By default, Kubernetes has created a Namespace named default. All the objects created without specifying Namespaces will be put into the default Namespace. Kubernetes will also create another initial Namespace called kube-system for locating Kubernetes system objects, such as an add-on or overlay network. Try to list all the Namespaces:

// check all Namespaces, "ns" is the resource abbreviation of Namespace
$ kubectl get ns
NAME          STATUS    AGE
default       Active    15d
kube-public   Active    15d
kube-system   Active    15d

You may find an additional Namespace, kube-public, listed at the initial stage. It is designed for presenting some public configurations for even users without permission to access the Kubernetes system. Both of the provisioning tools, minikube and kubeadm, will create it while booting the system up.

The name of a Namespace must be a DNS label and follow the following rules:

• At most, 63 characters
• Matching regex [a-z0-9]([-a-z0-9]*[a-z0-9])