# A Deployment describes a desired state ("I want 1 copy of nginx running,
# serving this ConfigMap's index.html") and hands it to Kubernetes, whose
# job is to continuously make reality match that description. If the Pod
# crashes, Kubernetes restarts it. If the node dies, Kubernetes (given more
# than one node — see docs/09-growing-up.md) reschedules it elsewhere.
# You never tell Kubernetes "start a container" directly; you describe the
# end state and it does the work. This is what "declarative" means.
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo
  namespace: demo
spec:
  replicas: 1
  selector:
    # Tells the Deployment which Pods belong to it. Must match
    # spec.template.metadata.labels below, or Kubernetes won't know
    # this Deployment owns the Pods it creates.
    matchLabels:
      app: demo
  template:
    metadata:
      labels:
        app: demo
    spec:
      containers:
        - name: nginx
          image: nginx:1.27-alpine
          ports:
            - containerPort: 80
          volumeMounts:
            # Mounts the ConfigMap's index.html over nginx's default page.
            - name: page
              mountPath: /usr/share/nginx/html
      volumes:
        - name: page
          configMap:
            name: demo-page