Namespaces

A real cluster is shared by many teams and many apps. Without some organisation, it would become a messy room where everyone's things are mixed together. Namespaces are the solution. In this lesson, you will see how they divide one cluster into separate, tidy spaces.

• One cluster, many teams
• Namespaces keep things apart
• Like folders on a computer

What a namespace is

A namespace is a virtual folder inside a cluster. Objects in one namespace are separate from those in another, so two teams can both have a pod called web, without any clash. Namespaces are also the place to attach rules, like how much memory a team may use, or who may access what. Kubernetes starts with four, default, where your objects go if you do not choose, kube system, for the cluster's own parts, kube public, and kube node lease.

Working with namespaces

Let's try. We create a namespace called shop. Then we run a pod inside it, using dash n, the namespace flag. Now we list pods. In the default namespace, there is nothing. The pod lives in shop, so we must ask for it with dash n shop. And the capital A flag, shows pods from all namespaces together. If you forget dash n, and see nothing, remember to check your namespace first, it is the most common beginner surprise.

kubectl create namespace shop
namespace/shop created
kubectl run web --image=nginx:1.27 -n shop
pod/web created
kubectl get pods
No resources found in default namespace.
kubectl get pods -n shop
NAME   READY   STATUS    RESTARTS   AGE
web    1/1     Running   0          12s
kubectl get pods -A | head -6
NAMESPACE     NAME                          READY   STATUS    RESTARTS      AGE
kube-system   coredns-66bc5c9577-m52m5      1/1     Running   2 (15m ago)   16m
kube-system   etcd-k8s                      1/1     Running   0             16m
kube-system   kindnet-blfp9                 1/1     Running   0             15m
kube-system   kindnet-glr5z                 1/1     Running   0             16m
kube-system   kindnet-mrj8p                 1/1     Running   0             16m

Switching your default

Typing dash n every time is tiring. You can change your default namespace, with the config command. After we set the current context to the shop namespace, a plain kube control get pods now shows the shop pod. That is convenient, but also dangerous, because you may forget where you are, and delete something in the wrong place. Many teams use a helper to show the current namespace in their prompt.

kubectl create namespace shop
namespace/shop created
kubectl run web --image=nginx:1.27 -n shop
pod/web created
kubectl config set-context --current --namespace=shop
Context "k8s" modified.
kubectl get pods
NAME   READY   STATUS    RESTARTS   AGE
web    1/1     Running   0          13s
kubectl config set-context --current --namespace=default
Context "k8s" modified.

Summary