Docker Cheatsheet #docker #cheatsheet

docker-compose.yml

version: "3"
services:
  web:
    # replace username/repo:tag with your name and image details
    image: username/repo:tag
    deploy:
      replicas: 5
      resources:
        limits:
          cpus: "0.1"
          memory: 50M
      restart_policy:
        condition: on-failure
    ports:
      - "80:80"
    networks:
      - webnet
networks:
  webnet:

DOCKER.md

Docker cheatsheet

Terminology

Image -> Container (called Task if it's in a Service) -> Service -> Stack -> Swarm

• Image: An ordered collection of root filesystem changes and the corresponding execution parameters for use within a container runtime. Portable Docker images are defined by something called a Dockerfile.
• Container: A container is a runtime instance of a docker image.
• Service: A service is the definition of how you want to run your application containers in a swarm (a.k.a.: containers in production). At the most basic level a service defines which container image to run in the swarm and which commands to run in the container. To define, run, and scale services just write a docker-compose.yml file.
• Task: A single container running in a service is called a task.
• Swarm: A swarm is a group of machines that are running Docker and joined into a cluster.
• Node: The machines in a swarm can be physical or virtual. After joining a swarm, they are referred to as nodes.

Images and containers

Reference: Dockerizing a Node.js web app

Command	Description
docker image ls	List images in the local registry
docker build -t username/repo:tag .	Build Docker image
docker images	List images
docker run -p 49160:8080 -d username/repo:tag	Run image
docker ps	List containers
docker stop containerId	Stop running container
docker push username/repo:tag	Push image to Docker Hub

Services and tasks

Reference: Get Started, Part 3: Services

Command	Description
docker swarm init	Initialize a swarm
docker stack deploy -c docker-compose.yml appname	Deploy a new stack or update an existing stack
docker stack rm appname	Take stack down
docker swarm leave --force	Take swarm down
docker service ls	List services
docker service ps getstartedlab_web	List tasks

Swarms

Just remember that only swarm managers like myvm1 execute Docker commands; workers are just for capacity. Let's deploy the app on a swarm cluster.

Command	Description
docker swarm init	Initialize a swarm
docker-machine create --driver virtualbox myvm1	Create a Virtual Machine
docker-machine ls	List Virtual Machines
docker-machine ssh <myvm1> "docker swarm init --advertise-addr <myvm1 ip>"	Command VM to become a swarm manager
docker-machine ssh myvm1 "docker node ls"	List nodes in the swarm managed by myvm1
docker swarm leave	Leave swarm (node)
docker-machine env myvm1	Get command to configure shell to talk to VM
eval $(docker-machine env myvm1)	Configure shell to talk to VM (macOS)
docker stack deploy -c docker-compose.yml appname	Deploy the app on current machine (VM)
docker stack ps appname	List tasks
eval $(docker-machine env -u)	Unset docker-machine environment vars in current shell
docker-machine start <machine-name>	Restart machine
docker swarm join-token worker	Get join-token of current swarm for workers (issued by manager

Dockerfile

# Dockerfile for a Node.js application
FROM node:carbon

# Create app directory
WORKDIR /usr/src/app

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ./

RUN npm install
# If you are building your code for production
# RUN npm install --only=production

# Bundle app source
COPY . .

EXPOSE 8080
CMD [ "npm", "start" ]