images

• recipe
  • tech
  • runtime
  • tools to run code
    containers
• output
• 1 image can create multiple container instances
• write server: must have index.js: app.get const port app.listen
• you write images in docker file
  • FROM …
  • WORKDIR …(similar to cd)
  • COPY package*.json ./ (copy package/package-lock if avaliable)
  • RUN npm install (install dependencies)
  • need to create .dockerignore to avoid hassle of the next step
    • node_modules
    • .env
    • your browser history
  • COPY . . (boom copy everything into container)
    • but we don’t want to copy node_modules
  • ENV PORT=xxxx (we can set environment variable in docker)
  • EXPOSE xxxx
  • run the app with
    • CMD ["npm","start"] (CMD to start the container)
• build image with docker build -t preferred_image_name .(location you want it to be)
• run container: docker run -p xxxx:xxxx preferred_image_name
  • -p : port forwarding from computer:docker_container
• docker compose
  • set up everything in one container is too painful
  • multi container application: if your project required backend, database, frontend, go separate them into many containers
  • but to do this, you need to run everything all at once, so, you need to connect them somehow
  • starts from create compose.yaml
  • docker compose up
  • docker compose down to close
• docker volume
  • docker wipe everything (state, data) when we close our containers
  • volume: dir that docker can access to save stuffs and share to other containers
• docker build cloud
  • x39 speed build time

docker init

• but you can get a basic template with docker init
  compose.yaml

services:
	backend:
		build: .
		ports: 
		- '9000:9000'
	db:
		image: postgres:latest
		environment:
			POSTGRES_USER: user
			POSTGRES_PASSWORD: pass
			POSTGRES_DB: mydb
		volumes:
			- postgres_data:/var/lib/postgersql/data
volumes:
	postgres_data:
	

docker commands

• docker —version
• docker exec (run via terminal if you don’t wanna run stuff via docker desktop)
• docker scout : good please do this to find
  • in GUI click at running image, click vulnerabilities, then click start analysis

created on: Sat Nov 29 2025