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Kubernetes

A brief overview of Kubernetes

What is Kubernetes?

  • Kubernetes is a container orchestration platform designed to automate the deployment, scaling, and management of containerized applications.

Kubernetes Terminology

  • An application gets deployed (encapsulated) into a Pod which is a single instance of an application
  • Pods exist on a Node
  • Multiple Nodes form a Cluster

Kubernetes Deployment Example

  • A Kubernetes Deployment file is created in YAML and provides a declarative way to specify the desired state of an application and its associated resources
# A basic Kubernetes deployment file that deploys 2 (replicas) containers
​
apiVersion: apps/v1
kind: Deployment
metadata:
name: tylers-deployment
labels:
app: tylers-app
spec:
template:
metadata:
name: tylers-pod
lables:
app: tylers-app
spec:
containers:
- name: tylers-container
image: alpine:latest
replicas: 2
selector:
matchLabels:
app: tylers-app

Kubernetes Cheat Sheet

  • A handy list of common Kubernetes commands organized by type

Deployment Commands

# Deploy a container on a Pod
kubectl run <nameOfPod> --image <nameOfTheImageFromYourImageRepo>
# kubectl run nginx --image nginx
​
# Deploy from a yaml file (apply and create are interchangable)
kubectl apply -f <fileName>.yaml
​
# Deploy a deployment type file
kubectl apply -f <fileName>.yaml
​
# View deployment
kubectl get deployments
​
# Edit a deployment
kubectl edit deployments <deploymentName>
​
# Apply a new update
kubectl apply -f <fileName>.yaml
​
# View deployment status
kubectl rollout status deployment/<deploymentName>
​
# View deployment history
kubectl rollout history deployment/<deploymentName>
​
# Rollback a deployment
kubectl rollout undo deployment/<deploymentName>

Node Commands

# Get nodes in cluster
kubectl get nodes
​
# Get OS of running nodes
kubectl get nodes --output wide # other options exist too e.g., json'

Pod Commands

# Get Pods
kubectl get pods
​
# Get details of a Pod
kubectl describe pods # <podName>
​
# Delete a pod (or pods if more than one is specified)
kubectl delete pod <podName> # <podName2> <podName3>

Replica Commands

# Get number of replicasets
kubectl get replicasets
​
# Get details of replicasets
kubectl describe replicasets # <replicaset name>
​
# Delete a replicaset (or sets if more than one is specified)
kubectl delete replicasets <replicasetName> # <replicasetName2>
​
# Edit an existing replicaset (this should take effect after changing the file)
kubectl edit replicasets <replicasetName> # then change the number to replicate

Service Commands

# Create a service
kubectl create -f <serviceDefinitionFile>
​
# View services
kubectl get serivces

Troubleshooting Commands

# View pod logs
kubectl logs <podName> -n <namespace>

Useful Resources