Completek8s Classroomnotes 08/Aug/2023

Pod Contd…

• Pod has 3 types of containers
  • containers: (Our main application)
  • init containers: (Preconditions or Prep)
  • ephemeral containers (to be discussed later)

Labeling and annoting the Pods

• Labels are key/value pairs that you can attach to created objects and later use these labels for querying objects
  
• k8s also uses another type of metadata called Annotations. Annotations are very similar to labels (they alsor are key/value pairs).
  • Labels are intended to identify resources
  • Annotations are used to provide contextual information to the resource to be used by cluster or third party tools
• Refer Here for labels docs and Refer Here for annotations

Exercise

• Create a Pod with
  • labels:
    • env: dev
    • tier: backend
  • image: nginx
  • name: business-dev
• Create a Pod with
  • labels:
    • env: prod
    • tier: backend
  • image: nginx
  • name: business
• Create a Pod with
  • labels:
    • env: dev
    • tier: frontend
  • image: httpd
  • name: web-dev
• Create a Pod with
  • labels:
    • env: prod
    • tier: frontend
  • image: httpd
  • name: web
• Refer Here for the specs.
• Now create all the pods
  
• Labels can be queried using selectors Refer Here
  
• In Kubernetes we have objects which maintain Pods as part of their desired state
  • Job
  • CronJob
  • DaemonSet
  • ReplicaSet
  • ReplicationController
  • Deployment
  • StatefulSet

ReplicaSet

• ReplicaSet is a kubernetes object which allows us to run replicas of pods
• In the Desired state, we mention
  • number of replicas
  • PodSpecification
• Refer Here for the replicaset added
  

Exercise

• Do the same by using imperative syntaxes
• Figure out the differences between ReplicaSet and ReplicationController