DevOps Classroomnotes 10/Jul/2022

K8s Storage Solutions

• Volumes: k8s Volume has a lifecycle equal to Pod. Once the Pod is deleted, the data will be lost
• Persistent Volumes: These volumes have lifecylce independent of Pod, So data will not be lost
• To create Persitent Volumes, We have two options
  • Manual Provisioning: In this case we need to manually create the storage to be used by the k8s cluster
  • Dynamic Provisioning: In this K8s will try to automatically create the storage based on the details provided. We prefer this approach on clouds
• K8s has the following types of persistent volumes Refer Here
• In K8s Storage Class provides a way for administrators to describe the classes of storage.
• If you are using managed k8s, it will already have some storage classes defined
  • aks
    
  • eks
• In K8s, we need to understand the relation between storage classes, Persistent Volumes and Persistent Volume Claims
• What is Persistent Volume Claim (PVC) => PVC is request for platform to create a persitent volume (PV) and attach it to your pods.
• Storage classes define the details (hardware details(ssd/hdd/block/file))

Pod -> PVC -> PV -> Target Machine (Type of this is defined by SC)

• When we are using the volume to mounted on multiple pods Refer Here
• Refer Here for the changeset containing changes to create a PVC which create a PV of size 1 GB of type managed-premium
  
  
  
• Refer Here for the same in AWS
  
  
• Stateful Sets: For storage solutions, where each instance of the application in Pod requires its own private volume then, we go for stateful sets. Stateful sets use PVC to claim PV.
  
• Refer Here to view the journey of the application from code to k8s.

Helm

• Helm is a package-manager for k8s.
• When we want to create a package for our application, we create helm-chart. This package uses go-template syntax Refer Here
• Refer Here to install helm
• Refer Here for bitnami repo
• Lets install jenkins using help Refer Here

Note

• Creating Elastic Kubernetes Service Refer Here
• Install AWS CLI Refer Here
• Creating an IAM User: Refer Here
• Installing eksctl Refer Here
• Installing kubectl Refer Here
• To create cluster the command is eksctl create cluster --name my-cluster --region region-code --version 1.22 --vpc-private-subnets subnet-ExampleID1,subnet-ExampleID2 --without-nodegroup
• Create a VPC using cloudformation template Refer Here. Make a note pf private subnet ids
• Create a node group

eksctl create nodegroup \
  --cluster qt-cluster \
  --region us-west-2 \
  --name al-nodes \
  --node-type t3.medium \
  --nodes 2 \
  --nodes-min 2 \
  --nodes-max 4 \
  --ssh-access \
  --ssh-public-key monitoring \
  --node-private-networking