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Namespace

 

As in many other platforms, there is normally more than one user (or team) working on a Kubernetes cluster. Suppose a pod named webserver1 has been built by a devops department, but when sales department attempts to launch a pod with the same name, the system will give an error:

Error from server (AlreadyExists): error when creating "webserver1.yaml": pods "webserver1" already exists

Kubernetes won’t allow the same object name for the Kubernetes resources to appear more than once in the same scope.

Namespaces provide the scope for the Kubernetes resource like project/tenant in OpenStack. Names of resources need to be unique within a namespace, but not across namespaces. It’s a natural way to divide cluster resources between multiple users.

Kubernetes starts with three initial namespaces:

  • default:The default namespace for objects with no other namespace.

  • kube-system: The namespace for objects created by the Kubernetes system.

  • kube-public: Initially created by kubeadm tool when deploying a cluster. By convention the purpose of this namespace is to make some resources readable by all users without authentication. It exists mostly in Kubernetes clusters boot-stapped with the kubeadm tool only.