Updated: Aug 12, 2020
In the last article we studied about deployments in kubernetes. Now there can be scenarios where kubernetes cluster may be hosting different applications on the same cluster and resources need to be isolated.
Namespaces in Kubernetes are a way to isolate cluster resources.They can be thought about segregated regions inside a cluster.
Objects within a namespace share same set of resources and communicate with each other directly.
Whatever we have been doing in the last articles like creation of pods,services and deployments, we were doing it inside a namespace( By default the namespace used is the default namespace)
By default below namespaces are created at the time of cluster installation. We can create our own as well.
default The default namespace for objects with no other namespace
kube-system The namespace for objects created by the Kubernetes system
kube-public This namespace is created automatically and is readable by all users (including those not authenticated). This namespace is mostly reserved for cluster usage, in case that some resources should be visible and readable publicly throughout the whole cluster. The public aspect of this namespace is only a convention, not a requirement.
kube-node-lease This namespace for the lease objects associated with each node which improves the performance of the node heartbeats as the cluster scales.
[root@node1 ~]# kubectl get ns NAME STATUS AGE default Active 6d19h kube-node-lease Active 6d19h kube-public Active 6d19h kube-system Active 6d19h [root@node1 ~]# kubectl create ns demo-ns namespace/demo-ns created [root@node1 ~]# kubectl get ns NAME STATUS AGE default Active 6d19h demo-ns Active 2s kube-node-lease Active 6d19h kube-public Active 6d19h kube-system Active 6d19h
To change the current namespace
[root@node1 ~]# kubectl config set-context --current --namespace=demo-ns
Each namespace can have its own quota of resources
Services within the namespace can communicate with only the name but if communication needs to happen between the namespaces, then the namespace name must be appended with the service.
For listing/creating resources we have to mention the namespace as well
like kubectl get pods -n namespace_name.
Resource quota can be created as required as shown below.
## namespace-resource-quota.yaml apiVersion: v1 kind: ResourceQuota metadata: name: mem-cpu-demo spec: hard: requests.cpu: "1" requests.memory: 1Gi limits.cpu: "2" limits.memory: 2Gi ## Save and exit this file and execute below command kubectl create -f namespace-resource-quota.yaml
Alright that is it for this article. I hope you are loving our journey learning kubernetes. We will study the concept of services in the next article.