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Niraj Pradhan
Niraj Pradhan

Posted on • Updated on

All about namespace and deploy docker image to namespace in k8s cluster.

Namespace

In kubernetes cluster, we have to isolate, manage, organize, allocate and secure various resources. Namespace are the way or mechanism to manage the resources such as pod,deploy, service, etc. It provides virtual cluster within a single cluster. It provides the proper optimization of resources such as seperation of user based on role, allows teams to share across a cluster. Basically, it logically isolates the resources with concern of security.

Four namespaces are created automatically while setting up cluster.

~ kubectl get namespaces
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Output

NAME                   STATUS   AGE
default                Active   11d
kube-node-lease        Active   11d
kube-public            Active   11d
kube-system            Active   11d
kubernetes-dashboard   Active   11d
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  • default: All the resources deployment without a namespace are deployed under default namespace.
  • kube-node-lease: All nodes have an Lease object in this namespace.
  • kube-public: kube-public is available to all users with read-only-access and reserved for system usage.
  • kube-system: This namespace holds all the configurations and deployments.
  • kubernetes-dashboard: Kubernetes dashboard is a web based user interface for managing cluster and its resources. It is not created by default as other namespace but created while setting up kubernetes dashboard. Kubernetes dashboard is deployed in kubernetes-dashboardnamespace.

Creating namespace

We can create namespace in different ways with kubectl create namespace <namespace-name> or with yaml file.

Naming conventions

  • the characters must be less than or equal to 63
  • must start and end with an alphanumeric character
  • must consist of lower case alphanumeric characters or "-"

Method 1 : Direct create with CLI

~ kubectl create namespace user

  namespace/user created
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It will create user namespace in kubernetes cluster. We can use ns as shortcut for namespace.
Lets check,

~ kubectl get ns
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Output

NAME                   STATUS   AGE
default                Active   12d
kube-node-lease        Active   12d
kube-public            Active   12d
kube-system            Active   12d
kubernetes-dashboard   Active   12d
user                   Active   27s
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~ kubectl create namespace qa --dry-run=client

  namespace/qa created (dry run)
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With --dry-run=client , it will not deploy namespace to server but just simulate it.

Lets check,

~ kubectl get ns
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Output

NAME                   STATUS   AGE
default                Active   12d
kube-node-lease        Active   12d
kube-public            Active   12d
kube-system            Active   12d
kubernetes-dashboard   Active   12d
user                   Active   27s
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We see that, qa namespace is not deployed to the server.

Method 2 : Create with yaml file

We can also create namespace by writing scripts in yaml file.
Lets create yaml file.

~ vim qa.yaml
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apiVersion: v1
kind: Namespace
metadata:
  name: qa
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We can apply the scripts of qa.yaml with command as:

~ kubectl create -f qa.yaml

   namespace/qa created
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or

~ kubectl apply -f qa.yaml

  namespace/qa created
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Now this qa namespace is created and deployed to server as well.

Lets check,

~ kubectl get ns
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Output

NAME                   STATUS   AGE
default                Active   12d
kube-node-lease        Active   12d
kube-public            Active   12d
kube-system            Active   12d
kubernetes-dashboard   Active   12d
qa                     Active   89s
user                   Active   64m
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Deploy resource to namespace

In the previous post, we have published a container image nirajpdn/react-app:v1 and nirajpdn/react-app:v2 to docker hub. Lets deploy that image to namespace.

~ kubectl run react-app --image=nirajpdn/react-app:v1
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It will deploy that image to the default namespace by default because we haven't specified the namespace to deploy.

~ kubectl get po
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It will shows all the pods in the default namespace.

Output

NAME        READY   STATUS    RESTARTS   AGE
react-app   1/1     Running   0          3m1s
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Lets check the pods with specifying namespace.

~ kubectl get po -n qa

  No resources found in qa namespace.
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Alright, we haven't deployed any resource to the qa namespace.

~ kubectl run react-app --image=nirajpdn/react-app:v1 -n qa
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~ kubectl get po -n qa
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Output

NAME        READY   STATUS    RESTARTS   AGE
react-app   1/1     Running   0          11s
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Finally we have successfully deployed docker image to the kubernetes cluster.

~ kubectl describe po react-app -n qa
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Output

Name:         react-app
Namespace:    qa
Priority:     0
Node:         minikube/192.168.49.2
Start Time:   Mon, 20 Jun 2022 02:17:59 +0545
Labels:       run=react-app
Annotations:  <none>
Status:       Running
IP:           172.17.0.3
IPs:
  IP:  172.17.0.3
Containers:
  react-app:
    Container ID:   docker://f956442127390f513901c6aa7049de6be0d95f2f4fa81257ec67827e7268c6c7
    Image:          nirajpdn/react-app:v1
    Image ID:       docker-pullable://nirajpdn/react-app@sha256:dcfb3c960e0c6777a098578564ca1deb547e73debcc8aa59702d8ad43dca75c6
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Mon, 20 Jun 2022 02:18:00 +0545
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-6tdhw (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-6tdhw:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  15s   default-scheduler  Successfully assigned qa/react-app to minikube
  Normal  Pulled     14s   kubelet            Container image "nirajpdn/react-app:v1" already present on machine
  Normal  Created    14s   kubelet            Created container react-app
  Normal  Started    14s   kubelet            Started container react-app
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We can also delete resource with command:

~ kubectl delete po react-app -n qa
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It will delete the react-app pods from qa namespace.

~ kubectl get po -n qa

  No resources found in qa namespace.
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Deleting namespace

We can delete namespace just by,

~ kubectl delete ns qa

  namespace "qa" deleted
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or if namespace is created with yaml file then we can also do as follows:

~ kubectl delete -f qa.yaml 

  namespace "qa" deleted
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While deleting namespace with delete command, all the resources associated with particular namespace will be deleted.

In next post we will discuss about ReplicaSet.

Discussion (2)

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bkpandey profile image
Balkrishna Pandey • Edited on

kubernetes-dashboard does not appear to be part of the default automated namespaces, I think.

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nirajpdn profile image
Niraj Pradhan Author • Edited on

I have mentioned that, namespace kubernetes-dashboard is not automatically created by default but it is created while setting up Kubernetes Dashboard in minikube or any cluster. Is it ok ?