Namespaces

Namespaces in Kubernetes are a way to divide cluster resources between multiple users or teams. They provide a mechanism for isolating resources and managing access control.

Example Namespace Definition

apiVersion: v1
kind: Namespace
metadata: 
  name: dev

Example Pod within a Namespace

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

Creating a Namespace

To create a new namespace, you can use the following command:

kubectl create namespace dev

Listing Namespaces

To list all namespaces in the cluster, use:

kubectl get namespaces

Deleting a Namespace

To delete a namespace and all its resources, use:

kubectl delete namespace dev

This command will remove the specified namespace and all resources associated with it. Be cautious when using this command, as it will permanently delete all resources within the namespace.

Switching Context to a Namespace

To switch the current context to a specific namespace, you can use:

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

This command sets the current context to the specified namespace, allowing you to work within that namespace without needing to specify it in every command.

Accessing Resources in a Namespace

When accessing resources within a specific namespace, you can use the -n or --namespace flag:

kubectl get pods -n dev  # --namespace dev

This command lists all pods in the dev namespace. You can replace pods with any other resource type, such as services, deployments, etc.

kubectl get pods --all-namespaces  # -A

This command lists all pods across all namespaces in the cluster.

Resource Quotas in Namespaces

You can set resource quotas for a namespace to limit the amount of resources (CPU, memory, etc.) that can be used by the resources within that namespace. Here is an example of a resource quota definition:

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"

This example sets a resource quota for the dev namespace, limiting the total CPU and memory requests and limits for all resources within that namespace.

kubectl create -f resource-quota.yaml

This command creates the resource quota defined in the resource-quota.yaml file.