Day 10/40
Kubernetes Namespace Explained
Video Link
@piyushsachdeva
Git Repository
My Git Repo
In this section, we're going to explain namespace in kubernetes.
It's a method by which single cluster used by and organization can be divided and categorized into multiple sub-clusters and managed individually. Different projects run simultaneously with different teams and departments work in parallel. source
When we create a workload like pod, deployment, service and so on without mentioning a namespace, it's actually created in default namespace.
By provisioning a kubernetes cluster, it creates own namespace named kube-system and all of its components will be in the kube-system namespace.
Each workload for example pod in a namespace can easily interact with each other with the hostname of their pod. But for interact to other namespace pod, they have to use FQDN.
(Photo from the video)
- Get all
namespaces:
root@localhost:~# kubectl get namespaces
NAME STATUS AGE
default Active 2d
kube-node-lease Active 2d
kube-public Active 2d
kube-system Active 2d
local-path-storage Active 2d
- Get all in
kube-systemnamespace:
root@localhost:~# kubectl get all --namespace=kube-system
NAME READY STATUS RESTARTS AGE
pod/coredns-7db6d8ff4d-bftnd 1/1 Running 1 (33h ago) 2d
pod/coredns-7db6d8ff4d-zs54d 1/1 Running 1 (33h ago) 2d
pod/etcd-lucky-luke-control-plane 1/1 Running 1 (33h ago) 2d
pod/kindnet-fbwgj 1/1 Running 1 (33h ago) 2d
pod/kindnet-hxb7v 1/1 Running 1 (33h ago) 2d
pod/kindnet-kh5s6 1/1 Running 1 (33h ago) 2d
pod/kube-apiserver-lucky-luke-control-plane 1/1 Running 1 (33h ago) 2d
pod/kube-controller-manager-lucky-luke-control-plane 1/1 Running 1 (33h ago) 2d
pod/kube-proxy-42h2f 1/1 Running 1 (33h ago) 2d
pod/kube-proxy-dhzrs 1/1 Running 1 (33h ago) 2d
pod/kube-proxy-rlzwk 1/1 Running 1 (33h ago) 2d
pod/kube-scheduler-lucky-luke-control-plane 1/1 Running 1 (33h ago) 2d
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 2d
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE
daemonset.apps/kindnet 3 3 3 3 3 kubernetes.io/os=linux 2d
daemonset.apps/kube-proxy 3 3 3 3 3 kubernetes.io/os=linux 2d
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/coredns 2/2 2 2 2d
NAME DESIRED CURRENT READY AGE
replicaset.apps/coredns-7db6d8ff4d 2 2 2 2d
Note we're using kind!
root@localhost:~# kubectl get all
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d
root@localhost:~# kubectl get all -n=default
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d
root@localhost:~# kubectl get all --namespace=default
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d
1. Create/Delete namespace
in declarative way:
---
apiVersion: v1
kind: Namespace
metadata:
name: demo
root@localhost:~# vim namespace.yaml
root@localhost:~# kubectl create -f namespace.yaml
namespace/demo created
root@localhost:~# kubectl get namespaces
NAME STATUS AGE
default Active 2d
demo Active 9s
kube-node-lease Active 2d
kube-public Active 2d
kube-system Active 2d
local-path-storage Active 2d
- Delete
namespace
root@localhost:~# kubectl delete ns/demo
namespace "demo" deleted
in imperative way:
root@localhost:~# kubectl create ns demo
namespace/demo created
root@localhost:~# kubectl get ns
NAME STATUS AGE
default Active 2d
demo Active 8s
kube-node-lease Active 2d
kube-public Active 2d
kube-system Active 2d
local-path-storage Active 2d
2. Create/Delete deployment in a namespace
root@localhost:~# kubectl create deploy nginx-demo --image=nginx -n demo
deployment.apps/nginx-demo created
root@localhost:~# kubectl get deploy
No resources found in default namespace.
root@localhost:~# kubectl get deploy -n demo
NAME READY UP-TO-DATE AVAILABLE AGE
nginx-demo 1/1 1 1 18s
3. Communicate between 2 namespaces:
root@localhost:~# kubectl get all -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
pod/nginx-test-574bc578fc-cj5fb 1/1 Running 0 5m16s 10.244.2.2 lucky-luke-worker2 <none> <none>
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d <none>
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
deployment.apps/nginx-test 1/1 1 1 5m16s nginx nginx app=nginx-test
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
replicaset.apps/nginx-test-574bc578fc 1 1 1 5m16s nginx nginx app=nginx-test,pod-template-hash=574bc578fc
root@localhost:~# kubectl get all -n demo -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
pod/nginx-demo-745b695d7d-hh28q 1/1 Running 0 7m48s 10.244.1.2 lucky-luke-worker <none> <none>
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
deployment.apps/nginx-demo 1/1 1 1 7m48s nginx nginx app=nginx-demo
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
replicaset.apps/nginx-demo-745b695d7d 1 1 1 7m48s nginx nginx app=nginx-demo,pod-template-hash=745b695d7d
- Both can have communication and we test it by
curlwithip
# curl 10.244.2.2
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
# curl 10.244.1.2
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
- Scaling both
deployment
root@localhost:~# kubectl scale --replicas=3 deploy nginx-test
deployment.apps/nginx-test scaled
root@localhost:~# kubectl scale --replicas=3 deploy nginx-demo -n demo
deployment.apps/nginx-demo scaled
root@localhost:~# kubectl get pod,deploy
NAME READY STATUS RESTARTS AGE
pod/nginx-test-574bc578fc-cj5fb 1/1 Running 0 14m
pod/nginx-test-574bc578fc-cqj5r 1/1 Running 0 10s
pod/nginx-test-574bc578fc-nxt4j 1/1 Running 0 10s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/nginx-test 3/3 3 3 14m
root@localhost:~# kubectl get pod,deploy -n demo
NAME READY STATUS RESTARTS AGE
pod/nginx-demo-745b695d7d-hh28q 1/1 Running 0 16m
pod/nginx-demo-745b695d7d-rp88f 1/1 Running 0 19s
pod/nginx-demo-745b695d7d-sc8rg 1/1 Running 0 19s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/nginx-demo 3/3 3 3 16m
- Creating
servicefor bothdeployment
(Photo from the video)
Test in default namespace:
root@localhost:~# kubectl expose --name svc-test deploy/nginx-test --port 80
service/svc-test exposed
root@localhost:~# kubectl get pod
NAME READY STATUS RESTARTS AGE
nginx-test-574bc578fc-cj5fb 1/1 Running 0 29m
nginx-test-574bc578fc-cqj5r 1/1 Running 0 15m
nginx-test-574bc578fc-nxt4j 1/1 Running 0 15m
root@localhost:~# kubectl exec -it nginx-test-574bc578fc-cj5fb -- sh
# cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
# curl svc-demo.demo.svc.cluster.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
Test in demo namespace:
root@localhost:~# kubectl expose --name svc-demo deploy/nginx-demo --port 80 -n demo
service/svc-demo exposed
root@localhost:~# kubectl get pod -n demo
NAME READY STATUS RESTARTS AGE
nginx-demo-745b695d7d-hh28q 1/1 Running 0 35m
nginx-demo-745b695d7d-rp88f 1/1 Running 0 19m
nginx-demo-745b695d7d-sc8rg 1/1 Running 0 19m
root@localhost:~# kubectl exec -it nginx-demo-745b695d7d-hh28q -n demo -- sh
# cat /etc/resolv.conf
search demo.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
# curl svc-test.default.svc.cluster.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
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