +
 +When to use
 +
 +  * Debug inside containers
 +  * Inspect environment variables
 +  * Run admin tools (psql, bash, python)
 +
 +**docker compose stop**
 +
 +Purpose\\
 +Stops services without removing containers.
 +
 +Usage
 +
 +docker compose stop
 +
 +docker compose stop db
 +
 +What it does
 +
 +  * Sends a stop signal to containers
 +  * Keeps containers, networks, and volumes intact
 +
 +When to use
 +
 +  * Temporarily pausing services
 +  * Simulating outages
 +  * Preserving state for later restart
 +
 +**docker compose start**
 +
 +Purpose\\
 +Restarts stopped services.
 +
 +Usage
 +
 +docker compose start
 +
 +docker compose start db
 +
 +What it does
 +
 +  * Restarts previously stopped containers
 +  * Preserves container filesystem and volumes
 +
 +When to use
 +
 +  * Resuming paused services
 +  * Testing recovery behavior
 +  * Bringing a stack back online
 +
 +====Health and Inspection Commands====
 +
 +**docker inspect**
 +
 +Purpose\\
 +Displays low-level metadata about a container.
 +
 +Usage
 +
 +docker inspect compose-db
 +
 +docker inspect compose-api
 +
 +What it does
 +
 +  * Shows container config, networks, volumes
 +  * Displays health status and logs
 +  * Reveals failure reasons for unhealthy services
 +
 +When to use
 +
 +  * Debug healthcheck failures
 +  * Inspect network wiring
 +  * Validate volume mounts
 +
 +**docker compose exec env**
 +
 +Purpose\\
 +Displays environment variables inside a container.
 +
 +Usage
 +
 +docker compose exec api env | sort
 +
 +What it does
 +
 +  * Prints all environment variables
 +  * Confirms .env and env_file values are injected
 +
 +When to use
 +
 +  * Validate runtime configuration
 +  * Debug missing credentials
 +  * Confirm DB host/port values
 +
 +====Service Scaling====
 +
 +**docker compose up --scale**
 +
 +Purpose\\
 +Runs multiple instances of a service.
 +
 +Usage
 +
 +docker compose up -d --scale api=3
 +
 +What it does
 +
 +  * Starts additional containers for the service
 +  * Names them sequentially (api-1, api-2, api-3)
 +  * Attaches all replicas to the same network
 +
 +When to use
 +
 +  * Simulate horizontal scaling
 +  * Test concurrency handling
 +  * Prepare for load balancing setups
 +
 +Important limitation\\
 +Compose does not automatically load-balance traffic across replicas.\\
 +A reverse proxy (nginx, Traefik) is required for real traffic distribution.
 +
 +====Networking and Port Mapping====
 +
 +**curl http:%%//%%localhost:8080**
 +
 +Purpose\\
 +Tests connectivity from the host into a containerized service.
 +
 +Usage
 +
 +curl http:%%//%%localhost:8080/healthz
 +
 +curl http:%%//%%localhost:8080/readyz
 +
 +What it does
 +
 +  * Sends HTTP request to host port 8080
 +  * Docker forwards traffic into the API container
 +  * Validates networking and service health
 +
 +When to use
 +
 +  * Smoke testing APIs
 +  * Validating port publishing
 +  * Debugging networking issues
 +
 +====Cleanup and Reset Commands====
 +
 +**docker compose down -v**
 +
 +Purpose\\
 +Destroys the entire Compose environment including volumes.
 +
 +Usage
 +
 +docker compose down -v
 +
 +What it does
 +
 +  * Stops all containers
 +  * Deletes containers
 +  * Deletes networks
 +  * Deletes named volumes
 +  * Wipes database and persistent state
 +
 +When to use
 +
 +  * Full environment reset
 +  * Freeing disk space
 +  * Starting fresh
 +
 +**docker compose down --rmi local -v**
 +
 +Purpose\\
 +Removes everything created by Compose including images.
 +
 +Usage
 +
 +docker compose down --rmi local -v
 +
 +What it does
 +
 +  * Stops services
 +  * Deletes containers
 +  * Deletes networks
 +  * Deletes volumes
 +  * Deletes built images
 +
 +When to use
 +
 +  * Total teardown
 +  * Reclaiming disk space
 +  * Forcing clean rebuilds
 +
  
wiki/ai/docker_cheatsheet.1767714238.txt.gz · Last modified: by bgourley

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