Master Kubernetes from Scratch: Part 5 - Understanding Namespaces

Introduction to Namespaces

What are Namespaces?

Namespaces divide a Kubernetes cluster into smaller virtual clusters. They help organize and manage resources. This is useful when multiple teams, applications, or environments share one cluster.

Namespaces create logical partitions within a cluster. By default, Kubernetes places resources in the default Namespace unless you specify otherwise.

For example, if your organization has multiple teams like finance, HR, and corporate-ops, you could create namespaces matching each team's structure:

• finance

• hr

• corporate-ops

Teams can work independently without interfering with each other.

Key Characteristics of Namespaces

1. Soft Isolation: Namespaces provide logical boundaries, but not complete isolation.

2. Shared Cluster Resources: All Namespaces share the same cluster's nodes, storage, and network.

3. Organizational Flexibility: Namespaces simplify managing multiple tenants, which can include teams, applications, or customers.

For stronger isolation (hard tenancy), you need separate clusters on dedicated hardware.

Commands for Managing Namespaces

Creating a Namespace
You can create Namespaces imperatively or declaratively.

• Imperatively:

$ kubectl create ns learning-k8s

• Declaratively:
  Create a YAML file (e.g., learning-k8s-ns.yml):

kind: Namespace
apiVersion: v1
metadata:
  name: learning-k8s
  labels:
    env: demo

Then you can apply it:

$ kubectl apply -f learning-k8s-ns.yml

Listing Namespaces

$ kubectl get ns  
$ kubectl describe ns default  # provides detailed ns information

Deleting a Namespace

$ kubectl delete ns learning-k8s

Set a Default Namespace for Commands
Constantly adding -n or --namespace to every command can be tedious. Use this command to set a default Namespace for your session:

$ kubectl config set-context --current --namespace learning-k8s

Reset it after deleting a Namespace:

$ kubectl config set-context --current --namespace default

Deploying Resources to a Namespace

• Imperative Deployment
  Add the -n or --namespace flag to commands:

$ kubectl create deployment myapp --image=nginx -n learning-k8s

• Declarative Deployment
  Define the Namespace in the resource's YAML file:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  namespace: learning-k8s
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx

Apply it:

$ kubectl apply -f myapp.yml

Conclusion

In this chapter, you got familiar with the concept of Namespaces. They are lightweight and offer flexibility but do not provide strong isolation. If you need to isolate workloads completely, consider using multiple clusters.