Docker Cheatsheet

docker101.md

Why Docker?

• guarantee the software always run in the same way.

Get Started

• build docker build -t sample-node-image .
• run docker run -dp 3000:3000 sample-node-image

Update Source Code

• list: docker ps
• remove: docker rm -rf <container_id>
• rebuild: docker build -t sample-node-image .
• restart: docker run -dp 3000:3000 sample-node-image

Share Images

• create: a public repo in Docker Hub.
• login: docker login -u <USER_NAME>
• tag: docker tag sample-node-image <USER_NAME>/sample-node-image
• push: docker push <USER_NAME>/sample-node-image

Persist Data

Named Volume

• format: todo-db:/etc/todos
• use case:
  • location on host doesn't matter.
  • can be easily shared between containers.
  • eg: mongodb data persist on host.
• create: docker volume create todo-db
• run:docker run -dp 3000:3000 todo-db:/etc/todos sample-node-image
• inpect: docker volume inspect todo-db

version: "3.7"
  services:
    mysql:
        image: mysql:5.7
        volumes:
            - todo-mysql-data:/var/lib/mysql 

volumes:
    todo-mysql-data

Bind Volume

• format: /desktop/todo-app:/usr/local/app
• use case:
  • location on host matters
  • don't need to shared between containers
  • eg: watch development mode.
• create: docker run -dp 3000:3000 -w /app -v "$(pwd):/app" node:12-alpine sh -c "yarn install && yarn run dev"
  • -w /app: set working directory in container
  • -v "$(pwd):/app": bind host current directory to /app in the container

version: "3.7"

services:
  post-api:
    container_name: post_service
    build: ./
    command: yarn start
    volumes:
      - ./:/app

Logging

• inspect: docker logs -f <container_id>

Network

• create: docker network create todo-app
• connect: docker run --network todo-app --network-alias mysql
  • the network-alias will be the hostname of the container

version: "2.4"

services:
  proxy:
    build: ./proxy
    networks:
      - outside_network
      - default
  app:
    build: ./app
    networks:
      - default

networks:
  outside:
    external: true
    name: outside_network

Compose

• A tool used to define a complete application stack.

version: "3.7"
  services:
    app:
        image: node:12-alpine
        command: yarn installl && yarn run dev
        working_dir: /app
        volumes: ./:/app
        ports:
            - 3000:3000
        environment
            MYSQL_HOST: mysql
            MYSQL_USER: root
            MYSQL_PASSWORD: secret
            MYSQL_DB: todos
    mysql:
        image: mysql:5.7
        volumes:
            - todo-mysql-data:/var/lib/mysql
        environment:
            MYSQL_ROOT_PASSWORD: secret
            MYSQL_DATABASE: todos

volumes:
    todo-mysql-data

• start
  • docker-compose up -d
  • docker-compose --env-file .docker.development.env up -d
• log
  • docker logs -f <container_name>
  • docker-compose logs -f
  • docker-compose logs -f <service_name>
• remove
  • docker-compose down
  • docker-compose down --volumes delete volumes as well

Layer Cache

• inspect layers: docker image history getting-started
• every command create a new layer

FROM node:12-alpine
WORKDIR /app
COPY . .
RUN yarn install --production
CMD ["node","src/index.js"]

• problem:
  • when you udpate some dependencies, you need to rebuild this image.
  • line 1,2,5 is automatically cached.
  • but what about line 3 and 4?
  • everytime you update some dependencies, you also need to copy other files again
  • and you also copy files from host node_modules to the container.
• solution: separate unstable parts

# Dockerfile
FROM node:12-alpine
WORKDIR /app
COPY package.json yarn.lock ./
RUN yarn install --production
COPY . . # package.json change won't decache this one.
CMD ["node","src/index.js"]

• important!

# .dockerignore
node_modules # this is important

Multi-Stage Builds

• build stage: the image will be the latest stage.
• the final image only contains built code

FROM maven AS build
WORKDIR /app
COPY . .
RUN mvn package

FROM tomcat
COPY --from=build /app/target/file.war /usr/local/tomcat/webapps