---
id: mat-02-k8s-objects-and-getting-started
title: "Kubernetes Objects & Getting Started Locally"
---

# Kubernetes objects and getting started

## Declarative model (desired state)
Kubernetes is declarative:
- you declare the desired state in a manifest (YAML)
- you post it to the API server
- Kubernetes stores desired state
- controllers continuously reconcile current state to desired state

Example scenarios:
- desired replicas = 10, 2 fail → controller schedules 2 new replicas
- change replicas from 3 to 6 → controller schedules 3 more replicas
- update app version from 1.0 to 2.0 → controller rolls out 2.0 gradually and rolls back if needed

## Pods
A Pod is the atomic unit of scheduling in Kubernetes.
- simplest use: run one container per pod
- advanced: multiple containers in one pod share network stack (same IP), volumes, IPC/shared memory

Important:
- scale by increasing the number of pods, not containers inside a pod
- pod lifecycle is “brutal”: pods are replaced (immutable); they do not “come back” after death

## Deployments (controllers)
In practice you rarely deploy pods directly.
You use higher-level controllers such as Deployments to get:
- self-healing
- scaling
- rollouts/rollbacks

Common controller names you may encounter:
- Deployment
- DaemonSet
- StatefulSet

## Services
Pods are ephemeral (they can and will die).
Services provide a stable facade:
- stable DNS name
- load balancing
- “service discovery” style routing to healthy pods

## Getting Kubernetes locally: installers overview
Kubernetes is complex (control plane, etcd, kubelet, networking…). Installers help.

Examples of installers/distributions:
- K3s
- K3d (runs K3s in Docker)
- kind (Kubernetes in Docker)
- MicroK8s
- Minikube
- Docker Desktop (Windows/Mac)

## kubectl
kubectl is the CLI tool for controlling clusters via the API server.
Version rule of thumb:
- kubectl should be within one minor version of the cluster control plane.
Config:
- uses local kubeconfig file: ~/.kube/config
- supports switching between clusters

## K3d quick start
Create a cluster:
- k3d cluster create mycluster

Delete it:
- k3d cluster delete mycluster

Example verification commands:
- kubectl get nodes
- kubectl get pods --all-namespaces

## K3d complex setup
Example: 3 server nodes and 5 agent nodes:
- k3d cluster create complex -s 3 -a 5

K3d also supports a config file (useful for versioning and sharing setup).