What does a kubernetes namespace represents in cluster?

Question

What is the physical representation of a namespace in cluster (I am using AWS) is it an EC2 server?

Can someone help me understand by giving a metaphor of what is the physical representation of:

1. Cluster
2. Namespace
3. Pods
4. Containers

Answer 1

Let's think of namespace as linux file system and ignore the fact of mounted directories for the sake of this question:

/srv => namespace-1
/var => namespace-2
/mnt => namespace-3
/bin => namespace-4

• All these 4 directories belongs to same /
• Inside a directory, you can have different type of files
• If you do ls /srv you won't see files in /var
• Different users can have different type of permissions on each directory

Now let's apply above 4 points in from the view of k8s namespace

• All these 4 namespaces belongs to same kubernetes cluster
• Inside a namespace, you can have different type of kubernetes objects
• If you do kubectl get deployments from namespace-1, you won't see deployments in namespace-2
• Different users can have different type of authorization on each namespaces

Answer 2

The short answer is - there is no physical representation of a namespace.

A namespace is a high-level abstraction that logically groups and manages Kubernetes resources (for example by type of environment development/staging/production). This helps in separating resources in the way that a resource from one namespace does not have access to the resources in other namespaces.

A cluster is a group of machines.

A container represents a real docker container running in one of the cluster nodes. You could assume a virtual image running inside a physical machine.

A pod represents group of containers (usualy 1 container, but can be more in case of sidecar deployment) deployed from single deployment resource (Deployment, ReplicaSet etc).