The kubernetes-training from cueo

kubernetes-training's Introduction

Kubernetes Training

Notes

Kubernetes

Node = Bare metal machine
Add context.namespace in kube config to override default namespace
kubectly apply should be used always (create / update)
Use -w flag to watch the change in the resources

Pods

Each pod have their own ip
Pods communicated without NAT
One node can have pods across NS

Replica Set

Maintain a set of pod in a stable state
Specify a number of pods, on deletion of a pod another pod automatically comes up

Deployment

Useful for rolling deployements
- If we want to move to a newer version of the app
If we don't want rolling update for some reason, we can use Recreate strategy in spec.strategy.type: Recreate

Label

Can be attached to pods for organizing purposes

Example yaml for Pod

apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
    containers:
    - name: myc
      image: nginx:alpine

Commands

# Create pod from yaml (on default namespace)
kubectl create -f pod.yaml

# Create a namespace
kubectl create namespace mmayank

# Create pod on a given namespace
kubectl create -f pod.yaml -n mmayank

# Get list of pods on a NS
kubectl get pods -n mmayank

# Get list of pods with node, IP info
kubectl get pods -n mmayank -o wide

# Describe pod on a NS
kubectl describe pods -n mmayank

# Delete a pod
kubectl delete pod <pod-name>

# Create a replicaset
kubectl apply -f yaml/replicatset.yaml

# Delete a replicaset
kubectl delete rs <replicaset-name>

# Scale on the fly
kubectl scale deploy/nginx-deploy --replicas=2

# Labels
kubectl get pods --show-labels
kubectl get pods -l app=nginx
kubectl get pods -l app=!nginx
kubectl get pods -l app

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