Quick References #

Docker Cleanup (Memory Management) #

#!/usr/bin/env bash
set -x
docker stop $(docker ps -a -q)
yes | docker system prune
yes | docker system prune --volumes
docker rm $(docker ps -a -q)
docker images -q --filter "dangling=true" | xargs docker rmi
docker rmi $(docker images -q)

Docker container and image cleanup #

docker images -f dangling=true -q | xargs docker rmi || true

Get IP Address of Docker image #

docker inspect --format '{{ .NetworkSettings.Networks.IPAddress }}' imagename

Docker Troubleshooting #

Docker logs command, as shown here:

docker logs --details containername

Delete all untagged images #

docker rmi $(docker images -q --filter "dangling=true") -f

Docker shell into alpine container #

docker run -it --rm alpine /bin/ash

Docker shell into debian container #

docker exec -it container_id /bin/bash

Remove all stopped containers #

docker container prune

Docker Compose #

Docker file example #

version: "3.9"
services:

  redis:
    image: redis:alpine
    ports:
      - "6379"
    networks:
      - frontend
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  db:
    image: postgres:9.4
    volumes:
      - db-data:/var/lib/postgresql/data
    networks:
      - backend
    deploy:
      placement:
        max_replicas_per_node: 1
        constraints:
          - "node.role==manager"

  vote:
    image: dockersamples/examplevotingapp_vote:before
    ports:
      - "5000:80"
    networks:
      - frontend
    depends_on:
      - redis
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
      restart_policy:
        condition: on-failure

  result:
    image: dockersamples/examplevotingapp_result:before
    ports:
      - "5001:80"
    networks:
      - backend
    depends_on:
      - db
    deploy:
      replicas: 1
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  worker:
    image: dockersamples/examplevotingapp_worker
    networks:
      - frontend
      - backend
    deploy:
      mode: replicated
      replicas: 1
      labels: [APP=VOTING]
      restart_policy:
        condition: on-failure
        delay: 10s
        max_attempts: 3
        window: 120s
      placement:
        constraints:
          - "node.role==manager"

  visualizer:
    image: dockersamples/visualizer:stable
    ports:
      - "8080:8080"
    stop_grace_period: 1m30s
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    deploy:
      placement:
        constraints:
          - "node.role==manager"

networks:
  frontend:
  backend:

volumes:
  db-data:

Build #

version: "3.9"
services:
  webapp:
    build: ./dir

version: "3.9"
services:
  webapp:
    build:
      context: ./dir
      dockerfile: Dockerfile-alternate
      args:
        buildno: 1

Dockerfile #

build:
  context: .
  dockerfile: Dockerfile-alternate

ARGS #

ARG buildno
ARG gitcommithash

RUN echo "Build number: $buildno"
RUN echo "Based on commit: $gitcommithash"

build:
  context: .
  args:
    buildno: 1
    gitcommithash: cdc3b19

build:
  context: .
  args:
    - buildno=1
    - gitcommithash=cdc3b19

YAML boolean values (“true”, “false”, “yes”, “no”, “on”, “off”) must be enclosed in quotes, so that the parser interprets them as strings.

command #

Override the default command.

command: bundle exec thin -p 3000

command: ["bundle", "exec", "thin", "-p", "3000"]

credential_spec #

version: "3.9"
services:
  myservice:
    image: myimage:latest
    credential_spec:
      config: my_credential_spec

configs:
  my_credentials_spec:
    file: ./my-credential-spec.json|

depends_on #

version: "3.9"
services:
  web:
    build: .
    depends_on:
      - db
      - redis
  redis:
    image: redis
  db:
    image: postgres

LABELS #

version: "3.9"
services:
  web:
    image: web
    deploy:
      labels:
        com.example.description: "This label will appear on the web service"

entrypoint #

entrypoint: /code/entrypoint.sh

entrypoint: ["php", "-d", "memory_limit=-1", "vendor/bin/phpunit"]

env_file #

env_file: .env

env_file:
  - ./common.env
  - ./apps/web.env
  - /opt/runtime_opts.env

environment #

environment:
  RACK_ENV: development
  SHOW: 'true'
  SESSION_SECRET:

environment:
  - RACK_ENV=development
  - SHOW=true
  - SESSION_SECRET

external_links #

Link to containers started outside this docker-compose.yml or even outside of Compose, especially for containers that provide shared or common services. external_links follow semantics similar to the legacy option links when specifying both the container name and the link alias (CONTAINER:ALIAS).

external_links:
  - redis_1
  - project_db_1:mysql
  - project_db_1:postgresql

extra_hosts #

extra_hosts:
  - "somehost:162.242.195.82"
  - "otherhost:50.31.209.229"

restart #

restart: "no"
restart: always
restart: on-failure
restart: unless-stopped

Volume configuration reference #

version: "3.9"

services:
  db:
    image: db
    volumes:
      - data-volume:/var/lib/db
  backup:
    image: backup-service
    volumes:
      - data-volume:/var/lib/backup/data

volumes:
  data-volume: