What is Kubernetes (k8s)

Its a open source container orchestration tool designed to automate, deploying, scaling and operating containerized applications. Its a distributed system. Can use different container runtimes.

Key features:

1. Declarative configurations
2. Deploy Containers
3. Wire up networks
4. Expose and scale services
5. Atuomated deployment rollout and roolback
6. RBAC
7. Persistent volume management
8. Seamless horizontal scalling
9. Supports Linux & Windows Clusters

K8s Terms

• Clusters
• Nodes (master & worker)
• Pods
• Services
• Deployments

Other tools and Competitiors

1. DC/OS
2. Amazon ECS
3. Docker Swarm Mode

Deploying Kubernetes

• Docker Desktop
• Minikube
• kubeadm

K8s Architecture

• Its a container orchestration tool
• Composed of group of Nodes
• Conatiners run in a Pod
• Nodes are machine in clustres
• Control plane run's on master node and schedules containers on thde nodes
• Pod can have one or more containers
• K8s service exposes Pods to Cluster and outside them

Imperative Commands

Find all pods in a default namespace

kubectl get pods -n default

Create a pod redis with label name as ninad and using with exposing port 8080

kubectl run redis --image=redis -l name=ninad --port 8080

Create deployment with name nginx-deploy and image nginx with 5 replicas in namespace development

kubectl create deploy nginx-deploy --image=redis --replicas=5 -n development

Config Maps

kubectl get configmaps kubectl create configmap webapp-config-map --from-literal=APP_COLOR=darkblue

Secrets

kubectl get secrets kubectl describe secret kubectl create secret generic some-secret --from-literal=SOME_VAR=SomeTopSecret --from-literal=ANOTHER_VAR=SomeAnotherValue

Get the Pod Definition in yaml format

kubectl get pod pod-name -o yaml > pod-definition.yaml

Get details about pods definition file format and object

kubectl explain pods --recursive kubectl explain pods --recursive | less kubectl explain pods --recursive | grep -A10 envFrom

Get Volumnes

kubectl get pv pvc

Common multi container patterns

1. Sidecar pattern
2. Ambassador pattern
3. Adapter pattern

Tips and tricks for kubectl

kubectl completion --help

Enable: source < (kubectl completion bash) echo "source < (kubectl completion bash)" >> ~/.bash_profile

Press tab or press tab twice

kubectl

kubectl get nodes

pods = po

--sort-by='{.metadata.creationTimestamp}'

kubectl create namespace tricks -o yaml --dry-run

kubectl get pod -n app -o yaml --export | wcl -l

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References

• https://kubernetes.io/docs/home/
• https://www.cncf.io/certification/ckad/