Kubernetes Demystified: YAML Tutorial for DevOps

What is YAML?

YAML is a data serialization language, like XML and JSON.

What is a serialization language?

Applications written with different technologies and languages, which have different data structures, can transfer data to each other on a common grid or standard format.

Ex: JSON, YAML, XML.

YAML is not — yet another markup language.

• "Human friendly" data serialization standard for all programming languages
• Syntax: strict indentation
• Store the config file with your code, or in its own git repo.

File extension: .yaml and .yml

YAML Format Compared to Others:

• Human readable and intuitive
• Line separation & indentation
• YAML use cases: Docker Compose files, Docker, Kubernetes, Ansible, Prometheus — a great fit for writing configuration files for all these recent DevOps tools

YAML identification:

• Line separation
• Indentation

YAML vs XML vs JSON
YAML is a superset of JSON — any valid JSON file is also a valid YAML file.

Basic Syntax of YAML:

Key Value Pairs:

# Comment use
app: user-authentication
port: 9000
version: 1.7

Objects:

By indenting the key value pair and indenting by objects:

microservice:
  app: user-authentication
  port: 9000
  version: 1.7

Lists:

microservice:
  - app: user-authentication
  port: 9000
  version: 1.7

Boolean Values:

microservice:
  - app: user-authentication
  port: 9000
  version: 1.7
  deploy: yes, no, on, off, false, true

More Lists:

microservice:
  - app: user-authentication
    version: [1.7, 2.1, 8.1]   # → string
  port: 9000

Kubernetes YAML Files:

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  containers:
    - name: nginx-container
      image: nginx
      ports:
        - containerPort: 80
      volumeMounts:
        - name: nginx-vol
          mountPath: /usr/nginx/html

Key value pairs breakdown:

• metadata = object
• labels = object
• spec = object
• containers = list of objects
• port = list
• volumeMounts = list of objects