kubernetes commands

Running application in deployment:

$kubectl create -f redis-deploy.yaml 
error: unable to recognize "redis-deploy.yaml": no matches for kind "Deployment" in version "apps/v1beta1

Then we check the required version for the deployment and we modify the yam file redis-deploy.yaml .

$kubectl explain deployment

KIND:     Deployment
VERSION:  apps/v1

Then we rerun the command:

$kubectl create -f redis-deploy.yaml
deployment.apps/redis created

Namespaces:

\W $kubectl create -f busybox.yaml
pod/busybox2 created
\W $kubectl create -f busybox.yaml
Error from server (AlreadyExists): error when creating "busybox.yaml": pods "busybox2" already exists

If we try to create the same pod, we will get an error but if we create a pod in a different namespace by modifying the namespace in the yaml file. The pod will be created

$kubectl create ns myspace    
namespace/myspace created
$vim busybox.yaml
$kubectl create -f busybox.yaml
pod/busybox2 created

We see that we have 2 busybox2 created in different Namespaces.

$kubectl get pods --all-namespaces 
NAMESPACE     NAME                               READY   STATUS    RESTARTS   AGE
default       busybox2                           1/1     Running   0          5m49s
default       redis-6fb5b985bc-9jl56             1/1     Running   0          2d22h
kube-system   coredns-74ff55c5b-bgtzz            1/1     Running   0          4d15h
kube-system   etcd-minikube                      1/1     Running   0          4d15h
kube-system   kube-apiserver-minikube            1/1     Running   0          4d15h
kube-system   kube-controller-manager-minikube   1/1     Running   0          4d15h
kube-system   kube-proxy-n9f56                   1/1     Running   0          4d15h
kube-system   kube-scheduler-minikube            1/1     Running   0          4d15h
kube-system   storage-provisioner                1/1     Running   2          4d15h
myspace       busybox2 

Application scalability: 1- We change the number of replicas of the deployment redis to 3 using the command kubectl edit deployments redis

$kubectl get deployments.apps 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
redis   1/1     1            1           2d22h
\W $
\W $kubectl edit deployments redis     
deployment.apps/redis edited
\W $kubectl get deployments.apps  
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
redis   3/3     3            3           2d22h

2. Usign scale command:

$kubectl scale --replicas=4 deployment redis          
deployment.apps/redis scaled
$kubectl get deployments.apps               
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
redis   4/4     4            4           2d22h

List the pods with IP adresse value

kubectl get pods -o wide
verybusy                 2/2     Running            0          12s   172.17.0.4    minikube