1.4 K8s NameSpaces

Kubernetes creates three default namespaces at cluster setup:

• default: For general user workloads.

• kube-system: For internal Kubernetes components (like networking, DNS).

• kube-public: For resources accessible to all users.

• While small or learning environments can work within the default namespace, larger or production setups benefit from custom namespaces (e.g., dev, prod) to isolate resources, apply access policies, and manage resource quotas. This helps prevent accidental changes and ensures better organization and control.

• In Kubernetes, resources within the same namespace can communicate using just their names (e.g., a web pod can reach a DB service by using dbservice). To access services across namespaces, use the full DNS format: servicename.namespace.svc.cluster.local (e.g., dbservice.dev.svc.cluster.local). Kubernetes automatically creates these DNS entries, where cluster.local is the default cluster domain and svc indicates it’s a service.

NameSpace Commands (Click to Expand)

    kubectl get pods --namespace=kube-system

    (OR)

    kubectl get pods --all-namespaces  #getting pods in all namespaces

    kubectl create -f pod-definition.yml --namespace=dev

Pod Definition with Namespace

Pod Configuration (Click to Expand)

apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
namespace: dev
labels:
    app: myapp
    type: front-end
spec:
containers:
    - name: nginx-container
    image: nginx

    kubectl create namespace dev (OR)
    kubectl create -f namespace-dev.yml

Namespace Definition

Namespace Creation Definition (Click to Expand)

apiVersion: v1
kind: Namespace
metadata:
name: dev

Set Another Namespace As Default (Click to Expand)

• But what if we want to switch to the dev namespace permanently, so that we don't have to specify the --namespace option anymore?

kubectl config set-context $(kubectl config current-context) --namespace=dev

ResourceQuota Configuration (Click to Expand)

• To limit resources in a namespace, create a resource quota.

apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: dev
spec:
  hard:
    pods: "10"
    requests.cpu: "4"
    requests.memory: 5Gi
    limits.cpu: "10"
    limits.memory: 10Gi