DevOps Classroom notes 18/Dec/2025

YAML

• This is Data description language.
• YAML uses name-value (key value) just like json
• Value can be of different forms
  • simple
    • text
    • number
    • boolean
  • complex
    • list/array (plural)
    • map/object
• syntax: YAML is heavily inspired by python (indentation) <name>: <value>
  • text: name: Avatar Fire and Ash
  • number: runtime: 197
  • boolean: imax: True or imax: yes
  • list:
    “`yaml
    story:</li>
    <li>James Cameron</li>
    <li>Amanda Silver</li>
    <li>Josh Friedman
    “`
  • map/object
    yaml
cast:
hero: Jake sully
heroin: Neytri
• Yaml files generally created with extensions .yaml or .yml

---
name: Avatar Fire and Ash
runtime: 197
director: James Cameron
imax: yes
story:
  - James Cameron
  - Amanda Silver
  - Josh Friedman
cast:
  hero: Jake sully
  heroin: Neytri

• Use any yaml validator Refer Here
• When we use yaml as an input to some tool, they would have defined schema.

Docker compose yaml file

• Compose file gives a reference Refer Here
• services are containers
• This will start postgres database and pgadmin
• I want both of them running a same network
• postgres container requires a volume
• postgres container will run of 5432 and pgamin will be hosted on 80 which will be mapped to 9080
• create a file called docker-compose.yml

---
services:
  pgadmin:
    image: dpage/pgadmin4
    networks:
      - pg-net
    environment:
      - PGADMIN_DEFAULT_EMAIL=admin@example.com
      - PGADMIN_DEFAULT_PASSWORD=admin123
    ports:
      - "32780:80"
    depends_on:
      - db
  db:
    image: postgres:16
    networks:
      - pg-net
    environment:
      - POSTGRES_DB=appdb
      - POSTGRES_USER=appuser
      - POSTGRES_PASSWORD=apppassword
    volumes:
      - pgdata:/var/lib/postgresql/data
networks:
  pg-net:
    name: pg-net
    driver: bridge

volumes:
  pgdata: