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18-Namespaces.md

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Namespaces

In this section, we will take a look at Namespaces

So far in this course we have created Objects such as PODs, Deployments and Services in our cluster. Whatever we have been doing we have been doing in a NAMESPACE.

  • This namespace is the default namespace in kubernetes. It is automatically created when kubernetes is setup initially.

    ns

  • You can create your own namespaces as well.

    ns3

  • To list the pods in default namespace

    $ kubectl get pods

  • To list the pods in another namespace. Use kubectl get pods command along with the --namespace flag or argument.

    $ kubectl get pods --namespace=kube-system

    ns8

  • Here we have a pod definition file, when we create a pod with pod-definition file, the pod is created in the default namespace.

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
     app: myapp
     type: front-end
spec:
  containers:
  - name: nginx-container
    image: nginx

$ kubectl create -f pod-definition.yaml

  • To create the pod with the pod-definition file in another namespace, use the --namespace option.

    $ kubectl create -f pod-definition.yaml --namespace=dev

    ns9

  • If you want to make sure that this pod gets you created in the dev env all the time, even if you don't specify in the command line, you can move the --namespace definition into the pod-definition file.

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  namespace: dev
  labels:
     app: myapp
     type: front-end
spec:
  containers:
  - name: nginx-container
    image: nginx

ns10

  • To create a new namespace, create a namespace definition as shown below and then run kubectl create
apiVersion: v1
kind: Namespace
metadata:
  name: dev

$ kubectl create -f namespace-dev.yaml

Another way to create a namespace

$ kubectl create namespace dev

ns11

  • By default, we will be in a default namespace. To switch to a particular namespace permenently run the below command.

    $ kubectl config set-context $(kubectl config current-context) --namespace=dev

  • To view pods in all namespaces

    $ kubectl get pods --all-namespaces

    ns12

  • To limit resources in a namespace, create a resource quota. To create one start with ResourceQuota definition file.

apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: dev
spec:
  hard:
    pods: "10"
    requests.cpu: "4"
    requests.memory: 5Gi
    limits.cpu: "10"
    limits.memory: 10Gi

$ kubectl create -f compute-quota.yaml

ns13

K8s Reference Docs: