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02-02 Kubernetes namespaces

Pods in a Kubernetes are located in namespaces, a grouping used to organise and isolate pods per team, product, or environment.

The different namespaces associated to your pods are visible when running kubectl get pods --all-namespaces.

We will create and use our own namespace to deploy our application and leave kube-system as the namespace for Kubernetes' internal resources.

Create a namespace

Create a namespace and name it after your team:

# Windows only
$env:TEAM_NAME="[team-name-placeholder]"
kubectl create namespace $env:TEAM_NAME

# MacOS only
export TEAM_NAME=[team-name-placeholder]
kubectl create namespace ${TEAM_NAME}

You have just created your first Kubernetes resource! List all the namespaces to confirm that your namespace has been created:

kubectl get namespaces

The output should be similar to this:

kubectl get namespaces
NAME              STATUS   AGE
my-ns             Active   1m
default           Active   3d22h
kube-node-lease   Active   3d22h
kube-public       Active   3d22h
kube-system       Active   3d22h

Note: many Kubernetes resources support both the plural and singular versions as well as a shorthand. For example, kubectl get ns, kubectl get namespace and kubectl get namespaces are all equivalent.

If you want to filter the output of kubectl to only one namespace (without having to always pass the -n option), permanently save the namespace in your kubectl context:

# Windows only
kubectl config set-context --current --namespace=$env:TEAM_NAME

# MacOS only
kubectl config set-context --current --namespace=${TEAM_NAME}

A namespace is an object type which we could have created with a YAML definition instead of using the kubectl create command.

Dump the current namespace with:

# Windows only
kubectl get ns $env:TEAM_NAME --output yaml

# MacOS only
kubectl get ns ${TEAM_NAME} --output yaml

The output should be similar to:

apiVersion: v1
kind: Namespace
metadata:
  creationTimestamp: "2020-04-20T03:31:45Z"
  name: [replace-team-name-here]
  resourceVersion: "1536018"
  selfLink: /api/v1/namespaces/will
  uid: d698cb1b-24ba-4f0f-8d36-aba334e3418b
spec:
  finalizers:
  - kubernetes
status:
  phase: Active

We will use here the YAML export to create our own YAML definition of the namespace and save it into ns.yml with the following content:

apiVersion: v1
kind: Namespace
metadata:
  name: [replace-team-name-here]

As you can see, we've removed any of the metadata shown in the exported version to create our own YAML definition of a namespace.

Delete the namespace with:

# Windows only
kubectl delete ns $env:TEAM_NAME

# MacOS only
kubectl delete ns ${TEAM_NAME}

And recreate it from a YAML file:

kubectl apply -f ns.yml

This command has re-created the namespace from a YAML definition that can be know kept in code.