Upgrade & Secure Your Future with DevOps, SRE, DevSecOps, MLOps!

We spend hours on Instagram and YouTube and waste money on coffee and fast food, but won’t spend 30 minutes a day learning skills to boost our careers.
Master in DevOps, SRE, DevSecOps & MLOps!

Learn from Guru Rajesh Kumar and double your salary in just one year.


Get Started Now!

Kubernetes

Kubernetes Commands: kubectl run – Tutorials and Examples

July 26, 2019 comments off 
#Imperatively working with your cluster. Run will "generate" a Deployment by default.
#This is pulling a specified image from Google's container registry.
#kubectl run, will convert a pod creation into a "Deployment generation"
#http://kubernetes.io/docs/user-guide/kubectl-conventions/#generators 
kubectl run hello-world --image=gcr.io/google-samples/hello-app:1.0

#But let's deploy a single pod too...
kubectl run hello-world-pod --image=gcr.io/google-samples/hello-app:1.0 --generator=run-pod/v1

#Let's follow our pod and deployment status
kubectl get pods
kubectl get deployment
kubectl get pods -o wide

#Remember, k8s is a container orchestrator and it's starting up containers on Nodes.
#Open a second terminal and ssh into the node that hello-world pod is running on.
ssh aen@c1-node1
sudo docker ps
exit

#Back on the Master, we can pull the logs from the container. Which is going to be anything written to stdout. 
#Maybe something went wrong inside our app, and our pod won't start. This is useful for troubleshooting.
kubectl logs hello-world-pod

#Starting a process inside a container inside a pod.
#We can use this to launch any process as long as the executable/binary is in the container.
#Launch a shell into the container. Callout that this is on the *pod* network.
kubectl exec -it hello-world-pod  -- /bin/sh
hostname
ip addr
exit

#Remember that first kubectl run we executed, it created a Deployment for us.
#Let's look more closely at the deployment
#Deployments are made of ReplicaSets!
kubectl get deployment hello-world
kubectl get replicaset
kubectl get pods

#Let's take a closer look at our pod.
#Walk through the pods Events...
#Name, Containers, Ports, Conditions, and Events. 
#Deployments are made of ReplicaSets!
kubectl describe deployment hello-world | more

#Let's see what describe can tell us about a deployed Pod.
#Check out the Name, Node, Status, Containers, and events.
kubectl get pods
kubectl describe pods $PASTEPODNAMEHERE | more

#Expose the Deployment as a Serivce.
#This will create a Service for the ReplicaSet behind the Deployment
#We are exposing our serivce on port 80, connecting to an application running on 8080 in our pod.
#Port: Interal Cluster Port, the Service's port. You will point cluster resources here.
#TargetPort: The Pod's Serivce Port, your application. That one we defined when we started the pods.
kubectl expose deployment hello-world --port=80 --target-port=8080

#Check out the IP: and Port:, that's where we'll access this service.
kubectl get service hello-world

#We can also get that information from using get
kubectl describe service hello-world

#Access the service inside the cluster
curl http://$SERVCIEIP:$PORT

#Access the pod's application directly, useful for troubleshooting.
kubectl get endpoints hello-world
curl http://$ENDPOINT:$TARGETORT

#Using kubectl to generate yaml or json files of our imperitive configuration.
kubectl get service hello-world -o yaml
kubectl get service hello-world -o json

#Exported resources are stripped of cluster-specific information.
kubectl get service hello-world -o yaml --export > service-hello-world.yaml
kubectl get deployment hello-world -o yaml --export > deployment-hello-world.yaml
ls *.yaml

more service-hello-world.yaml

#We can ask the API for more information about an object
kubectl explain service | more

#And drill down further if needed, includes very good explanation of what's available for that resource
kubectl explain service.spec | more
kubectl explain service.spec.ports
kubectl explain service.spec.ports.targetPort

#Let's remove everything we created imperitively and start over using a declarative model
kubectl delete service hello-world
kubectl delete deployment hello-world
kubectl delete pod hello-world-pod
kubectl get all

#Deploying applications declaratively
#we can use apply to create our resources from yaml.
kubectl apply -f deployment-hello-world.yaml
kubectl apply -f service-hello-world.yaml 

#This re-creates everything we created, but in yaml
kubectl get all

#scale up our deployment
vi deployment-hello-world.yaml
Change replicas from 1 to 2
     replicas: 2

#update our configuration with apply
kubectl apply -f deployment-hello-world.yaml

#And check the current configuration of our deployment
kubectl get deployment hello-world

#Repeat the curl access to see the load balancing of the HTTP request
kubectl get service hello-world
curl http://$SERVICEIP:PORT

#We can edit the resources "on the fly" with kubectl edit. But this isn't reflected in our yaml. But is
#persisted in the etcd database...cluster store. Change 2 to 3.
kubectl edit deployment hello-world

#Let's clean up our deployment and remove everything
kubectl delete deployment hello-world
kubectl delete service hello-world

kubectl get all

Certification Courses

DevOpsSchool has introduced a series of professional certification courses designed to enhance your skills and expertise in cutting-edge technologies and methodologies. Whether you are aiming to excel in development, security, or operations, these certifications provide a comprehensive learning experience. Explore the following programs:

DevOps Certification, SRE Certification, and DevSecOps Certification by DevOpsSchool

Explore our DevOps Certification, SRE Certification, and DevSecOps Certification programs at DevOpsSchool. Gain the expertise needed to excel in your career with hands-on training and globally recognized certifications.