spec defines the desired state of the object.

This is the most important part of any Kubernetes YAML.

—

Depends on the object:

• Pod → containers
• Deployment → replicas + pod template
• Service → ports + selector
• Volume → storage config

—

spec: containers: - name: nginx image: nginx

—

spec: replicas: 3 selector: matchLabels: app: web

—

spec = “what you want the system to achieve”

Example:

• “I want 3 running pods”
• “I want nginx container”
• “I want traffic exposed on port 80”

—

spec is the instruction set for Kubernetes reconciliation loop