Docker-compose cheat sheet

#docker #cheatsheet #devops

A cheat sheet to create you docker-compose.yml version: '3.8'

Build the image

web:
  # build from Dockerfile
  build: .
  # alternative to use a folder with more than one Dockerfile:
  build:
    context: ./dir # path to Dockerfile
    dockerfile: Dockerfile.dev #name of the file
    target: dev # specify the target in a multi-stage build
  # build from image
  image: ubuntu
  image: ubuntu:14.04

Init

Run the service as PID 1. Set this option to true to enable this feature for the service.

services:
  web:
    image: alpine:latest
    init: true

Expose port

ports:
  - "3000"
  - "8000:80"  # guest:host
# expose ports to linked services (not to host)
expose: ["3000"]

Commands and Entrypoint

# command to execute
command: bundle exec thin -p 3000
command: [bundle, exec, thin, -p, 3000]

# override the entrypoint
entrypoint: /app/start.sh
entrypoint: [php, -d, vendor/bin/phpunit]

Environment variables

# environment vars
environment:
  RACK_ENV: development
environment:
  - RACK_ENV=development

# environment vars from file
env_file: .env
env_file: [.env, .development.env]

Health check

# declare service healthy when `test` command succeed
healthcheck:
  test: ["CMD", "curl", "-f", "http://localhost"]
  interval: 1m30s
  timeout: 10s
  retries: 3
  start_period: 40s

Dependencies

# make sure `db` is alive before starting
depends_on:
  - db


# make sure `db` is healthy before starting
# and db-init completed without failure
depends_on:
db:
  condition: service_healthy
db-init:
  condition: service_completed_successfully

Volumes

volumes:
  - /var/lib/mysql # anonimous volume
  - ./host_path:/docker_container_path # bind mount

volumes:
  - type: bind
    source: ./host_path
    target: /docker_container_path
  - type: volume
    # no source. Override the previous volumes for a specific path 
    target: /node_modules

Restart

# automatically restart container
restart: unless-stopped
# always, on-failure, no (default)

User

# specifying user
user: root

# specifying both user and group with ids
user: 0:0

Commands

# Starts existing containers.
docker-compose start

# Stops running containers.
docker-compose stop

# Pauses running containers.
docker-compose pause

# Unpauses paused.
docker-compose unpause

# Lists containers.
docker-compose ps

# Builds, (re)creates, starts, and attaches to containers for a service.
docker-compose up

# Stops and removes containers.
docker-compose down