• Namespaces isolate resources within a K8s cluster.
• K8s creates a default namespace when the cluster is created. This default namespace is used to create resources.
• If the cluster is deployed using KubeAdmin, it also creates a namespace kube-system in which all the internal K8s resources are deployed.
• Resource limits can be placed at the namespace level. So, if we are using the same cluster for both dev and prod namespaces, we can place a resource limit on the dev namespace to prevent it from starving the prod namespace.

DNS Resolution

• Resources within a namespace can refer to each other by their names.
• For cross namespace communication, a resource needs to specify the namespace as shown below.

cluster.local - domain name for the cluster

svc - subdomain for service object

dev - namespace

db-service - service in the dev namespace

Creating a namespace

• Imperative command: k create namespace <namespace>

• Declarative manifest file

  apiVersion: v1
  kind: Namespace
  metadata:
  	name: dev
  

Creating resources in a namespace

• Command line: k apply -f pod.yml --namespace=dev (untracked)

• Config file (tracked): Use the namespace property under the metadata section. This will always create the resource in the specified namespace.

  metadata:
  	namespace: dev
  

Set namespace permanently