pelicin › devops › Kubernetes

Namespaces

You can split resources from a single cluster into multiple namespaces for organization. (For example, you want to split resources into "production," "QA," and "development" environments.)

Names of resources need to be unique within a namespace, but not across namespaces.

Also, cluster-wide objects like StorageClass, Nodes, or PersistentVolumes are not scoped by namespaces.

Namespace descriptor

A sample namespace descriptor looks like the following:

apiVersion: v1
kind: Namespace
metadata:
  name: custom-namespace

Working with namespaces

Unless you specify the namespace, you are working with the default namespace.

Creating a namespace

Send the namespace descriptor to the Kubernetes API server:

# If you create a descriptor named custom-namespace.yaml:
kubectl create -f custom-namespace.yaml

Listing namespaces

kubectl get namespaces
# NAME                   STATUS   AGE
# default                Active   3d
# kube-node-lease        Active   3d
# kube-public            Active   3d
# kube-system            Active   3d

Listing pods in a namespace

Use -n <namespace> or --namespace <namespace>:

kubectl get pod -n kube-system
# NAME                               READY   STATUS    RESTARTS        AGE
# coredns-6d4b75cb6d-zfl6s           1/1     Running   8 (4h9m ago)    3d
# etcd-minikube                      1/1     Running   8 (4h9m ago)    3d
# kube-apiserver-minikube            1/1     Running   9 (4h9m ago)    3d
# kube-controller-manager-minikube   1/1     Running   8 (4h9m ago)    3d
# kube-proxy-tdqvj                   1/1     Running   8 (4h9m ago)    3d
# kube-scheduler-minikube            1/1     Running   9 (4h9m ago)    3d
# storage-provisioner                1/1     Running   14 (4h6m ago)   3d

Managing objects in a namespace

Do either one of the following:

  • add namespace field to the metadata section of the descriptor, OR
  • use -n <namespace> or --namespace <namespace>:
kubectl create -f kubia-manual.yaml -n custom-namespace
# pod "kubia-manual" created

References

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