5. K8s Namespaces

Namespace

• Organize resources in namespaces

• Virtual clusters inside k8 cluster

• 4 Namespaces by default

• kubernetes-dashboard only with minikube

1. kube-system

   • Do not create or modify in kube-system

   • Used by system processes

   • Master or kubectl processes

2. kube-public

   • Publically accessible data

   • A configmap, which contains cluster information

3. kube-node-lease

   • heartbeats of nodes

   • each node has associated lease of object in namespace

   • determines the availability of node

4. default

   • resources you create are located here

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Creating Namespace

Using CLI

kubectl create namespace <my-namespace>

Using Config File

Add namespace attribute in metadata.

apiVersion: v1
kind: ConfigMap
metadata:
	name: mysql-configmap
	namespace: my-namespace
data:
	db_utl: mysql-service.database

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Why to use namespace

1. Resources goruped in namespace

• All resources are created in default namespace

• Overtime, default namespace will be filled with different components

• Difficult to overview the namespace at that time

• Should not use for smaller projects

2. Conflicts: many teams, same application

• Two teams use same cluster and first team deploy app named my-app, second team also uses same same of deployment, hence they override previous team deployment

• Each team should use their own namespace to avoid disruption

3. Resource Sharing

1. Staging and Deployment

• Reuse the common components in both environments like logging cluster

2. Blue/Green Deployment

• Two different versions of production like v1 and v2

• They may need to use same resources

4. Access and Resource Limits on Namespaces

• We can give Team A access to their own namespace and vice versa

• They can't access other team's namespace

• We can also limit cpu, ram, storage resources per namespace using resource quota

Services which can't be accessed from another namespace

Since we cant access most resources from another namespace, simple things like ConfigMap and Secrets should be regenerated in each namespace causing duplication

Services which can be accessed from another namespace

• Service can be accessed from another namespace

• In ConfigMap definitation, the db_url will contains service name along with namespace name

Components which can't be created within namespace

• Some resources live globally inside a cluster

• you cant isolate them

• Examples are Volumes and Nodes

• Can be listed by kubectl api-resources --namespaced=false and vice versa

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Changing Active Namespace

$ yay kubectx
$ kubens
$ kubens my-namespace

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