Creating a Pod inside a Namespace

 Creating a Pod inside a Namespace

We are going to understand what is namespace in programming and what is namespace in Kubernetes world. Both are actually very much same. So today we'll talk about the namespace ,how to create it, check it and creating a Pod in a namespace.

Namespace

A namespace is set of signs or names that are used to identify and refer to objects of various kinds. A namespace ensures that all of the objects have unique name so that they can be easily identified. You can 

correlate this with schema in SQL server database where you can have multiple  tables with same name but in different schema. 

Similarly you can have multiple pods with same name but in different namespace.

How to check all available namespaces?

You can run kubectl get namespaces to get all available namespaces on cluster.

kubectl get namespaces

NAME              STATUS   AGE

default           Active   2d

kube-public       Active   2d

kube-system       Active   2d

You can also run kubectl get ns , where ns is short form of namespace.

How to create a namespace

To create a namespace you need to run kubectl create namespace namespace_name

kubectl create namespace test

namespace/test created

kubectl get namespaces         

NAME              STATUS   AGE

default           Active   82d

kube-public       Active   82d

kube-system       Active   82d

test              Active   5s

You can see test namespace has been created. 

Now you'll notice what are these namespaces other than test. I didn't create them. Let me explain.

• kube-system: Namespace for objects created by kubernetes system
• default: It's default namespace when you don't specify name then objects will be created in default namespace
• kube-public: This is created automatically and readable by all users. This namespace is mostly reserved for cluster usage.

Let' create a Pod in test namespace now using below commands.

kubectl run mypod --image=nginx -n test

kubectl run mypod --image=nginx -n test

pod/mypod created

Let's check the pod and make sure you look at test namespace.

kubectl get pods -n test

NAME    READY   STATUS    RESTARTS   AGE

mypod   1/1     Running   0          2m10s

I have created mypod in prod namespace as well. So we can have an application with same name but in different namespace.

kubectl run mypod --image=nginx -n prod

pod/mypod created

kubectl get pods -n prod               

NAME    READY   STATUS    RESTARTS   AGE

mypod   1/1     Running   0          14s

Conclusion

Namespace is very useful when deploying your application on cluster. It's always a best practice to create a namespace and deploy your application. You can think of a scenario where one team creates a pod with name testPod and other team also tries to name a pod testPod. So in this case Pod creation will be failed due to duplicate name. So best practice says create your pod inside a namespace. 

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