DevOps Classroom notes 09/Jul/2025

Labels

• A label is a key value pair that can be applied to any kubernetnes object
• This can be used for querying objects
• To add labels in manifest, refer metadata section.
• Refer Here for official docs
• manifest

---
apiVersion: v1
kind: Pod
metadata:
  name: one
  labels:
    app: nginx
    env: dev
    project: learning
spec:
  containers:
    - name: web
      image: nginx
      resources:
        requests:
          cpu: 100m
          memory: 10M
        limits:
          cpu: 500m
          memory: 128M
---
apiVersion: v1
kind: Pod
metadata:
  name: two
  labels:
    app: nginx
    env: qa
    project: learning
spec:
  containers:
    - name: web
      image: nginx
      resources:
        requests:
          cpu: 100m
          memory: 10M
        limits:
          cpu: 500m
          memory: 128M
---
apiVersion: v1
kind: Pod
metadata:
  name: three
  labels:
    app: nginx
    env: uat
    project: learning
spec:
  containers:
    - name: web
      image: nginx
      resources:
        requests:
          cpu: 100m
          memory: 10M
        limits:
          cpu: 500m
          memory: 128M

• 
• Once labels are applied we can query them using selectors
• Selectors are of two types
  • Equality Based: Two major operations equals & not equals
  • Set Based:
    • in
    • notin
    • exists
    • doesnot exists
• Query using

kubectl get po
kubectl get po -l 'env = dev'
kubectl get po -l 'env in (dev,qa)'

Usecases

• My pod requires some service to be up & then it should start
  • types of containers in pod
• How to ensure pods are running
  • controller objects
    • replica set
    • deployments => zero down time & rollbacks
    • daemonset
• How to run batch jobs
  • Job
  • CronJob
• How about rather than static replicas i need dynamic => Autoscalers
• Load balancing/Service Interactions
  • Service
  • Ingress
  • Exposing the services to external world
    • Loadbalancers
    • Port forwarding
• Storage Solutions:
  • Persistent Volumes
  • Controller:
    • StatefulSet
• Configuration & Secrets
  • configmaps
  • secrets
  • vaults (secret vaults)
• Administrative:
  • backup
  • upgrade
  • Authentication & Authorization
  • Network policies
• Manifest => Static YAML , To enable Dyanmic YAML
  • HELM
  • Kustomize
• GitOps:
  • ArgoCD
• Troubleshooting: (Observability)
  • Monitor
  • Prometheus & Grafana
• Security:
• Service Mesh