Kubernetes Objects

Overview

• Kubernetes uses objects to represent state of cluster.
• What containerized applications are running (and on which node)
• The policies around how those applications behave, such as restart policies, upgrade and fault tolerance.
• Once you create the object the Cuba Reddy system will constantly work to ensure that object exists and maintain cluster's desired state
• Every Kubernetes object include two nested fields that govern the object conflguration and they are - Object Specification and the Object status.
• The specification, which we provide describes your desired state for the object- the characteristics that you want the object to have
• The status describes the actual state of the object and is supplied and updated by the Kubernetes system
• All objects are identified by a unique name and a UID

Basic Kubernets Objects

The basic humanities objects include -

1. Pod
2. Service
3. Volume
4. Namespaces
5. Replicaset
6. Secrets
7. ConfigMaps
8. Deployments
9. Jobs
10. Darmonsets

There are more than 200 Kubernetes objects.

Relationship between the objects

• Pod manages containers
• Replica set manages pods
• services expose pod processes to the outside world
• Configmaps and Secrets helps you configure pod

Representation

• It represents as JSON or YAML file.
• You create these and then push them to the Kubernetes API with kubectl

State of the object

• Replicas (2/2)
• Image (Tomcat/Ubuntu)
• Name
• Port
• Volume
• Startup
• Detached

Kubernetes object management

• The kubectl command line to support several different ways to create and manage kubernetes object

Declarative is about describing what you are trying to achieve, without instructing how to do it.

Imperative explicitly tells "how to accomplish it.