Difference between Kubernetes namespace and Linux namespaces?
There is no relationship to linux namespace.Kubernetes namespace is a logical construct to segregate cluster resources(such as pods, secrets) between multiple users. You can apply RBAC using role and rolebinding which defines who can do what in which namespace. That's how the isolation is achieved using namespaces. Internally the cluster resources are stored in ETCD(a key value store) and kubernetes API server allows or denies a user's request to perform CRUD operations on the cluster resources based what has been defined in RBAC policy. Interestingly if you get access to ETCD somehow then you can do everything across all namespaces. So the control is at the Kubernetes API Server layer.